Merge PR #4904: Remove empty files and broken links
This commit is contained in:
Marko
committed by
Alexander Bezobchuk
Alexander Bezobchuk
parent
c441ce2fab
commit
f1adb7afd9
@@ -1,15 +0,0 @@
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# Accounts, Fees and Gas
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## Accounts
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## AnteHandler
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## Signatures
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## Fees
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## Gas
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## Gas Meter
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## Block Gas Meter
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+56
-76
@@ -29,11 +29,11 @@ The core parts listed above will generally translate to the following directory
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│ └── bank
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├── go.mod
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└── Makefile
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```
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```
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## Node Client
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## Node Client
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The Daemon, or Full-Node Client, is the core process of an SDK-based blockchain. Participants in the network run this process to initialize their state-machine, connect with other full-nodes and update their state-machine as new blocks come in.
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The Daemon, or Full-Node Client, is the core process of an SDK-based blockchain. Participants in the network run this process to initialize their state-machine, connect with other full-nodes and update their state-machine as new blocks come in.
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```
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^ +-------------------------------+ ^
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@@ -52,31 +52,30 @@ Blockchain Node | | Consensus | |
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| | | |
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v +-------------------------------+ v
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```
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The blockchain full-node presents itself as a binary, generally suffixed by `-d` for "daemon" (e.g. `appd` for `app` or `gaiad` for `gaia`). This binary is built by running a simple `main.go` function placed in `cmd/appd/`. This operation usually happens through the [Makefile](#dependencies-and-makefile).
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To learn more about the `main.go` function, [click here](./node.md#main-function).
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Once the main binary is built, the node can be started by running the `start` command. The core logic behind the `start` command is implemented in the SDK itself in the [`/server/start.go`](https://github.com/cosmos/cosmos-sdk/blob/master/server/start.go) file. The main [`start` command function](https://github.com/cosmos/cosmos-sdk/blob/master/server/start.go#L31) takes a [`context`](https://godoc.org/github.com/cosmos/cosmos-sdk/client/context) and [`appCreator`](#constructor-function-(`appCreator`)) as arguments. The `appCreator` is a constructor function for the SDK application, and is used in the starting process of the full-node.
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Once the main binary is built, the node can be started by running the `start` command. The core logic behind the `start` command is implemented in the SDK itself in the [`/server/start.go`](https://github.com/cosmos/cosmos-sdk/blob/master/server/start.go) file. The main [`start` command function](https://github.com/cosmos/cosmos-sdk/blob/master/server/start.go#L31) takes a [`context`](https://godoc.org/github.com/cosmos/cosmos-sdk/client/context) and [`appCreator`](<#constructor-function-(`appCreator`)>) as arguments. The `appCreator` is a constructor function for the SDK application, and is used in the starting process of the full-node.
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The `start` command function primarily does three things:
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1. Create an instance of the state-machine defined in [`app.go`](#core-application-file) using the `appCreator`.
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2. Initialize the state-machine with the latest known state, extracted from the `db` stored in the `~/.appd/data` folder. At this point, the state-machine is at height `appBlockHeight`.
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1. Create an instance of the state-machine defined in [`app.go`](#core-application-file) using the `appCreator`.
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2. Initialize the state-machine with the latest known state, extracted from the `db` stored in the `~/.appd/data` folder. At this point, the state-machine is at height `appBlockHeight`.
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3. Create and start a new Tendermint instance. Among other things, the node will perform a handshake with its peers. It will get the latest `blockHeight` from them, and replay blocks to sync to this height if it is greater than the local `appBlockHeight`. If `appBlockHeight` is `0`, the node is starting from genesis and Tendermint sends an `InitChain` message via the ABCI to the `app`, which triggers the [`InitChainer`](#initchainer).
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To learn more about the `start` command, [click here](./node.md#start-command).
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## Core Application File
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In general, the core of the state-machine is defined in a file called `app.go`. It mainly contains the **type definition of the application** and functions to **create and initialize it**.
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In general, the core of the state-machine is defined in a file called `app.go`. It mainly contains the **type definition of the application** and functions to **create and initialize it**.
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### Type Definition of the Application
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The first thing defined in `app.go` is the `type` of the application. It is generally comprised of the following parts:
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- **A reference to [`baseapp`](./baseapp.md).** The custom application defined in `app.go` is an extension of the `baseapp` type. `baseapp` implements most of the core logic for the application, including all the [ABCI methods](https://tendermint.com/docs/spec/abci/abci.html#overview) and the routing logic. When a transaction is relayed by Tendermint to the application, the latter uses `baseapp`'s methods to route them to the appropriate module.
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- **A list of store keys**. The [store](./store.md), which contains the entire state, is implemented as a multistore (i.e. a store of stores) in the Cosmos SDK. Each module uses one or multiple stores in the multistore to persist their part of the state. These stores can be accessed with specific keys that are declared in the `app` type. These keys, along with the `keepers`, are at the heart of the [object-capabilities model](../intro/ocap.md) of the Cosmos SDK.
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- **A list of module's `keepers`.** Each module defines an abstraction called `keeper`, which handles reads and writes for this module's store(s). The `keeper`'s methods of one module can be called from other modules (if authorized), which is why they are declared in the application's type and exported as interfaces to other modules so that they are only allowed to access the authorized functions.
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- **A reference to [`baseapp`](./baseapp.md).** The custom application defined in `app.go` is an extension of the `baseapp` type. `baseapp` implements most of the core logic for the application, including all the [ABCI methods](https://tendermint.com/docs/spec/abci/abci.html#overview) and the routing logic. When a transaction is relayed by Tendermint to the application, the latter uses `baseapp`'s methods to route them to the appropriate module.
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- **A list of store keys**. The [store](./store.md), which contains the entire state, is implemented as a multistore (i.e. a store of stores) in the Cosmos SDK. Each module uses one or multiple stores in the multistore to persist their part of the state. These stores can be accessed with specific keys that are declared in the `app` type. These keys, along with the `keepers`, are at the heart of the [object-capabilities model](../intro/ocap.md) of the Cosmos SDK.
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- **A list of module's `keepers`.** Each module defines an abstraction called `keeper`, which handles reads and writes for this module's store(s). The `keeper`'s methods of one module can be called from other modules (if authorized), which is why they are declared in the application's type and exported as interfaces to other modules so that they are only allowed to access the authorized functions.
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- **A reference to a `codec`.** The Cosmos SDK gives developers the freedom to choose the encoding framework for their application. The application's `codec` is used to serialize and deserialize data structures in order to store them, as stores can only persist `[]bytes`. The `codec` must be deterministic. The default codec is [amino](./amino.md).
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- **A reference to a [module manager](./modules.md#module-manager)**. The module manager is an object that contains a list of the application's module. It facilitates operations related to these modules, like registering [`routes`](./baseapp.md#routing), [query routes](#./baseapp.md#query-routing) or setting the order of execution between modules for various functions like [`InitChainer`](#initchainer), [`BeginBlocker` and `EndBlocker`](#beginblocker-and-endblocker).
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@@ -87,129 +86,116 @@ You can see an example of application type definition [here](https://github.com/
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This function constructs a new application of the type defined above. It is called every time the full-node is started with the [`start`](https://github.com/cosmos/cosmos-sdk/blob/master/server/start.go#L117) command. Here are the main actions performed by this function:
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- Instantiate a new application with a reference to a `baseapp` instance, a codec and all the appropriate store keys.
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- Instantiate all the [`keeper`s](#keeper) defined in the application's `type` using the `NewKeeper` function of each of the application's modules. Note that `keepers` must be instantiated in the correct order, as the `NewKeeper` of one module might require a reference to another module's `keeper`.
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- Instantiate the application's [module manager](./module-manager.md) with the [`AppModule`](#application-module-interface) object of each of the application's modules.
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- With the module manager, initialize the application's [`routes`](./baseapp.md#routing) and [query routes](./baseapp.md#query-routing). When a transaction is relayed to the application by Tendermint via the ABCI, it is routed to the appropriate module's [`handler`](#handler) using the routes defined here. Likewise, when a query is received by the application, it is routed to the appropriate module's [`querier`](#querier) using the query routes defined here.
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- With the module manager, register the [application's modules' invariants](./invariants.md). Invariants are variables (e.g. total supply of a token) that are evaluated at the end of each block. The process of checking invariants is done via a special module called the [`InvariantsRegistry`](./invariants.md#invariant-registry). The value of the invariant should be equal to a predicted value defined in the module. Should the value be different than the predicted one, special logic defined in the invariant registry will be triggered (usually the chain is halted). This is useful to make sure no critical bug goes unnoticed and produces long-lasting effects that would be hard to fix.
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- With the module manager, set the order of execution between the `InitGenesis`, `BegingBlocker` and `EndBlocker` functions of each of the [application's modules](#application-module-interface). Note that not all modules implement these functions.
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- Instantiate all the [`keeper`s](#keeper) defined in the application's `type` using the `NewKeeper` function of each of the application's modules. Note that `keepers` must be instantiated in the correct order, as the `NewKeeper` of one module might require a reference to another module's `keeper`.
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- Instantiate the application's [module manager](./module-manager.md) with the [`AppModule`](#application-module-interface) object of each of the application's modules.
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- With the module manager, initialize the application's [`routes`](./baseapp.md#routing) and [query routes](./baseapp.md#query-routing). When a transaction is relayed to the application by Tendermint via the ABCI, it is routed to the appropriate module's [`handler`](#handler) using the routes defined here. Likewise, when a query is received by the application, it is routed to the appropriate module's [`querier`](#querier) using the query routes defined here.
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- With the module manager, register the [application's modules' invariants](./invariants.md). Invariants are variables (e.g. total supply of a token) that are evaluated at the end of each block. The process of checking invariants is done via a special module called the [`InvariantsRegistry`](./invariants.md#invariant-registry). The value of the invariant should be equal to a predicted value defined in the module. Should the value be different than the predicted one, special logic defined in the invariant registry will be triggered (usually the chain is halted). This is useful to make sure no critical bug goes unnoticed and produces long-lasting effects that would be hard to fix.
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- With the module manager, set the order of execution between the `InitGenesis`, `BegingBlocker` and `EndBlocker` functions of each of the [application's modules](#application-module-interface). Note that not all modules implement these functions.
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- Set the remainer of application's parameters:
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+ [`InitChainer`](#initchainer): used to initialize the application when it is first started.
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+ [`BeginBlocker`, `EndBlocker`](#beginblocker-and-endlbocker): called at the beginning and the end of every block).
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+ [`anteHandler`](#baseapp.md#antehandler): used to handle fees and signature verification.
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- Mount the stores.
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- Return the application.
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- [`InitChainer`](#initchainer): used to initialize the application when it is first started.
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- [`BeginBlocker`, `EndBlocker`](#beginblocker-and-endlbocker): called at the beginning and the end of every block).
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- [`anteHandler`](#baseapp.md#antehandler): used to handle fees and signature verification.
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- Mount the stores.
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- Return the application.
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Note that this function only creates an instance of the app, while the actual state is either carried over from the `~/.appd/data` folder if the node is restarted, or generated from the genesis file if the node is started for the first time.
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Note that this function only creates an instance of the app, while the actual state is either carried over from the `~/.appd/data` folder if the node is restarted, or generated from the genesis file if the node is started for the first time.
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You can see an example of application constructor [here](https://github.com/cosmos/gaia/blob/master/app/app.go#L110-L222).
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### InitChainer
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The `InitChainer` is a function that initializes the state of the application from a [genesis file](./genesis.md) (i.e. token balances of genesis accounts). It is called when the application receives the `InitChain` message from the Tendermint engine, which happens when the node is started at `appBlockHeight == 0` (i.e. on genesis). The application must set the `InitChainer` in its constructor via the [`SetInitChainer`](https://godoc.org/github.com/cosmos/cosmos-sdk/baseapp#BaseApp.SetInitChainer) method.
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The `InitChainer` is a function that initializes the state of the application from a [genesis file](./genesis.md) (i.e. token balances of genesis accounts). It is called when the application receives the `InitChain` message from the Tendermint engine, which happens when the node is started at `appBlockHeight == 0` (i.e. on genesis). The application must set the `InitChainer` in its constructor via the [`SetInitChainer`](https://godoc.org/github.com/cosmos/cosmos-sdk/baseapp#BaseApp.SetInitChainer) method.
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In general, the `InitChainer` is mostly composed of the `InitGenesis` function of each of the application's modules. This is done by calling the `InitGenesis` function of the module manager, which in turn will call the `InitGenesis` function of each of the modules it contains. Note that the order in which the modules' `InitGenesis` functions must be called has to be set in the module manager using the `SetOrderInitGenesis` method. This is done in the [application's constructor](#application-constructor), and the `SetOrderInitGenesis` has to be called before the `SetInitChainer`.
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In general, the `InitChainer` is mostly composed of the `InitGenesis` function of each of the application's modules. This is done by calling the `InitGenesis` function of the module manager, which in turn will call the `InitGenesis` function of each of the modules it contains. Note that the order in which the modules' `InitGenesis` functions must be called has to be set in the module manager using the `SetOrderInitGenesis` method. This is done in the [application's constructor](#application-constructor), and the `SetOrderInitGenesis` has to be called before the `SetInitChainer`.
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You can see an example of an `InitChainer` [here](https://github.com/cosmos/gaia/blob/master/app/app.go#L235-L239).
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### BeginBlocker and EndBlocker
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The SDK offers developers the possibility to implement automatic execution of code as part of their application. This is implemented through two function called `BeginBlocker` and `EndBlocker`. They are called when the application receives respectively the `BeginBlock` and `EndBlock` messages from the Tendermint engine, which happens at the beginning and at the end of each block. The application must set the `BeginBlocker` and `EndBlocker` in its constructor via the [`SetBeginBlocker`](https://godoc.org/github.com/cosmos/cosmos-sdk/baseapp#BaseApp.SetBeginBlocker) and [`SetEndBlocker`](https://godoc.org/github.com/cosmos/cosmos-sdk/baseapp#BaseApp.SetEndBlocker) methods.
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The SDK offers developers the possibility to implement automatic execution of code as part of their application. This is implemented through two function called `BeginBlocker` and `EndBlocker`. They are called when the application receives respectively the `BeginBlock` and `EndBlock` messages from the Tendermint engine, which happens at the beginning and at the end of each block. The application must set the `BeginBlocker` and `EndBlocker` in its constructor via the [`SetBeginBlocker`](https://godoc.org/github.com/cosmos/cosmos-sdk/baseapp#BaseApp.SetBeginBlocker) and [`SetEndBlocker`](https://godoc.org/github.com/cosmos/cosmos-sdk/baseapp#BaseApp.SetEndBlocker) methods.
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In general, the `BeginBlocker` and `EndBlocker` functions are mostly composed of the `BeginBlock` and `EndBlock` functions of each of the application's modules. This is done by calling the `BeginBlock` and `EndBlock` functions of the module manager, which in turn will call the `BeginBLock` and `EndBlock` functions of each of the modules it contains. Note that the order in which the modules' `BegingBlock` and `EndBlock` functions must be called has to be set in the module manager using the `SetOrderBeginBlock` and `SetOrderEndBlock` methods respectively. This is done in the [application's constructor](#application-constructor), and the `SetOrderBeginBlock` and `SetOrderEndBlock` methods have to be called before the `SetBeginBlocker` and `SetEndBlocker` functions.
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As a sidenote, it is important to remember that application-specific blockchains are deterministic. Developers must be careful not to introduce non-determinism in `BeginBlocker` or `EndBlocker`, and must also be careful not to make them too computationally expensive, as [gas](./accounts-fees-gas.md/gas) does not constrain the cost of `BeginBlocker` and `EndBlocker` execution.
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As a sidenote, it is important to remember that application-specific blockchains are deterministic. Developers must be careful not to introduce non-determinism in `BeginBlocker` or `EndBlocker`, and must also be careful not to make them too computationally expensive, as gas does not constrain the cost of `BeginBlocker` and `EndBlocker` execution.
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You can see an example of `BeginBlocker` and `EndBlocker` functions [here](https://github.com/cosmos/gaia/blob/master/app/app.go#L224-L232).
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### Register Codec
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The `MakeCodec` function is the last important function of the `app.go` file. The goal of this function is to instantiate a codec `cdc` (e.g. [amino](./amino.md)) initiliaze the codec of the SDK and each of the application's modules using the `RegisterCodec` function.
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The `MakeCodec` function is the last important function of the `app.go` file. The goal of this function is to instantiate a codec `cdc` (e.g. amino) initialize the codec of the SDK and each of the application's modules using the `RegisterCodec` function.
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To register the application's modules, the `MakeCodec` function calls `RegisterCodec` on `ModuleBasics`. `ModuleBasics` is a [basic manager](./modules.md#basic-manager) which lists all of the application's modules. It is instanciated in the `init()` function, and only serves to easily register non-dependant elements of application's modules (such as codec). To learn more about the basic module manager, click [here](./modules.md#basic-manager).
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To register the application's modules, the `MakeCodec` function calls `RegisterCodec` on `ModuleBasics`. `ModuleBasics` is a basic manager which lists all of the application's modules. It is instantiated in the `init()` function, and only serves to easily register non-dependent elements of application's modules (such as codec). To learn more about the basic module manager,.
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You can see an example of a `MakeCodec` [here](https://github.com/cosmos/gaia/blob/master/app/app.go#L64-L70)
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## Modules
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Modules are the heart and soul of an SDK application. They can be considered as state-machines within the state-machine. When a transaction is relayed from the underlying Tendermint engine via the ABCI to the application, it is routed by `baseapp` to the appropriate module in order to be processed. This paradigm enables developers to easily build complex state-machines, as most of the modules they need often already exist. For developers, most of the work involved in building an SDK application revolves around building custom modules required by their application that do not exist, and integrating them with modules that do already exist into one coherent application. In the application directory, the standard practice is to store modules in the `x/` folder (not to be confused with the SDK's `x/` folder, which contains already-built modules).
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To learn more about modules, [click here](./modules.md)
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Modules are the heart and soul of an SDK application. They can be considered as state-machines within the state-machine. When a transaction is relayed from the underlying Tendermint engine via the ABCI to the application, it is routed by `baseapp` to the appropriate module in order to be processed. This paradigm enables developers to easily build complex state-machines, as most of the modules they need often already exist. For developers, most of the work involved in building an SDK application revolves around building custom modules required by their application that do not exist, and integrating them with modules that do already exist into one coherent application. In the application directory, the standard practice is to store modules in the `x/` folder (not to be confused with the SDK's `x/` folder, which contains already-built modules).
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### Application Module Interface
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Modules implement two interfaces defined in the Cosmos SDK, [`AppModuleBasic`](https://github.com/cosmos/cosmos-sdk/blob/master/types/module/module.go#L44-L57) and [`AppModule`](https://github.com/cosmos/cosmos-sdk/blob/master/types/module/module.go#L44-L57). The former implements basic non-dependant elements of the module, such as the `codec`, while the latter handles the bulk of the module methods (including methods that require references to other modules' `keeper`s). Both the `AppModule` and `AppModuleBasic` types are defined in a file called `./module.go`.
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Modules implement two interfaces defined in the Cosmos SDK, [`AppModuleBasic`](https://github.com/cosmos/cosmos-sdk/blob/master/types/module/module.go#L44-L57) and [`AppModule`](https://github.com/cosmos/cosmos-sdk/blob/master/types/module/module.go#L44-L57). The former implements basic non-dependant elements of the module, such as the `codec`, while the latter handles the bulk of the module methods (including methods that require references to other modules' `keeper`s). Both the `AppModule` and `AppModuleBasic` types are defined in a file called `./module.go`.
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`AppModule` exposes a collection of useful methods on the module that facilitates the composition of modules into a coherent application. Important methods include:
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- `Route()` and `QueryRoute()`: These methods the name of the route and querier route for the module, for [messages](#message-types) to be routed to the module's [`handler`](#handler) and queries to be routes to the module's [`querier`](#querier).
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- `NewHandler()` and `NewQuerierHandler()`: These methods return a `handler` and `querierHandler` respectively, in order to process a message or a query once they are routed.
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- `BeginBlock()`, `EndBlock()` and `InitGenesis()`: These methods are executed respectively at the beginning of each block, at the end of each block and at the start of the chain. They implement special logic the module requires to be triggered during those events. For example, the `EndBlock` function is frequently used by modules where voting occurs to tally the result of the votes.
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- `RegisterInvariants()`: This method registers the [invariants](./invariants.md) for the module. Invariants are checked at the end of every block to make sure no unpredicted behaviour is occuring.
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`AppModule`'s methods are called from the `module manager`(./modules.md#module-manager), which manages the application's collection of modules.
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To learn more about the application module interface, [click here](./modules.md#application-module-interface).
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- `NewHandler()` and `NewQuerierHandler()`: These methods return a `handler` and `querierHandler` respectively, in order to process a message or a query once they are routed.
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- `BeginBlock()`, `EndBlock()` and `InitGenesis()`: These methods are executed respectively at the beginning of each block, at the end of each block and at the start of the chain. They implement special logic the module requires to be triggered during those events. For example, the `EndBlock` function is frequently used by modules where voting occurs to tally the result of the votes.
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- `RegisterInvariants()`: This method registers the [invariants](./invariants.md) for the module. Invariants are checked at the end of every block to make sure no unpredicted behaviour is occuring.
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- `AppModule`'s methods are called from the `module manager`, which manages the application's collection of modules.
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### Message Types
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A message is a custom type defined by each module that implements the [`message`](https://github.com/cosmos/cosmos-sdk/blob/master/types/tx_msg.go#L8-L29) interface. Each `transaction` contains one or multiple `messages`. When a valid block of transactions is received by the full-node, Tendermint relays each one to the application via [`DeliverTx`](https://tendermint.com/docs/app-dev/abci-spec.html#delivertx). Then, the application handles the transaction:
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1. Upon receiving the transaction, the application first unmarshalls it from `[]bytes`.
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2. Then, it verifies a few things about the transaction like [fee payment and signatures](#accounts-fees-gas.md) before extracting the message(s) contained in the transaction.
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3. With the [`Type()`](https://github.com/cosmos/cosmos-sdk/blob/master/types/tx_msg.go#L16) method, `baseapp` is able to know which modules defines the message. It is then able to route it to the appropriate module's [handler](#handler) in order for the message to be processed.
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4. If the message is successfully processed, the state is updated.
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1. Upon receiving the transaction, the application first unmarshals it from `[]bytes`.
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2. Then, it verifies a few things about the transaction like [fee payment and signatures](#accounts-fees-gas.md) before extracting the message(s) contained in the transaction.
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3. With the [`Type()`](https://github.com/cosmos/cosmos-sdk/blob/master/types/tx_msg.go#L16) method, `baseapp` is able to know which modules defines the message. It is then able to route it to the appropriate module's [handler](#handler) in order for the message to be processed.
|
||||
4. If the message is successfully processed, the state is updated.
|
||||
|
||||
For a more detailed look at a transaction lifecycle, click [here](./tx-lifecycle.md).
|
||||
|
||||
Module developers create custom message types when they build their own module. The general practice is to prefix the type declaration of the message with `Msg`. For example, the message type [`MsgSend`](https://github.com/cosmos/cosmos-sdk/blob/master/x/bank/types/msgs.go#L10-L15) allows users to transfer tokens. It is processed by the handler of the `bank` module, which ultimately calls the `keeper` of the `auth` module in order to update the state.
|
||||
|
||||
To learn more about messages, [click here](./tx-msgs.md).
|
||||
|
||||
### Handler
|
||||
|
||||
The `handler` refers to the part of the module responsible for processing the message after it is routed by `baseapp`. `handler` functions of modules (except those of the `auth` module) are only executed if the transaction is relayed from Tendermint by the `DeliverTx` ABCI message. If the transaction is relayed by `CheckTx`, only stateless checks and fee-related (i.e. `auth` module-related) stateful checks are performed. To better understand the difference between `DeliverTx`and `CheckTx`, as well as the difference between stateful and stateless checks, click [here](./tx-lifecycle.md).
|
||||
|
||||
The handler of a module is generally defined in a file called `handler.go` and consists of:
|
||||
|
||||
- A **switch function** `NewHandler` to route the message to the appropriate handler function. This function returns a `handler` function, and is registered in the [`AppModule`](#application-module-interface) to be used in the application's module manager to initialize the [application's router](./baseapp.md#routing). See an example of such a switch [here](https://github.com/cosmos/sdk-application-tutorial/blob/master/x/nameservice/handler.go#L10-L22).
|
||||
- **One handler function for each message type defined by the module**. Developers write the message processing logic in these functions. This generally involves doing stateful checks to ensure the message is valid and calling [`keeper`](#keeper)'s methods to update the state.
|
||||
- A **switch function** `NewHandler` to route the message to the appropriate handler function. This function returns a `handler` function, and is registered in the [`AppModule`](#application-module-interface) to be used in the application's module manager to initialize the application's router. See an example of such a switch [here](https://github.com/cosmos/sdk-application-tutorial/blob/master/x/nameservice/handler.go#L10-L22).
|
||||
- **One handler function for each message type defined by the module**. Developers write the message processing logic in these functions. This generally involves doing stateful checks to ensure the message is valid and calling [`keeper`](#keeper)'s methods to update the state.
|
||||
|
||||
Handler functions return a result of type [`sdk.Result`](https://github.com/cosmos/cosmos-sdk/blob/master/types/result.go#L14-L37), which informs the application on whether the message was successfully processed.
|
||||
|
||||
To learn more about handlers, [click here](./handler.md).
|
||||
|
||||
### Keeper
|
||||
|
||||
`Keepers` are the gatekeepers of their module's store(s). To read or write in a module's store, it is mandatory to go through one of its `keeper`'s methods. This is ensured by the [object-capabilities](./ocap.md) model of the Cosmos SDK. Only objects that hold the key to a store can access it, and only the module's `keeper` should hold the key(s) to the module's store(s).
|
||||
|
||||
`Keepers` are generally defined in a file called `keeper.go`. It contains the `keeper`'s type definition and methods.
|
||||
`Keepers` are generally defined in a file called `keeper.go`. It contains the `keeper`'s type definition and methods.
|
||||
|
||||
The `keeper` type definition generally consists of:
|
||||
|
||||
- **Key(s)** to the module's store(s) in the multistore.
|
||||
- **Key(s)** to the module's store(s) in the multistore.
|
||||
- Reference to **other module's `keepers`**. Only needed if the `keeper` needs to access other module's store(s) (either to read or write from them).
|
||||
- A reference to the application's **codec**. The `keeper` needs it to marshal structs before storing them, or to unmarshal them when it retrieves them, because stores only accept `[]bytes` as value.
|
||||
- A reference to the application's **codec**. The `keeper` needs it to marshal structs before storing them, or to unmarshal them when it retrieves them, because stores only accept `[]bytes` as value.
|
||||
|
||||
Along with the type definition, the next important component of the `keeper.go` file is the `keeper`'s constructor function, `NewKeeper`. This function instantiates a new `keeper` of the type defined above, with a `codec`, store `keys` and potentially references to other modules' `keeper`s as parameters. The `NewKeeper` function is called from the [application's constructor](#constructor-function).
|
||||
Along with the type definition, the next important component of the `keeper.go` file is the `keeper`'s constructor function, `NewKeeper`. This function instantiates a new `keeper` of the type defined above, with a `codec`, store `keys` and potentially references to other modules' `keeper`s as parameters. The `NewKeeper` function is called from the [application's constructor](#constructor-function).
|
||||
|
||||
The rest of the file defines the `keeper`'s methods, primarily getters and setters. You can check an example of a `keeper` implementation [here](https://github.com/cosmos/sdk-application-tutorial/blob/master/x/nameservice/keeper.go).
|
||||
|
||||
To learn more about `keepers`, [click here](./keeper.md).
|
||||
### Querier
|
||||
|
||||
### Querier
|
||||
|
||||
`Queriers` are very similar to `handlers`, except they serve user queries to the state as opposed to processing transactions. A query is initiated from an [interface](#intefaces) by an end-user who provides a `queryRoute` and some `data`. The query is then routed to the correct application's `querier` by `baseapp`'s [`handleQueryCustom`](https://github.com/cosmos/cosmos-sdk/blob/master/baseapp/baseapp.go#L519-L556) method using `queryRoute`.
|
||||
`Queriers` are very similar to `handlers`, except they serve user queries to the state as opposed to processing transactions. A query is initiated from an [interface](#intefaces) by an end-user who provides a `queryRoute` and some `data`. The query is then routed to the correct application's `querier` by `baseapp`'s [`handleQueryCustom`](https://github.com/cosmos/cosmos-sdk/blob/master/baseapp/baseapp.go#L519-L556) method using `queryRoute`.
|
||||
|
||||
The `Querier` of a module is defined in a file called `querier.go`, and consists of:
|
||||
|
||||
- A **switch function** `NewQuerier` to route the query to the appropriate `querier` function. This function returns a `querier` function, and is is registered in the [`AppModule`](#application-module-interface) to be used in the application's module manager to initialize the [application's query router](./baseapp.md#query-routing). See an example of such a switch [here](https://github.com/cosmos/sdk-application-tutorial/blob/master/x/nameservice/querier.go#L21-L34).
|
||||
- - **One querier function for each data type defined by the module that needs to be queryable**. Developers write the query processing logic in these functions. This generally involves calling [`keeper`](#keeper)'s methods to query the state and marshalling it to JSON. See an example of `querier` functions [here](https://github.com/cosmos/sdk-application-tutorial/blob/master/x/nameservice/querier.go#L37-L101).
|
||||
|
||||
To learn more about `queriers`, [click here](./querier.md).
|
||||
- A **switch function** `NewQuerier` to route the query to the appropriate `querier` function. This function returns a `querier` function, and is is registered in the [`AppModule`](#application-module-interface) to be used in the application's module manager to initialize the application's query router. See an example of such a switch [here](https://github.com/cosmos/sdk-application-tutorial/blob/master/x/nameservice/querier.go#L21-L34).
|
||||
- - **One querier function for each data type defined by the module that needs to be queryable**. Developers write the query processing logic in these functions. This generally involves calling [`keeper`](#keeper)'s methods to query the state and marshaling it to JSON. See an example of `querier` functions [here](https://github.com/cosmos/sdk-application-tutorial/blob/master/x/nameservice/querier.go#L37-L101).
|
||||
|
||||
### Command-Line and REST Interfaces
|
||||
|
||||
Each module defines command-line commands and REST routes to be exposed to end-user via the [application's interfaces](#application-interfaces). This enables end-users to create messages of the types defined in the module, or to query the subset of the state managed by the module.
|
||||
Each module defines command-line commands and REST routes to be exposed to end-user via the [application's interfaces](#application-interfaces). This enables end-users to create messages of the types defined in the module, or to query the subset of the state managed by the module.
|
||||
|
||||
#### CLI
|
||||
|
||||
@@ -218,35 +204,29 @@ Generally, the commands related to a module are defined in a folder called `clie
|
||||
- Transactions commands let users generate new transactions so that they can be included in a block and eventually update the state. One command should be created for each [message type](#message-types) defined in the module. The command calls the constructor of the message with the parameters provided by the end-user, and wraps it into a transaction. The SDK handles signing and the addition of other transaction metadata. See examples of transactions commands [here](https://github.com/cosmos/sdk-application-tutorial/blob/master/x/nameservice/client/cli/tx.go).
|
||||
- Queries let users query the subset of the state defined by the module. Query commands forward queries to the [application's query router](./baseapp.md#query-routing), which routes them to the appropriate [querier](#querier) the `queryRoute` parameter supplied. See examples of query commands [here](https://github.com/cosmos/sdk-application-tutorial/blob/master/x/nameservice/client/cli/query.go).
|
||||
|
||||
To learn more about modules CLI, [click here](./module-interfaces.md#cli).
|
||||
|
||||
#### REST
|
||||
|
||||
The module's REST interface lets users generate transactions and query the state through REST calls to the application's [light client daemon](./node.md#lcd) (LCD). REST routes are defined in a file `client/rest/rest.go`, which is composed of:
|
||||
The module's REST interface lets users generate transactions and query the state through REST calls to the application's light client daemon (LCD). REST routes are defined in a file `client/rest/rest.go`, which is composed of:
|
||||
|
||||
- A `RegisterRoutes` function, which registers each route defined in the file. This function is called from the [main application's interface](#application-interfaces) for each module used within the application. The router used in the SDK is [Gorilla's mux](https://github.com/gorilla/mux).
|
||||
- Custom request type definitions for each query or transaction creation function that needs to be exposed. These custom request types build on the [base `request` type](https://github.com/cosmos/cosmos-sdk/blob/master/types/rest/rest.go#L32-L43) of the Cosmos SDK.
|
||||
- Custom request type definitions for each query or transaction creation function that needs to be exposed. These custom request types build on the [base `request` type](https://github.com/cosmos/cosmos-sdk/blob/master/types/rest/rest.go#L32-L43) of the Cosmos SDK.
|
||||
- One handler function for each request that can be routed to the given module. These functions implement the core logic necessary to serve the request.
|
||||
|
||||
See an example of a module's `rest.go` file [here](https://github.com/cosmos/sdk-application-tutorial/blob/master/x/nameservice/client/rest/rest.go).
|
||||
|
||||
To learn more about modules REST interface, [click here](./module-interfaces.md#rest).
|
||||
|
||||
## Application Interface
|
||||
|
||||
Interfaces let end-users interact with full-node clients. This means querying data from the full-node or creating and sending new transactions to be relayed by the full-node and eventually included in a block.
|
||||
Interfaces let end-users interact with full-node clients. This means querying data from the full-node or creating and sending new transactions to be relayed by the full-node and eventually included in a block.
|
||||
|
||||
The main interface is the [Command-Line Interface](./interfaces.md#cli). The CLI of an SDK application is built by aggregating [CLI commands](#cli) defined in each of the modules used by the application. The CLI of an application generally has the `-cli` suffix (e.g. `appcli`), and defined in a file called `cmd/appcli/main.go`. The file contains:
|
||||
The main interface is the Command-Line Interface. The CLI of an SDK application is built by aggregating [CLI commands](#cli) defined in each of the modules used by the application. The CLI of an application generally has the `-cli` suffix (e.g. `appcli`), and defined in a file called `cmd/appcli/main.go`. The file contains:
|
||||
|
||||
- **A `main()` function**, which is executed to build the `appcli` interface client. This function prepares each command and adds them to the `rootCmd` before building them. At the root of `appCli`, the function adds generic commands like `status`, `keys` and `config`, query commands, tx commands and `rest-server`.
|
||||
- **Query commands** are added by calling the `queryCmd` function, also defined in `appcli/main.go`. This function returns a Cobra command that contains the query commands defined in each of the application's modules (passed as an array of `sdk.ModuleClients` from the `main()` function), as well as some other lower level query commands such as block or validator queries. Query command are called by using the command `appcli query [query]` of the CLI.
|
||||
- **Transaction commands** are added by calling the `txCmd` function. Similar to `queryCmd`, the function returns a Cobra command that contains the tx commands defined in each of the application's modules, as well as lower level tx commands like transaction signing or broadcasting. Tx commands are called by using the command `appcli tx [tx]` of the CLI.
|
||||
- **A `registerRoutes` function**, which is called from the `main()` function when initializing the [application's light-client daemon (LCD)](./node.md#lcd) (i.e. `rest-server`). `registerRoutes` calls the `RegisterRoutes` function of each of the application's module, thereby registering the routes of the module to the lcd's router. The LCD can be started by running the following command `appcli rest-server`.
|
||||
- **Query commands** are added by calling the `queryCmd` function, also defined in `appcli/main.go`. This function returns a Cobra command that contains the query commands defined in each of the application's modules (passed as an array of `sdk.ModuleClients` from the `main()` function), as well as some other lower level query commands such as block or validator queries. Query command are called by using the command `appcli query [query]` of the CLI.
|
||||
- **Transaction commands** are added by calling the `txCmd` function. Similar to `queryCmd`, the function returns a Cobra command that contains the tx commands defined in each of the application's modules, as well as lower level tx commands like transaction signing or broadcasting. Tx commands are called by using the command `appcli tx [tx]` of the CLI.
|
||||
- **A `registerRoutes` function**, which is called from the `main()` function when initializing the [application's light-client daemon (LCD)](./node.md#lcd) (i.e. `rest-server`). `registerRoutes` calls the `RegisterRoutes` function of each of the application's module, thereby registering the routes of the module to the lcd's router. The LCD can be started by running the following command `appcli rest-server`.
|
||||
|
||||
See an example of an application's main command-line file [here](https://github.com/cosmos/sdk-application-tutorial/blob/master/cmd/nscli/main.go).
|
||||
|
||||
To learn more about interfaces, [click here](./interfaces.md).
|
||||
|
||||
## Dependencies and Makefile
|
||||
|
||||
This section is optional, as developers are free to choose their depencency manager and project building method. That said, the current most used framework for versioning control is [`go.mod`](https://github.com/golang/go/wiki/Modules). It ensures each of the libraries used throughout the application are imported with the correct version. An example can be found [here](https://github.com/cosmos/sdk-application-tutorial/blob/master/go.mod).
|
||||
|
||||
+43
-45
@@ -2,7 +2,7 @@
|
||||
|
||||
## Prerequisite Reading
|
||||
|
||||
* [Anatomy of an SDK Application](./app-anatomy.md)
|
||||
- [Anatomy of an SDK Application](./app-anatomy.md)
|
||||
|
||||
## Synopsis
|
||||
|
||||
@@ -26,16 +26,16 @@ One of the main application interfaces is the command-line interface. The transa
|
||||
|
||||
This command will automatically **create** the transaction, **sign** it using the account's private key, and **broadcast** it to the specified peer node.
|
||||
|
||||
There are several required and optional flags for transaction creation. The `--from` flag specifies which [account](./accounts-fees-gas.md#accounts) the transaction is orginating from. For example, if the transaction is sending coins, the funds will be drawn from the specified `from` address.
|
||||
There are several required and optional flags for transaction creation. The `--from` flag specifies which account the transaction is originating from. For example, if the transaction is sending coins, the funds will be drawn from the specified `from` address.
|
||||
|
||||
#### Gas and Fees
|
||||
|
||||
Additionally, there are several [flags](../interfaces/cli.md) users can use to indicate how much they are willing to pay in [fees](./accounts-fees-gas.md#fees):
|
||||
Additionally, there are several flags users can use to indicate how much they are willing to pay in fees:
|
||||
|
||||
* `--gas` refers to how much [gas](./accounts-fees-gas.md#gas), which represents computational resources, `Tx` consumes. Gas is dependent on the transaction and is not precisely calculated until execution, but can be estimated by providing `auto` as the value for `--gas`.
|
||||
* `--gas-adjustment` (optional) can be used to scale `gas` up in order to avoid underestimating. For example, users can specify their gas adjustment as 1.5 to use 1.5 times the estimated gas.
|
||||
* `--gas-prices` specifies how much the user is willing pay per unit of gas, which can be one or multiple denominations of tokens. For example, `--gas-prices=0.025uatom, 0.025upho` means the user is willing to pay 0.025uatom AND 0.025upho per unit of gas.
|
||||
* `--fees` specifies how much in fees the user is willing to pay in total.
|
||||
- `--gas` refers to how much gas, which represents computational resources, `Tx` consumes. Gas is dependent on the transaction and is not precisely calculated until execution, but can be estimated by providing `auto` as the value for `--gas`.
|
||||
- `--gas-adjustment` (optional) can be used to scale `gas` up in order to avoid underestimating. For example, users can specify their gas adjustment as 1.5 to use 1.5 times the estimated gas.
|
||||
- `--gas-prices` specifies how much the user is willing pay per unit of gas, which can be one or multiple denominations of tokens. For example, `--gas-prices=0.025uatom, 0.025upho` means the user is willing to pay 0.025uatom AND 0.025upho per unit of gas.
|
||||
- `--fees` specifies how much in fees the user is willing to pay in total.
|
||||
|
||||
The ultimate value of the fees paid is equal to the gas multiplied by the gas prices. In other words, `fees = ceil(gas * gasPrices)`. Thus, since fees can be calculated using gas prices and vice versa, the users specify only one of the two.
|
||||
|
||||
@@ -51,20 +51,19 @@ appcli tx send <recipientAddress> 1000uatom --from <senderAddress> --gas auto --
|
||||
|
||||
#### Other Transaction Creation Methods
|
||||
|
||||
The command-line is an easy way to interact with an application, but `Tx` can also be created using a [REST interface](../interfaces/rest.md) or some other entrypoint defined by the application developer. From the user's perspective, the interaction depends on the web interface or wallet they are using (e.g. creating `Tx` using [Lunie.io](https://lunie.io/#/) and signing it with a Ledger Nano S).
|
||||
The command-line is an easy way to interact with an application, but `Tx` can also be created using a REST interface or some other entrypoint defined by the application developer. From the user's perspective, the interaction depends on the web interface or wallet they are using (e.g. creating `Tx` using [Lunie.io](https://lunie.io/#/) and signing it with a Ledger Nano S).
|
||||
|
||||
## Addition to Mempool
|
||||
|
||||
Each full-node (running Tendermint) that receives `Tx` sends an [ABCI message](https://tendermint.com/docs/spec/abci/abci.html#messages), `CheckTx`, to the application layer to check for invalidity, and receives a Response. If `Tx` passes the checks, it is held in the nodes' [**Mempool**](https://tendermint.com/docs/tendermint-core/mempool.html#mempool)s (memory pools of transactions unique to each node) pending inclusion in a block - honest nodes will discard `Tx` if it is found to be invalid. Prior to consensus, nodes continuously check incoming transactions and gossip them to their peers.
|
||||
|
||||
|
||||
### Types of Checks
|
||||
|
||||
The full-nodes perform stateless, then stateful checks on `Tx` during `CheckTx`, with the goal to identify and reject an invalid transaction as early on as possible to avoid wasted computation.
|
||||
The full-nodes perform stateless, then stateful checks on `Tx` during `CheckTx`, with the goal to identify and reject an invalid transaction as early on as possible to avoid wasted computation.
|
||||
|
||||
***Stateless*** checks do not require nodes to access state - light clients or offline nodes can do them - and are thus less computationally expensive. Stateless checks include making sure addresses are not empty, enforcing nonnegative numbers, and other logic specified in the definitions.
|
||||
**_Stateless_** checks do not require nodes to access state - light clients or offline nodes can do them - and are thus less computationally expensive. Stateless checks include making sure addresses are not empty, enforcing nonnegative numbers, and other logic specified in the definitions.
|
||||
|
||||
***Stateful*** checks validate transactions and messages based on a committed state. Examples include checking that the relevant values exist and are able to be transacted with, the address has sufficient funds, and the sender is authorized or has the correct ownership to transact. At any given moment, full-nodes typically have [multiple versions](../core/baseapp.md#volatile-states) of the application's internal state for different purposes. For example, nodes will execute state changes while in the process of verifying transactions, but still need a copy of the last committed state in order to answer queries - they should not respond using state with uncommitted changes.
|
||||
**_Stateful_** checks validate transactions and messages based on a committed state. Examples include checking that the relevant values exist and are able to be transacted with, the address has sufficient funds, and the sender is authorized or has the correct ownership to transact. At any given moment, full-nodes typically have [multiple versions](../core/baseapp.md#volatile-states) of the application's internal state for different purposes. For example, nodes will execute state changes while in the process of verifying transactions, but still need a copy of the last committed state in order to answer queries - they should not respond using state with uncommitted changes.
|
||||
|
||||
In order to verify `Tx`, full-nodes call `CheckTx`, which includes both _stateless_ and _stateful_ checks. Further validation happens later in the [`DeliverTx`](#delivertx) stage. `CheckTx` goes through several steps, beginning with decoding `Tx`.
|
||||
|
||||
@@ -74,7 +73,7 @@ When `Tx` is received by the application from the underlying consensus engine (e
|
||||
|
||||
### ValidateBasic
|
||||
|
||||
[Messages](../core/tx-msgs.md#messages) are extracted from `Tx` and `ValidateBasic`, a function defined by the module developer for every message, is run for each one. It should include basic stateless sanity checks. For example, if the message is to send coins from one address to another, `ValidateBasic` likely checks for nonempty addresses and a nonnegative coin amount, but does not require knowledge of state such as account balance of an address.
|
||||
Messages are extracted from `Tx` and `ValidateBasic`, a function defined by the module developer for every message, is run for each one. It should include basic stateless sanity checks. For example, if the message is to send coins from one address to another, `ValidateBasic` likely checks for nonempty addresses and a nonnegative coin amount, but does not require knowledge of state such as account balance of an address.
|
||||
|
||||
### AnteHandler
|
||||
|
||||
@@ -84,7 +83,7 @@ For example, the [`auth`](https://github.com/cosmos/cosmos-sdk/tree/master/docs/
|
||||
|
||||
### Gas
|
||||
|
||||
The [`Context`](../core/context.md) used to keep track of important data while `AnteHandler` is executing `Tx` keeps a `GasMeter` which tracks how much gas has been used. The user-provided amount for gas is known as the value `GasWanted`. If `GasConsumed`, the amount of gas consumed so far, ever exceeds `GasWanted`, execution stops. Otherwise, `CheckTx` sets `GasUsed` equal to `GasConsumed` and returns it in the result. After calculating the gas and fee values, validator-nodes check that the user-specified `gas-prices` is less than their locally defined `min-gas-prices`.
|
||||
The `Context` used to keep track of important data while `AnteHandler` is executing `Tx` keeps a `GasMeter` which tracks how much gas has been used. The user-provided amount for gas is known as the value `GasWanted`. If `GasConsumed`, the amount of gas consumed so far, ever exceeds `GasWanted`, execution stops. Otherwise, `CheckTx` sets `GasUsed` equal to `GasConsumed` and returns it in the result. After calculating the gas and fee values, validator-nodes check that the user-specified `gas-prices` is less than their locally defined `min-gas-prices`.
|
||||
|
||||
### Discard or Addition to Mempool
|
||||
|
||||
@@ -105,39 +104,39 @@ The first step of consensus is the **block proposal**. One proposer amongst the
|
||||
The next step of consensus is to execute the transactions to fully validate them. All full-nodes that receive a block proposal execute the transactions by calling the ABCI functions [`BeginBlock`](./app-anatomy.md#beginblocker-and-endblocker), `DeliverTx` for each transaction, and [`EndBlock`](./app-anatomy.md#beginblocker-and-endblocker). While full-nodes each run everything individually, since the messages' state transitions are deterministic and transactions are explicitly ordered in the block proposal, this process yields a single, unambiguous result.
|
||||
|
||||
```
|
||||
-----------------------
|
||||
|Receive Block Proposal|
|
||||
-----------------------
|
||||
|
|
||||
-----------------------
|
||||
|Receive Block Proposal|
|
||||
-----------------------
|
||||
|
|
||||
v
|
||||
-----------------------
|
||||
| BeginBlock |
|
||||
-----------------------
|
||||
|
|
||||
v
|
||||
-----------------------
|
||||
| DeliverTx(tx0) |
|
||||
| DeliverTx(tx1) |
|
||||
| DeliverTx(tx2) |
|
||||
| DeliverTx(tx3) |
|
||||
| . |
|
||||
-----------------------
|
||||
| BeginBlock |
|
||||
-----------------------
|
||||
|
|
||||
v
|
||||
-----------------------
|
||||
| DeliverTx(tx0) |
|
||||
| DeliverTx(tx1) |
|
||||
| DeliverTx(tx2) |
|
||||
| DeliverTx(tx3) |
|
||||
| . |
|
||||
| . |
|
||||
| . |
|
||||
-----------------------
|
||||
|
|
||||
v
|
||||
-----------------------
|
||||
| EndBlock |
|
||||
|
|
||||
v
|
||||
-----------------------
|
||||
|
|
||||
v
|
||||
| EndBlock |
|
||||
-----------------------
|
||||
| Consensus |
|
||||
|
|
||||
v
|
||||
-----------------------
|
||||
|
|
||||
v
|
||||
| Consensus |
|
||||
-----------------------
|
||||
| Commit |
|
||||
|
|
||||
v
|
||||
-----------------------
|
||||
| Commit |
|
||||
-----------------------
|
||||
```
|
||||
|
||||
@@ -145,12 +144,11 @@ The next step of consensus is to execute the transactions to fully validate them
|
||||
|
||||
The `DeliverTx` ABCI function defined in [`baseapp`](../core/baseapp.md) does the bulk of the state change work: it is run for each transaction in the block in sequential order as committed to during consensus. Under the hood, `DeliverTx` is almost identical to `CheckTx` but calls the [`runTx`](../core/baseapp.md#runtx-and-runmsgs) function in deliver mode instead of check mode. Instead of using their `checkState` or `queryState`, full-nodes select a new copy, `deliverState`, to deliver `Tx`:
|
||||
|
||||
* **Decoding:** Since `DeliverTx` is an ABCI call, `Tx` is received in the encoded `[]byte` form. Nodes first unmarshal the transaction, then call `runTx` in `runTxModeDeliver`, which is very similar to `CheckTx` but also executes and writes state changes.
|
||||
* **Checks:** Full-nodes call `validateBasicMsgs` and the `AnteHandler` again. This second check happens because they may not have seen the same transactions during the Addition to Mempool stage and a malicious proposer may have included invalid ones. One difference here is that the `AnteHandler` will not compare `gas-prices` to the node's `min-gas-prices`since that value is local to each node - differing values across nodes would yield nondeterministic results.
|
||||
* **Route and Handler:** While `CheckTx` would have exited, `DeliverTx` continues to run [`runMsgs`](../core/baseapp.md#runtx-and-runmsgs) to fully execute each `Msg` within the transaction. Since the transaction may have messages from different modules, `baseapp` needs to know which module to find the appropriate Handler. Thus, the [`Route`](../core/tx-msgs.md#route)
|
||||
function is called to retrieve the route name and find the `Handler` within the module.
|
||||
* **Handler:** The `Handler`, a step up from `AnteHandler`, is responsible for executing each message's actions and causes state changes to persist in `deliverTxState`. It is defined within a `Msg`'s module and writes to the appropriate stores within the module.
|
||||
* **Gas:** While `Tx` is being delivered, a `GasMeter` is used to keep track of how much gas is left for each transaction; if execution completes, `GasUsed` is set and returned in the `Response`. If execution halts because `GasMeter` has run out or something else goes wrong, a deferred function at the end appropriately errors or panics.
|
||||
- **Decoding:** Since `DeliverTx` is an ABCI call, `Tx` is received in the encoded `[]byte` form. Nodes first unmarshal the transaction, then call `runTx` in `runTxModeDeliver`, which is very similar to `CheckTx` but also executes and writes state changes.
|
||||
- **Checks:** Full-nodes call `validateBasicMsgs` and the `AnteHandler` again. This second check happens because they may not have seen the same transactions during the Addition to Mempool stage and a malicious proposer may have included invalid ones. One difference here is that the `AnteHandler` will not compare `gas-prices` to the node's `min-gas-prices`since that value is local to each node - differing values across nodes would yield nondeterministic results.
|
||||
- **Route and Handler:** While `CheckTx` would have exited, `DeliverTx` continues to run [`runMsgs`](../core/baseapp.md#runtx-and-runmsgs) to fully execute each `Msg` within the transaction. Since the transaction may have messages from different modules, `baseapp` needs to know which module to find the appropriate Handler. Thus, the `Route` function is called to retrieve the route name and find the `Handler` within the module.
|
||||
- **Handler:** The `Handler`, a step up from `AnteHandler`, is responsible for executing each message's actions and causes state changes to persist in `deliverTxState`. It is defined within a `Msg`'s module and writes to the appropriate stores within the module.
|
||||
- **Gas:** While `Tx` is being delivered, a `GasMeter` is used to keep track of how much gas is left for each transaction; if execution completes, `GasUsed` is set and returned in the `Response`. If execution halts because `GasMeter` has run out or something else goes wrong, a deferred function at the end appropriately errors or panics.
|
||||
|
||||
If there are any failed state changes resulting from `Tx` being invalid or `GasMeter` running out, the transaction processing terminates and any state changes are reverted. Invalid transactions in a block proposal cause validator-nodes to reject the block and vote for a `nil` block instead. If `Tx` is delivered successfully, any leftover gas is returned to the user and the transaction is validated.
|
||||
|
||||
|
||||
Reference in New Issue
Block a user