forked from cerc-io/ipld-eth-server
147 lines
8.0 KiB
Markdown
147 lines
8.0 KiB
Markdown
# composeAndExecute
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The `composeAndExecute` command is used to compose and execute over an arbitrary set of custom transformers.
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This is accomplished by generating a Go pluggin which allows the `vulcanizedb` binary to link to external transformers, so
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long as they abide by one of the standard [interfaces](../staging/libraries/shared/transformer).
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This command requires Go 1.11+ and [Go plugins](https://golang.org/pkg/plugin/) only work on Unix-based systems.
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## Writing custom transformers
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Storage Transformers
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* [Guide](../../staging/libraries/shared/factories/storage/README.md)
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* [Example](../../staging/libraries/shared/factories/storage/EXAMPLE.md)
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Event Transformers
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* [Guide](../../staging/libraries/shared/factories/event/README.md)
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* [Example](https://github.com/vulcanize/ens_transformers)
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## Preparing transformers to work as a plugin for composeAndExecute
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To plug in an external transformer we need to:
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1. Create a package that exports a variable `TransformerInitializer`, `StorageTransformerInitializer`, or `ContractTransformerInitializer` that are of type [TransformerInitializer](../staging/libraries/shared/transformer/event_transformer.go#L33)
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or [StorageTransformerInitializer](../../staging/libraries/shared/transformer/storage_transformer.go#L31),
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or [ContractTransformerInitializer](../../staging/libraries/shared/transformer/contract_transformer.go#L31), respectively
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2. Design the transformers to work in the context of their [event](../staging/libraries/shared/watcher/event_watcher.go#L83),
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[storage](../../staging/libraries/shared/watcher/storage_watcher.go#L53),
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or [contract](../../staging/libraries/shared/watcher/contract_watcher.go#L68) watcher execution modes
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3. Create db migrations to run against vulcanizeDB so that we can store the transformer output
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* Do not `goose fix` the transformer migrations
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* Specify migration locations for each transformer in the config with the `exporter.transformer.migrations` fields
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* If the base vDB migrations occupy this path as well, they need to be in their `goose fix`ed form
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as they are [here](../../staging/db/migrations)
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To update a plugin repository with changes to the core vulcanizedb repository, replace the vulcanizedb vendored in the plugin repo (`plugin_repo/vendor/github.com/vulcanize/vulcanizedb`)
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with the newly updated version
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* The entire vendor lib within the vendored vulcanizedb needs to be deleted (`plugin_repo/vendor/github.com/vulcanize/vulcanizedb/vendor`)
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* These complications arise due to this [conflict](https://github.com/golang/go/issues/20481) between `dep` and Go plugins
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## Configuration
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A .toml config file is specified when executing the command:
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`./vulcanizedb composeAndExecute --config=./environments/config_name.toml`
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The config provides information for composing a set of transformers:
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```toml
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[database]
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name = "vulcanize_public"
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hostname = "localhost"
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user = "vulcanize"
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password = "vulcanize"
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port = 5432
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[client]
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ipcPath = "/Users/user/Library/Ethereum/geth.ipc"
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[exporter]
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home = "github.com/vulcanize/vulcanizedb"
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name = "exampleTransformerExporter"
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save = false
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transformerNames = [
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"transformer1",
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"transformer2",
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"transformer3",
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"transformer4",
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]
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[exporter.transformer1]
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path = "path/to/transformer1"
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type = "eth_event"
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repository = "github.com/account/repo"
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migrations = "db/migrations"
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rank = "0"
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[exporter.transformer2]
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path = "path/to/transformer2"
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type = "eth_contract"
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repository = "github.com/account/repo"
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migrations = "db/migrations"
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rank = "0"
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[exporter.transformer3]
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path = "path/to/transformer3"
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type = "eth_event"
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repository = "github.com/account/repo"
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migrations = "db/migrations"
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rank = "0"
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[exporter.transformer4]
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path = "path/to/transformer4"
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type = "eth_storage"
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repository = "github.com/account2/repo2"
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migrations = "to/db/migrations"
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rank = "1"
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```
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- `home` is the name of the package you are building the plugin for, in most cases this is github.com/vulcanize/vulcanizedb
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- `name` is the name used for the plugin files (.so and .go)
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- `save` indicates whether or not the user wants to save the .go file instead of removing it after .so compilation. Sometimes useful for debugging/trouble-shooting purposes.
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- `transformerNames` is the list of the names of the transformers we are composing together, so we know how to access their submaps in the exporter map
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- `exporter.<transformerName>`s are the sub-mappings containing config info for the transformers
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- `repository` is the path for the repository which contains the transformer and its `TransformerInitializer`
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- `path` is the relative path from `repository` to the transformer's `TransformerInitializer` directory (initializer package).
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- Transformer repositories need to be cloned into the user's $GOPATH (`go get`)
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- `type` is the type of the transformer; indicating which type of watcher it works with (for now, there are only two options: `eth_event` and `eth_storage`)
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- `eth_storage` indicates the transformer works with the [storage watcher](../../staging/libraries/shared/watcher/storage_watcher.go)
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that fetches state and storage diffs from an ETH node (instead of, for example, from IPFS)
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- `eth_event` indicates the transformer works with the [event watcher](../../staging/libraries/shared/watcher/event_watcher.go)
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that fetches event logs from an ETH node
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- `eth_contract` indicates the transformer works with the [contract watcher](../staging/libraries/shared/watcher/contract_watcher.go)
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that is made to work with [contract_watcher pkg](../../staging/pkg/contract_watcher)
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based transformers which work with either a light or full sync vDB to watch events and poll public methods ([example1](https://github.com/vulcanize/account_transformers/tree/master/transformers/account/light), [example2](https://github.com/vulcanize/ens_transformers/tree/working/transformers/domain_records))
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- `migrations` is the relative path from `repository` to the db migrations directory for the transformer
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- `rank` determines the order that migrations are ran, with lower ranked migrations running first
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- this is to help isolate any potential conflicts between transformer migrations
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- start at "0"
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- use strings
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- don't leave gaps
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- transformers with identical migrations/migration paths should share the same rank
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- Note: If any of the imported transformers need additional config variables those need to be included as well
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This information is used to write and build a Go plugin which exports the configured transformers.
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These transformers are loaded onto their specified watchers and executed.
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Transformers of different types can be run together in the same command using a single config file or in separate instances using different config files
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The general structure of a plugin .go file, and what we would see built with the above config is shown below
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```go
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package main
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import (
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interface1 "github.com/vulcanize/vulcanizedb/libraries/shared/transformer"
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transformer1 "github.com/account/repo/path/to/transformer1"
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transformer2 "github.com/account/repo/path/to/transformer2"
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transformer3 "github.com/account/repo/path/to/transformer3"
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transformer4 "github.com/account2/repo2/path/to/transformer4"
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)
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type exporter string
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var Exporter exporter
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func (e exporter) Export() []interface1.EventTransformerInitializer, []interface1.StorageTransformerInitializer, []interface1.ContractTransformerInitializer {
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return []interface1.TransformerInitializer{
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transformer1.TransformerInitializer,
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transformer3.TransformerInitializer,
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}, []interface1.StorageTransformerInitializer{
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transformer4.StorageTransformerInitializer,
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}, []interface1.ContractTransformerInitializer{
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transformer2.TransformerInitializer,
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}
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}
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```
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