cosmos-sdk/docs/interfaces/rest.md

REST Interface

Prerequisites {hide}

• Query Lifecycle {prereq}
• Application CLI {prereq}

Application REST Interface

Building the REST Interface for an application is done by aggregating REST Routes defined in the application's modules. This interface is served by a REST Server REST server, which route requests and output responses in the application itself. The SDK comes with its own REST Server by default. To enable it, the rest.ServeCommand command needs to be added as a subcommand of the rootCmd in the main() function of the CLI interface:

rootCmd.AddCommand(rest.ServeCommand(cdc, registerRoutes))

Users will then be able to use the application CLI to start a new REST server, a local server through which they can securely interact with the application without downloading the entire state. The command entered by users would look something like this:

appcli rest-server --chain-id <chainID> --trust-node

Note that if trust-node is set to false, the REST server will verify the query proof against the merkle root (contained in the block header).

REST Server

A REST Server is used to receive and route HTTP Requests, obtain the results from the application, and return a response to the user. The REST Server defined by the SDK rest package contains the following:

• Router: A router for HTTP requests. A new router can be instantiated for an application and used to match routes based on path, request method, headers, etc. The SDK uses the Gorilla Mux Router.
• CLIContext: A CLIContext created for a user interaction.
• Keybase: A Keybase is a key manager.
• Logger: A logger from Tendermint Log, a log package structured around key-value pairs that allows logging level to be set differently for different keys. The logger takes Debug(), Info(), and Error()s.
• Listener: A listener from the net package.

Of the five, the only attribute that application developers need interact with is the router: they need to add routes to it so that the REST server can properly handle queries. See the next section for more information on registering routes.

In order to enable the REST Server in an SDK application, the rest.ServeCommand needs to be added to the application's command-line interface. See the above section for more information.

Registering Routes

To include routes for each module in an application, the CLI must have some kind of function to register routes in its REST Server. This function is called RegisterRoutes(), and is utilized by the ServeCommand and must include routes for each of the application's modules. Since each module used by an SDK application implements a RegisterRESTRoutes function, application developers simply use the Module Manager to call this function for each module (this is done in the application's constructor).

At the bare minimum, a RegisterRoutes() function should use the SDK client package RegisterRoutes() function to be able to route RPC calls, and instruct the application Module Manager to call RegisterRESTRoutes() for all of its modules. This is done in the main.go file of the CLI (typically located in ./cmd/appcli/main.go).

func registerRoutes(rs *rest.RestServer) {
	client.RegisterRoutes(rs.CliCtx, rs.Mux)
	app.ModuleBasics.RegisterRESTRoutes(rs.CliCtx, rs.Mux)
}

This function is specific to the application and passed in to the ServeCommand, which should be added to the rootCmd as such:

rootCmd.AddCommand(rest.ServeCommand(cdc, registerRoutes))