# Rosetta

The rosetta package implements Coinbase's Rosetta API (opens new window). This document provides instructions on how to use the Rosetta API integration. For information about the motivation and design choices, refer to ADR 035.

# Add Rosetta Command

The Rosetta API server is a stand-alone server that connects to a node of a chain developed with Cosmos SDK.

To enable Rosetta API support, it's required to add the RosettaCommand to your application's root command file (e.g. appd/cmd/root.go).

Import the server package:

Copy "github.com/cosmos/cosmos-sdk/server"

Find the following line:

Copy initRootCmd(rootCmd, encodingConfig)

After that line, add the following:

Copy rootCmd.AddCommand( server.RosettaCommand(encodingConfig.InterfaceRegistry, encodingConfig.Marshaler) )

The RosettaCommand function builds the rosetta root command and is defined in the server package within Cosmos SDK.

Since we’ve updated the Cosmos SDK to work with the Rosetta API, updating the application's root command file is all you need to do.

An implementation example can be found in simapp package.

# Use Rosetta Command

To run Rosetta in your application CLI, use the following command:

Copy appd rosetta --help

To test and run Rosetta API endpoints for applications that are running and exposed, use the following command:

Copy appd rosetta --blockchain "your application name (ex: gaia)" --network "your chain identifier (ex: testnet-1)" --tendermint "tendermint endpoint (ex: localhost:26657)" --grpc "gRPC endpoint (ex: localhost:9090)" --addr "rosetta binding address (ex: :8080)"

# Extensions

There are two ways in which you can customize and extend the implementation with your custom settings.

# Message extension

In order to make an sdk.Msg understandable by rosetta the only thing which is required is adding the methods to your messages that satisfy the rosetta.Msg interface. Examples on how to do so can be found in the staking types such as MsgDelegate, or in bank types such as MsgSend.

# Client interface override

In case more customization is required, it's possible to embed the Client type and override the methods which require customizations.

Example:

Copy package custom_client import ( "context" "github.com/coinbase/rosetta-sdk-go/types" "github.com/cosmos/cosmos-sdk/server/rosetta/lib" ) // CustomClient embeds the standard cosmos client // which means that it implements the cosmos-rosetta-gateway Client // interface while at the same time allowing to customize certain methods type CustomClient struct { *rosetta.Client } func (c *CustomClient) ConstructionPayload(_ context.Context, request *types.ConstructionPayloadsRequest) (resp *types.ConstructionPayloadsResponse, err error) { // provide custom signature bytes panic("implement me") }

NOTE: when using a customized client, the command cannot be used as the constructors required may differ, so it's required to create a new one. We intend to provide a way to init a customized client without writing extra code in the future.

# Error extension

Since rosetta requires to provide 'returned' errors to network options. In order to declare a new rosetta error, we use the errors package in cosmos-rosetta-gateway.

Example:

Copy package custom_errors import crgerrs "github.com/cosmos/cosmos-sdk/server/rosetta/lib/errors" var customErrRetriable = true var CustomError = crgerrs.RegisterError(100, "custom message", customErrRetriable, "description")

Note: errors must be registered before cosmos-rosetta-gateway's Server.Start method is called. Otherwise the registration will be ignored. Errors with same code will be ignored too.