Set up your relayer

Configuration

The relayer is responsible for watching for new messages on the origin chain(s) and delivering them to their destination chains. This involves being able to submit transactions to many destination chains, and therefore requires access to a key for signing transactions. There are two supported key types: hexadecimal private keys (for in-memory signing), and AWS KMS based keys (best practice for production environments).

Hexadecimal keys

A hexadecimal private key used for in-memory signing can be used by your relayer to sign transactions. This is the recommended setup for testing or development purposes.

AWS KMS keys

An AWS KMS key can be used by your relayer to sign transactions. This is the recommended setup for production relayers.

See the Agent Keys page to set up your Hexadecimal or AWS KMS keys

Reference

Also take a look at the agent configuration page and the configuration reference for a full list of configuration possibilities. The list below is not complete, however it should be enough to get started.

Your relayer takes as configuration the following:

Argument	Description
--relayChains	Comma separated names of the origin and destination chains to relay messages between. Example: ethereum,polygon,avalanche(Also see config-reference for how to specify origin and destination chains independently)
--chains.[chain_name].connection.url	An RPC url for chain_name. Example: --chains.ethereum.connection.url='http://localhost:8545' Relayers must set multiple connection URLs, one for each chain it interacts with.
--whitelist	An optional whitelist. The relayer will only relay messages that match this whitelist. See message-filtering for more info.
--blacklist	An optional blacklist. The relayer will not relay messages that match this blacklist. See message-filtering for more info.
--db	The path to where the validator should write persistent data to disk. Ensure this path to be persistent when using cloud setups. When using Docker, make sure to mount the persistent path/volume into the container.See config-reference for more info
--allowLocalCheckpointSyncers	If true, this will allow the relayer to look for validator signatures on the relayer's local filesystem. In a production environment, this should be false. If you're running a validator on the same machine by following the validator local setup instructions, set this to true so that your relayer can access the local validator signatures.

Environment variable	Description
CONFIG_FILES	If you want to add additional configuration files you can add additional paths here as a comma separated list. These files must be accessible within the filesystem your agent has access to. If you're running in Docker, see the docker section of agent configuration for tips on mounting your config files into your Docker container.

Setup-specific configuration

These configurations requirements differ depending on which setup instructions you followed.

Hexidecimal Key

If you created a hexadecimal key, use these configs.

Argument	Description
--defaultSigner.key	A hexadecimal private key used to sign transactions for all chains. Example: --defaultSigner.key=123...def

AWS KMS Key

If you created an AWS KMS key, use these configs.

Argument	Description
--defaultSigner.type	Set to aws. Example: --defaultSigner.type=aws
--defaultSigner.id	The alias of your validator's AWS KMS key, prefixed with alias/. Example: --defaultSigner.id=alias/hyperlane-validator-signer-polygon
--defaultSigner.region	The region of your AWS KMS key. --defaultSigner.region=us-east-1

Environment variable	Description
AWS_ACCESS_KEY_ID	The access key ID of your relayer's AWS IAM user.
AWS_SECRET_ACCESS_KEY	The secret access key of your relayer's AWS IAM user.

For chain-specific signers take a look at the configuration reference

Installation

The recommended installation method for a production environment is using a Docker image.

Docker image

To download the docker image, run:

docker pull gcr.io/abacus-labs-dev/hyperlane-agent:3b1b8dc-20231115-202111

Building from source

First, clone the repo

git clone git@github.com:hyperlane-xyz/hyperlane-monorepo.git

And then follow the setup instructions in the rust directory

Start Relaying

Running the binary

Refer to the installation instructions to access the relayer binary. Configuration can be placed in a relayer.env file, for example:

# These are example values to roughly illustrate
# what a .env file should look like

HYP_BASE_RELAYCHAINS=ethereum,polygon,avalanche
HYP_BASE_DB="/hyperlane_db"
# ...
# ...

To run the relayer binary with the environment variables specified in relayer.env:

Using Docker

Find the latest docker image and set it to the environment variable $DOCKER_IMAGE.

Using the --env-file flag, we can pass in the environment variables to the relayer:

docker run \
  -it \
  --env-file relayer.env \
  --mount type=bind,source="$(pwd)"/hyperlane_db,target=/hyperlane_db \
  $DOCKER_IMAGE \
  ./relayer

info

If you have followed the instructions to deploy hyperlane and are specifying a path to your own config file in the CONFIG_FILES environment variable, check out the config files with docker section of agent configuration.

tip

If you're running validators with a local setup on the same machine and want the relayer to access these validator signatures, be sure to mount your local validator's signature directory into your relayer at the same path that you used when announcing your validator

For example, if your local validator is writing signatures to /tmp/hyperlane-validator-signatures-ethereum, you should mount a directory for the Docker container:

docker run \
  -it \
  --env-file relayer.env \
  --mount type=bind,source="$(pwd)"/hyperlane-validator-signatures-ethereum,target=/tmp/hyperlane-validator-signatures-ethereum,readonly \
  --mount type=bind,source="$(pwd)"/hyperlane_db,target=/hyperlane_db \
  $DOCKER_IMAGE \
  ./relayer

Building from source

See these instructions for building from source without Docker.

We can run the built binary from within the hyperlane-monorepo/rust directory with the environment variables found in relayer.env:

env $(cat relayer.env | grep -v "#" | xargs) ./target/release/relayer

Relayers needs to index all historic messages for the origin chain(s). This information is stored in a local database on disk (set with db in the config). This means running a relayer for the first time may take some extra time to catch up with the current state.