Tutorial: Running a Relay Server for Fun and Profit

Introduction

Users that rely on the GSN to access distributed applications (dapps) need to access relays through the Internet to get their messages to the blockchain. Any user can access any relay to communicate with any supported dapp. If you are a dapp developer you can participate in the GSN by running a relay themselves and making it a preferred relay. You can run a Relay Server only to earn from relaying transaction fees.

This article explains how to run a relayer on a cloud VM using Google Cloud Platform Compute (opens new window), though your can use any other hosting provider.

Running a Relay Server For Profit

Relay Servers get reimbursed by Paymasters for the gas they spend sending transactions for users, plus a transaction fee that is defined by the network.

Profits of a Relay Server vary based on transaction volume, but there is little risk involved in running a Relay Server. Minimal resources are required to run a Relay Server. For example, GCP does not charge you for running a single micro instance (opens new window).

When you want to get your stake back you use the same account you used to register the relayer to unstake and deregister it. After the unstake period, which is about a week, you can withdraw all your locked funds.

Directions

Requirements

• The Relay Server Virtual Machine with docker installed, with a publicly accessible static IP address.
• A DNS service (such as GoDaddy, NameCheap, or DuckDNS) to give your host a DNS name.
• Enough Ether to activate and fund the Relay Server.
• For technical assistance, please use our discord channel (opens new window)

The Relay Server Virtual Machine

Initial Setup

First you need to set up the virtual machine (VM) that will run the relay server.

1. Go to the GCP console (opens new window).

2. Click CREATE INSTANCE.

3. Set these parameters (you can accept the default for all the others):

   Heading	Parameter	Value
   Name		Select a meaningful name
   Machine configuration	Machine type	e2-micro
   Boot disk	Container Optimized OS	Selected
   Firewall	Allow HTTPS traffic	Selected
   Firewall	Allow HTTP traffic	Selected

4. Click Create.

5. Obtain a DNS entry for a registrar service. Some major DNS services are: Namecheap (opens new window), GoDaddy (opens new window), or even a free service, such as DuckDNS (opens new window)

6. Configure the external IP of the relay in the DNS by adding an "A" record for that IP your DNS service. Note: by default, public IP is "ephemeral" and might change after reboot.

The Docker Container

Now that the VM is running and has a DNS entry, the next step is to actually run the relay software. It runs inside a docker container. You configure it using a script called rdc, which needs to run with more permissions than the GCP container-optimized OS (opens new window) allows. So you need to run it from a different computer that is authorized to SSH into the relayer VM.

Note

If you don't have this permission restriction, you can also download the script directly on the vm, and run the following commands using the "local" option.

1. Open SSH to the relayer VM.
2. Download the relayer configuration files.

The docker-compose.yml file must be placed at the home folder. The gsn-relay-config.json must be placed inside a config folder.

curl https://raw.githubusercontent.com/opengsn/gsn/master/dockers/docker-compose.yml > docker-compose.yml
mkdir config
curl https://raw.githubusercontent.com/opengsn/gsn/master/dockers/config-sample/gsn-relay-config.json > config/gsn-relay-config.json

1. Press Ctrl-O and then Enter to save the modified file.

2. Press Ctrl-X to exit.

3. Edit config/gsn-relay-config.json to specify:

   Parameter	Value
   relayHubAddress	The address for the RelayHub on the network you are using. See this list.
   managerStakeTokenAddress	The address for the ERC-20 token used for stake on the network you are using. See this list.
   ownerAddress	The owner account that will be used by relayer-register, below
   ethereumNodeUrl	The URL to a node on the network you wish to use. If you do not know what to put here, get a free Infura account (opens new window), create a project, and look at KEYS > ENDPOINTS for your network. Use the endpoint that starts with https://

4. Put the following values in a .env file:

   Variable	Example value	Comment
   HOST	my.hostname.com	Your Relay Server URL exactly as it is accessed by GSN Clients
   DEFAULT_EMAIL	me@hostname.com	Your e-mail for LetsEncrypt to send SSL alerts to

5. Download and run the docker images

   docker-compose up
   

   Note: if there is no 'docker-compose' alias installed on your cloud instance, run it as following:

   docker run --rm -v /var/run/docker.sock:/var/run/docker.sock -v "$PWD:$PWD" -w="$PWD" docker/compose:1.27.3 up
   

6. To see the progress of the HTTPS server (the slowest component to set up), get the id of the "https-portal" container and run:

   docker ps
   docker logs <https-portal container-id>
   

7. When you see this line it means the setup is done. You can close the SSH window.

   [services.d](https-portal_1  | ) done.
   

8. Browse to https://<your-DNS-name>/getaddr/ You should receive a JSON file with addresses and status. The ready setting should be false, because it isn't registered with the relay hub yet.

You can also check the activity of the relayer when you are on the vm. Get the id of the "jsrelay" container.

docker ps
docker logs <jsrelay container-id>

Relayer Staking and Registration

We need to register the relayer with the Relay Hub. This step has several purposes:

• Stake Ether or any supported ERC-20 token on the relay's honesty, so relays won't try to abuse the system (for example by submitting invalid messages)
• Fund the relayer with the initial account balance for sending transactions. The default is 2 Ether.
• Add the relayer to the on-chain relayers list so clients will know they can use it for free messages

You will need to make transactions from an account specified as ownerAddress in the Relay Server configuration. Make sure you have this account selected in MetaMask for the following steps.

1. Go to https://relays.opengsn.org/ and click "Register New Relay".
2. Enter your Relay Server URL and click "Register".
3. Follow the steps on the Relay Registration page.
4. Open https://<your-DNS-name>/getaddr/ . See that the relayer is now ready. Congratulations.

Note

In order to test your relayer, add its URL to the list of preferedRelays for your client's RelayProvider. Otherwise, your client is free to pick any active relay.

WARNING

The relayer generates its own Ethereum keystores & addresses internally. Do not tamper with the files or use these addresses to any other purpose. The relayer is staked on the network, performing other actions may result in penalization and loss of funds.