# Tutorial: Running a Relay Server for Fun and Profit
Users that rely on GSNv2 to access distributed applications (dapps) need to access relays through the Internet to get their messages to the blockchain. While any user can access any relay to communicate with any dapp, it is expected that dapp developers will contribute back to GSNv2 by running a relay or two. Also, if you buy and hold ether as an investment you might as well run a relay and earn a bit extra (see explanation)
In this article you learn how to run a relay on a cloud VM using Google Cloud Platform Compute (opens new window), though your can use any other hosting provider.
# Relays as an investment
Relays get reimbursed by paymasters for the gas they spend sending transactions for users, plus a transaction fee that you can configure.
Without significant transaction volume you won't necessarily get a super impressive interest rate, but you will get paid to support decentralization while taking little to no risk. Minimal resources are required to run a relay server so your costs will be low. For example, GCP does not charge you for running a single micro instance (opens new window).
When you want to get your ETH back you use the same account you used to register the relay to unstake (deregister) it. After the unstake period, which is about a week, you can request all your locked funds.
# Setting your relay server's transaction fee
When you configure the
gsn-relay-config.json file later, you will see two variables,
For every transaction you relay you can expect to earn
pctRelayFee% of the cost of the gas for the transaction (in addition to being
reimbursed for gas used).
The client code selects relays based on price. If your fees are too high, you will not get anything. Click here to see what other relay servers are charging (opens new window).
# The Relay VM
# Initial Setup
First you need to set up the virtual machine (VM) that will run the relay server.
Click CREATE INSTANCE.
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 Container Deploy a container image to this VM instance Selected Container image * (it does not matter, you just need to type something) Firewall Allow HTTPS traffic Selected Firewall Allow HTTP traffic Selected
Configure the external IP of the relay in the DNS. 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 relay VM.
- On a computer that is authorized to ssh into the relay VM,
download the relay configuration setup and
put it on the relay VM:
curl https://raw.githubusercontent.com/opengsn/gsn/master/dockers/relaydc/rdc > rdc chmod +x rdc ./rdc <relay VM name> addalias yes
- Open SSH to the relay VM.
- Download the relay configuration files.
curl https://raw.githubusercontent.com/opengsn/gsn/master/dockers/relaydc/.env > .env mkdir config curl https://raw.githubusercontent.com/opengsn/gsn/master/dockers/relaydc/config-sample/gsn-relay-config.json > config/gsn-relay-config.json
Parameter Value HOST Your host name
- Press Ctrl-O and then Enter to save the modified file.
- Press Ctrl-X to exit.
Parameter Value HOST Your host name baseRelayFee The base fee that your relay will charge pctRelayFee The percent fee that your relay will charge versionRegistryAddress The address for the version registry on the network you are using. See this list. 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://
- Download and run the docker images
rdc config rdc up -d
- Wait until the second
- To see the progress of the HTTPS server (the slowest component to set up), run
rdc logs -f https-portal
- When you see this line it means the setup is done. You can close the SSH window.
[services.d](https-portal_1 | ) done.
- Browse to https://<your DNS name>/gsn1/getaddr .
You should receive a JSON file with addresses and status.
readysetting should be
false, because it isn't registered with the relay hub yet.
# Relay Staking and Registration
We need to register the relay with the Relay Hub. This has several purposes:
- Stake one ether on the relay's honesty, so relays won't try to abuse the system (for example by submitting invalid messages)
- Put up the initial relay budget for sending messages. The default is 2 Ether.
- Add the relay to the relay list so clients will know they can use it for free messages
You can use any UNIX computer for this process, but it requires the mnemonic, the twelve word pass phrase for your account. This is an extremely sensitive piece of information, which you never want away from your control.
- Install the GSN command line interface on Docker. It has to be the Docker version
to be able to specify the gas price for the registration transaction.
sudo docker image pull opengsn/cli
- Create a file
pass12with the twelve word mnemonic for the account you'll use to fund the relay.
- Get the current gas price for transactions from here (opens new window). The low cost should be sufficient
- Register the relay. You may get an error saying that after 60 seconds the relay
is not yet ready. If so, ignore it, it is usually just because it takes a bit
docker run --rm -ti -v $PWD:$PWD \ opengsn/cli relayer-register \ --network <the ethereumNodeURL you used for the relay> \ --gasPrice <get from the link above, specify in Gwei> \ --relayUrl https://<your hostname for the relay>/gsn1 \ -m `pwd`/pass12
To avoid risking your main account, you can create a dedicated address (opens new window) and transfer 3.001 ether to it. One ether is the stake that you lose if your relay doesn't relay messages honestly, two ethers are the initial funds for the relay, and the 0.001 is for the gas needed for the registration itself. Make sure to keep the mnemonic, you need will it at some point to unstake the relay and get back your ether (and some extra).
- Browse to https://<your DNS name>/gsn1/getaddr . See that the relay is now ready. Congratulations.
Eventually you will want the ether back. To do so:
- Go here (opens new window) with your wallet (for example, MetaMask) set to the account that created the relay in the first place.
- Enter your
RelayManagerAddress(from https://<your DNS name>/getaddr) and click Unlock your stake.
- To see the block in which you'll be able to get back your stake either open the browser's console or
run this command on the relay. Either way, look for
docker logs default_gsn1_1 2>1 | grep withdrawBlock
- Use https://<network name>.etherscan.io to see the latest block, wait until it is past the withdrawal block.
- Go back to the unstake page (opens new window) and enter
- Click Withdraw previously unlocked stake.
In this article you learned how to create a GSNv2 relay and connect it to the network. The more relays are available, the better the performance for users who rely on GSNv2 to access dapps without spending ether.
Original version of this tutorial by Ori Pomerantz firstname.lastname@example.org