How can I start a Hydra Node in devnet?

Question

I have been researching on how to start a Hydra node in devnet using Docker and I found this link with these two simple commands:

docker pull ghcr.io/input-output-hk/hydra-node:latest
docker run --rm ghcr.io/input-output-hk/hydra-node --help

The problem is that, when I execute this, I get:

hydra-node - A prototype of Hydra Head protocol

Usage: hydra-node [-q|--quiet] [-n|--node-id INTEGER] [-h|--host IP] 
                  [-p|--port PORT] [-P|--peer ARG] [--api-host IP] 
                  [--api-port PORT] [--monitoring-port PORT] 
                  [--hydra-signing-key FILE] [--hydra-verification-key FILE] 
                  [--network-id INTEGER] [--node-socket FILE] 
                  [--cardano-signing-key FILE] [--cardano-verification-key FILE]
                  [--start-chain-from SLOT.HEADER_HASH] [--ledger-genesis FILE] 
                  [--ledger-protocol-parameters FILE] [--version] 
                  [--script-info]

  Starts a Hydra Node

Available options:
  -q,--quiet               Turns off any logging
  -n,--node-id INTEGER     Sets this node's id
  -h,--host IP             The address this node listens on for Hydra network
                           peers connection (default: 127.0.0.1)
  -p,--port PORT           The port this node listens on for Hydra network peers
                           connection (default: 5001)
  -P,--peer ARG            A peer address in the form <host>:<port>, where
                           <host> can be an IP address, or a host name
  --api-host IP            The address this node listens on for client API
                           connections (default: 127.0.0.1)
  --api-port PORT          The port this node listens on for client API
                           connections (default: 4001)
  --monitoring-port PORT   The port this node listens on for monitoring and
                           metrics. If left empty, monitoring server is not
                           started
  --hydra-signing-key FILE Our Hydra multisig signing key.
  --hydra-verification-key FILE
                           Other party multisig verification key.
  --network-id INTEGER     A test network with the given network magic.
  --node-socket FILE       Local (Unix) socket path to connect to cardano node.
  --cardano-signing-key FILE
                           Signing key for the internal wallet use for Chain
                           interactions.
  --cardano-verification-key FILE
                           Cardano verification key of other Hydra participant's
                           wallet.
  --start-chain-from SLOT.HEADER_HASH
                           The point at which to start on-chain component.
                           Defaults to chain tip at startup time.
  --ledger-genesis FILE    Path to a Shelley-compatible genesis JSON file.
  --ledger-protocol-parameters FILE
                           Path to a JSON file describing protocol parameters
                           (same format as returned from 'cardano-cli query
                           protocol-parameters')
  -h,--help                Show this help text
  --version                Show version
  --script-info            Dump script info as JSON

This doesn't seem to start anything.

What is the correct way to start hydra-node?

Answer 1

Here you can find the official documentation on Hydra.

There is also a demo section where it is explained how to use it

Answer 2

You are running with the --help option: 'docker run --rm ghcr.io/input-output-hk/hydra-node --help'

This will only ever show you the help information.

Answer 3

This is how you run hydra-node in Devnet. You need to have Docker installed.

Keep in mind that, at the moment, this is just a POC:

1. git clone https://github.com/input-output-hk/hydra-poc
2. cd hydra-poc/demo/
3. ./prepare-devnet.sh
4. ./run-docker.sh

This will start 1 instance of cardano-node and 3 instances of hydra-node.

If you open a new terminal, you can check they are working correctly with this command (you need to be in the hydra-poc/demo directory):

docker-compose ps

Once this is done, you can check the initial state of the network using this command:

docker-compose exec cardano-node cardano-cli query utxo --testnet-magic 42 --whole-utxo

You can also send some ada to Alice, Bob and Carol addresses using:

./seed-devnet.sh

Now, if you check the status of the network again, you'll see something like this:

                           TxHash                                 TxIx        Amount
--------------------------------------------------------------------------------------
0ad134cc87cdf66a6863464b4393501eda7632f7c268b068c48b2aaf84f20e51     1        250000000 lovelace + TxOutDatumNone
2e80d483600acf194661e89bb08aee0cbb2844cf237e43d5e949d11038db9a96     1        100000000 lovelace + TxOutDatumHash ScriptDataInAlonzoEra "a654fb60d21c1fed48db2c320aa6df9737ec0204c0ba53b9b94a09fb40e757f3"
3eeea5c2376b033d5bdeab6fe551950883b04c08a37848c6d648ea03476dce83     1        1000000000 lovelace + TxOutDatumNone
648d71c1cbd835f6e1966c06ba0ad4347c3b399ef00576e59aee18b9e1ec9489     0        897949001186 lovelace + TxOutDatumNone
648d71c1cbd835f6e1966c06ba0ad4347c3b399ef00576e59aee18b9e1ec9489     1        100000000 lovelace + TxOutDatumHash ScriptDataInAlonzoEra "a654fb60d21c1fed48db2c320aa6df9737ec0204c0ba53b9b94a09fb40e757f3"
6db235b8759454654d19baf3ef601a2cb0e4ea3ebdc5e9db466dd07bccf53c7d     1        500000000 lovelace + TxOutDatumNone
94f16fc2a16b7ffa96c7929cbfc1e2f05424b6508612d4513fa23eaf458dc14b     1        100000000 lovelace + TxOutDatumHash ScriptDataInAlonzoEra "a654fb60d21c1fed48db2c320aa6df9737ec0204c0ba53b9b94a09fb40e757f3"

If at any point you'll like to restart the docker containers, I suggest you run the following:

docker-compose stop
docker-compose rm -f

Then you'll be able to do ./run-docker.sh again.

There's also a client which you can use to play a little with the Hydra heads:

docker-compose --profile tui run hydra-tui-1

You can change between hydra-tui-1, hydra-tui-2 and hydra-tui-3, depending on which hydra-node you want to connect with. Only when you close a head you'll see the changes committed to the main chain (cardano-node).