Continuing our adventures in setting up a private beacon chain… Previously we got an Eth 1 chain with the deposit contract and successfully sent a deposit to register a new validator. So far though, we have no way of telling if it actually worked. What we need is an actual beacon chain client. Enter Artemis…

Step 3 – Add a Beacon Chain Client

We’ll be using Artemis, partly because I’m incredibly biased and partly because it happens to support the exact version of the deposit contract we’ve deployed (what a coincidence!).

We’ll need a config file for it, the vast majority of which is boiler plate I copied and probably don’t actually need. The important bit though is we need to point it at our Pantheon node so it can query the ETH1 chain data. We also need to tell it the address of our deposit contract:

[deposit]
# normal, test, simulation
# "test" pre-production
# "simulation" to run a simulation of deposits with ganache-cli, if a inputFile is included the file will replay the deposits
# "normal" production, must include contractAddr and nodeUrl
mode = "normal"
...
contractAddr = "0xdddddddddddddddddddddddddddddddddddddddd"
nodeUrl = "http://eth1:8545"

Note that “eth1” is the name we gave to our Pantheon docker image. Docker will do its magic to resolve that to Pantheon’s IP address inside the container.

And then we have some relatively standard docker boiler plate in our run.sh script for it.

If you’ve followed all the steps from part 1 and actually sent a deposit transaction, when you run Artemis after a few moments it should create a JSON file in artemis/output/artemis.json containing something like:

{
  "amount": 32000000000,
  "eventType": "Deposit",
  "merkle_tree_index": "0",
  "pubkey": "0x88526BB3800ABB7BA3E4DF4255D043AA661EDDBBFDC0B8C3209034B7EEA65EB3C32AAF0E5D19E8998A1CE5E2B9B64299",
  "withdrawal_credentials": "0x008098BD37974616EC6DA256B5D2650E2363D011B7CEF902F7CCBFE938CBA0EA"
}

Which is a record indicating it has received and recognised our deposit. Pretty much nothing else happens though because we still don’t have enough validators to actually get the beacon chain started. I suspect running some 65,000 validators on my laptop might be a little ambitious so the next step is likely to be tweaking config to reduce the number of validators required before the chain starts.