How to properly set session keys for Relay and Parachain with custom keys

Question

The Goal:

Deploying a Relay Chain with Custom Validator Keys, that a Parachain can start collation successfully.

The Issue:

Using the key subcommand in the Relay, I wasn't able to properly insert the Session Keys to the Relay nodes' keystore.

The Relay with 2 validators was working fine, producing and finalizing blocks, but when I deployed a Parachain it outputted a WARN: collation wasn't advertised to any validator.

And it started to output the WARN for 5 minutes +- until it started to output an error. Finally I haven't found any mention whatsoever in how to do so.

Answer 1

The Solution:

After trying a lot of things, I've found from an RPC call that there's 7 keys needed for each Validator node. Those are, gran babe imon para asgn audi beef. And for each key-type there's a scheme, there's a table to reference.

Key-Type	Scheme
gran	ed25519
babe	sr25519
imon	sr25519
para	sr25519
asgn	sr25519
audi	sr25519
beef	ecdsa

Insert them like this,

./target/release/polkadot key insert \
--base-path <path for this validator> \
--chain <raw relay chainSpec> \
--scheme <see table> \
--suri "<mnemonic of this validator>" \
--key-type <see table>

Pay attention to the base-path you're choosing, you need separate paths for different validators. And to each path, you insert 7 keys using the same validators' private seed.

Parachain Session Keys:

In the Para, run the node and specify a RPC port to make a call later on.

./target/release/<parachain binary> --collator \
--force-authoring \
--chain <raw parachainSpec> \
--base-path /tmp/<para>/<path> \
--port 40333 \
--ws-port 8844 \
--rpc-port 9022 \
--unsafe-ws-external \
--rpc-methods=unsafe \
--rpc-external \
--rpc-cors=all \
-- \
--execution wasm \
--chain relay-raw.json \
--port 30343 \
--ws-port 9977 \
--bootnodes /ip4/<relay bootnode ip>/tcp/30333/p2p/<bootnode peerId>

Using this command as an example, the port open for RPC was 9022 so the insert key call should be:

curl -vH 'Content-Type: application/json' --data '{ "jsonrpc":"2.0", "method":"author_insertKey", "params":["aura", "<private seed in hex>", "<public key in hex>"],"id":1 }' http://127.0.0.1:9022

The private and public key here should be the collator keys. And it's for aura. So it is using the sr25519 scheme.

And it's output:

* Connection #0 to host 127.0.0.1 left intact
{"jsonrpc":"2.0","result":null,"id":1}

Answer 2

I think this warning is not related to the session keys. Try add more validators to the relaychain.

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And if you are using --alice or something like that. You don't need to insert the key manually. These are well-known keys.

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And if you want to insert your custom keys, check the runtime session keys configurations.

https://github.com/paritytech/cumulus/blob/220bc559f064d38485d5a21e2ba91a8a237e9d16/parachain-template/runtime/src/lib.rs#L168-L172

Let's take parachain-template as an example. As you can see from the link, you only need to insert the Aura key.