Investigate zombienet-polkadot-functional-0003-beefy-and-mmr test failure

[serban300]

https://gitlab.parity.io/parity/mirrors/polkadot-sdk/-/jobs/6059252

[serban300]

Ran it a lot of times locally and it didn't reproduce. Also doesn't seem to reproduce in the CI. I will close the issue for the moment.

[serban300]

I have an idea about what might have caused the failure:

Copying the error here in case the zombienet log is deleted

2024-04-25 13:33:18        API/INIT: rococo/1010000: Not decorating unknown runtime apis: 0x6ff52ee858e6c5bd/1, 0xfbc577b9d747efd6/1
2024-04-25 13:33:18        RPC-CORE: verifyProofStateless(root: MmrHash, proof: MmrLeafBatchProof): bool:: 8013: Invalid proof: Error::Verify
 Error running script: ./0003-mmr-generate-and-verify-proof.js 	 8013: Invalid proof: Error::Verify

The test code:

async function run(nodeName, networkInfo, nodeNames) {
  const apis = await common.getApis(networkInfo, nodeNames);

  const proof = await apis[nodeName].rpc.mmr.generateProof([1, 9, 20]);

  const root = await apis[nodeName].rpc.mmr.root()

  const proofVerifications = await Promise.all(
    Object.values(apis).map(async (api) => {
      return api.rpc.mmr.verifyProof(proof);
    })
  );

  const proofVerificationsStateless = await Promise.all(
    Object.values(apis).map(async (api) => {
      return api.rpc.mmr.verifyProofStateless(root, proof);
    })
  );

  // check that all nodes accepted the proof
  return proofVerifications.every((proofVerification) => proofVerification) && proofVerificationsStateless.every((proofVerification) => proofVerification)
}

If a new block is generated between these 2 lines:

  const proof = await apis[nodeName].rpc.mmr.generateProof([1, 9, 20]);

  const root = await apis[nodeName].rpc.mmr.root()

we will try to verify a proof for the previous block with the mmr root at the current block. Which will fail.