A parachain in Rococo is missing more block slots than I would expect it to at fairly random times.

Version: Polkadot v0.9.42 Number of Collators: 3

Logging: (Perhaps I am missing the correct trace log to see the issue?)

-lcumulus-collator=trace \
-laura=trace \
-laura::cumulus=trace \
-lcumulus-consensus-relay-chain=trace \
-lsc_basic_authorship::basic_authorship=trace \

Perhaps most useful part of the log:

cumulus-collator: [Parachain] Producing candidate relay_parent=0x04baa2159d77d3557a3d6ac6088f37874b714b2a2c3df609dbbe9b36c1b437d6
cumulus-collator: [Parachain] Starting collation. relay_parent=0x04baa2159d77d3557a3d6ac6088f37874b714b2a2c3df609dbbe9b36c1b437d6 at=0x1e9acf648cfd7d37aecd93b7bca2a09e6ad56e9f28a1d762c223b2228897650a
aura: [Parachain] Checking log DigestItem::PreRuntime(...)
aura: [Parachain] Checking log DigestItem::Seal(...)
aura: [Parachain] Ignoring digest not meant for us
aura: [Parachain] No block for 2 slots. Applying exponential lenience, total proposing duration: 750ms
aura: [Parachain] Starting authorship at slot: 140922534
sc_basic_authorship::basic_authorship: [Parachain] 🙌 Starting consensus session on top of parent 0x1e9acf648cfd7d37aecd93b7bca2a09e6ad56e9f28a1d762c223b2228897650a
sc_basic_authorship::basic_authorship: [Parachain] Attempting to push transactions from the pool.
sc_basic_authorship::basic_authorship: [Parachain] Pool status: PoolStatus { ready: 0, ready_bytes: 0, future: 0, future_bytes: 0 }
sc_basic_authorship::basic_authorship: [Parachain] 🎁 Prepared block for proposing at 1680005 (0 ms) [hash: 0x53252500318ec20bc6d8ad20269819d623c83b804063bcdde94d5e3ce0cd5967; parent_hash: 0x1e9a…650a; extrinsics (2): [0xb875…d7bb, 0xc288…4d21]]
aura: [Parachain] 🔖 Pre-sealed block for proposal at 1680005. Hash now 0x88fb38e98a275c9b78a04902c48d6d59fea3949731c43855406f62fccb5809cb, previously 0x53252500318ec20bc6d8ad20269819d623c83b804063bcdde94d5e3ce0cd5967.
substrate: [Parachain] ✨ Imported #1680005 (0x88fb…09cb)

Full Log in Gist: https://gist.github.com/wilwade/f4ec02bc60a6863c0a1fed66957f8aae

Appearance: Looks like the collators are forming the candidate blocks, but the candidate blocks are not getting included in the relay chain.

Things I don't think it is:

  1. Appears that the collator is forming the blocks at the right time and on top of the correct relay parent (Not a relay chain sync issue)
  2. No failing transactions on the Relay chain blocks (that I can see)
  3. Not a sync issue between the collators
  4. No invalid transactions as these are "empty" blocks
  5. Rococo Relay appears to be happy
  6. Lots of debug logs that would indicate specific errors are not showing up. Too many to list.
  7. Not a block finalization issue

So actual questions:

  1. aura: [Parachain] No block for n slots This appears to just be telling me what I already know, that no blocks were formed when we expected them to be. Is that a correct interpretation of the log? (Log is inside of https://paritytech.github.io/substrate/master/sc_consensus_slots/fn.proposing_remaining_duration.html)
  2. There are some Relay chain Reorgs, but I don't think those are causing the issue.
  3. Other ideas of things to log?
  4. Other ideas?
  • Anything happened before this error appears? migration, another issue with a collator...
    – Alex Bean
    Aug 4, 2023 at 7:44
  • Another idea to check is this previous SE: substrate.stackexchange.com/questions/6724/… it might be a transaction in the pool that is slowing it down
    – Alex Bean
    Aug 4, 2023 at 7:45
  • No transactions or migrations. No appearances of issues with other collators. I hit the issue again last night, and I can see 🎁 Prepared block for proposing at 1683906 13 times across two collators (logs on the third are harder to get). They keep trying and eventually it gets through. Always getting Pool status: PoolStatus { ready: 0, ready_bytes: 0, future: 0, future_bytes: 0 } so no tx failing as far as I can tell. All the collators appear happy from a load perspective as well.
    – Wil W
    Aug 4, 2023 at 12:30
  • Can you open an issue in Cumulus with all the details and link your issue here as well?
    – Bruno
    Aug 4, 2023 at 20:24
  • Issue submitted: github.com/paritytech/cumulus/issues/2976 Also added a more recent log of the setup in case it is helpful: gist.github.com/wilwade/aa1f4ea8dace5938aa8e7a430b780eb1
    – Wil W
    Aug 7, 2023 at 12:36


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Browse other questions tagged or ask your own question.