Parachain collator cannot produce blocks after acquiring a Relaychian slot. (best block #0, cannot author the 1st block from gensis) It is getting some error below, parachain nodes fails to decode parent_head passed by Relaychain. https://github.com/paritytech/cumulus/blob/0c779d926beeb6e1f3f2aa777d9bcec792c0bdac/client/collator/src/lib.rs#L223

Debug log:

Jun 07 08:36:26 astar-alphanet-collator-node-0 astar-collator[64308]: 2022-06-07 08:36:26.675 ERROR tokio-runtime-worker cumulus-collator: [Parachain] Could not decode the head data. error=Error { cause: Some(Error { cause: Some(Error { cause: None, desc: "Could not decode `DigestItemType`, variant doesn't exist" }), desc: "Could not decode `Digest::logs`" }), desc: "Could not decode `Header::digest`" }
Jun 07 08:36:26 astar-alphanet-collator-node-0 astar-collator[64308]: 2022-06-07 08:36:26.675 DEBUG tokio-runtime-worker parachain::collation-generation: [Relaychain] collator returned no collation on collate para_id=2006

Could you teach me what could be the issue and how to avoid that?

Parachain: polkadot-0.9.19 Relaychain: westend based v0.9.23

Unlike this similar question (Parachain not producing blocks ? Error: Could not decode the head data), On-chain state of genesis-state (genesis head) & genesis-wasm (validationCode) properly starts with 0x.

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  • 2
    Have you created both genesis (state and wasm) using the same raw chain spec JSON file that your parachain is using to run? Maybe describing all the steps you took would be useful for us to help you. Jun 8, 2022 at 16:34
  • You try using a file upload ?
    – Nuke
    Jun 8, 2022 at 16:55
  • Also as a best practice, updating your Polkadot dependency should match on collator and relay chain. In this specific case I think you at incompatible. Try updating your coalitor
    – Nuke
    Jun 8, 2022 at 16:57
  • Thank you for your comments @ArturGontijo Yes, genesis state and wasm comes from the same raw chain spec JSON file. raw.githubusercontent.com/AstarNetwork/Astar/fix/… parachain-id is 2006 export-genesis-state & export-genesis-wasm result in the above state.
    – Shunsuke
    Jun 9, 2022 at 9:46
  • @DanShields I see. I'll try to update version
    – Shunsuke
    Jun 9, 2022 at 9:50

1 Answer 1


I'm really, sorry. The reason was chain-spec raw.json file had some wrong data. After recreating spec json, it started to produce blocks.

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