The election failed. No new era is planned

Question

I set up the private network of 8/10, everything is working fine, all the validators validate the blocks but after the an era I am facing an issue that the staking.StakingElectionFailed. The election failed. No new era is planned. I don't know how to fix this. I followed this link https://github.com/polkadot-js/apps/issues/7607#issuecomment-1129752912 and also followed other link to purge the chain but still facing this issue that the era time is not completing. I have many scenario in which I am facing the same issue of era completion 8/10 private network is one of them.

After this I again the setup the private network of 10/10 and this time everything is working fine but i want to know that why there is era time completion issue when i setup the 8/10 private network

Answer 1

Why

Check the PolkadotJS algorithm.

info.currentIndex.sub(activeEraStartSessionIndex).imul(info.sessionLength).iadd(sessionProgress);

Due to the election failure. ErasStartSessionIndex won't be updated. So, the PolkadotApps get a ridiculously big number.

You could check your log:

journalctl -u darwinia-node.service | grep "election provider failed"
Sep 08 06:32:18 pangoro-g1 drml[136952]: 2022-09-08 06:32:18 [14058] 💸 election provider failed due to ElectionError::Fallback("NoFallback.")

I guess you encounter the same error as me.

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The easiest way to fix

To solve this, you just need to change the Fallback to frame_election_provider_support::onchain::OnChainSequentialPhragmen<Runtime>. I guess you have set it to NoFallback before.

Because your validator set is pretty small, on-chain computation is totally fine.

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Debug & other fixes

Check the logs in feasibility_check to find out what's the root cause.

You need to know that once you enter the emergency mode with NoFallback, that is a dead loop.

You've to do one of these to recover the election:

• force set CurrentPhase with root
• calculate the result with offchain tool then submit it through set_emergency_election_result
• change NoFallback to OnChainSequentialPhragmen