Blockchain Emergency Release

The 2020.09.16.0 emergency release addresses the chain halt we observed after activating PoC-v9. The team will continue to closely monitor the situation but we're fairly confident that this update will get the blockchain moving again.

Contents

With every chain variable update there's a little uncertainty that older code paths may get broken. The team tries their best to test any such changes thoroughly but sometimes bugs slip through the cracks.

What exactly happened?

• We believe that the root cause of the chain halt was the fact that we were re-validating poc_receipts_txn by using a lagging ledger while trying to absorb the transaction. We have addressed that by getting the required channel information for witnesses by walking the chain backwards instead of relying on a potentially old ledger.

• Furthermore, rewards_txn were being extremely expensive due to unnecessary logging, thereby causing IO issues. We have reduced the log levels from info to debug to address that.

Related PRs

• • Fix poc eunits and reduce log level
  • blockchain-core/619
• • Dont call check_is_valid_poc to get channels*
  • blockchain-core/621

Plan

Since this is an emergency release, we have already began betaing it on some hotspots and will be deploying it throughout the network around 5:30PM PST, Wednesday 16th Sept.