Summary
TLDR: Polygon’s zkEVM rollup entered an emergency state after a sequencer failure caused by a reorg on the Ethereum mainnet. This led to processing errors and a 14-hour downtime, affecting around 4,000 transactions. The emergency state was deactivated after an upgrade was pushed through. Centralization issues were highlighted, but improvements are expected over time. The network’s Security Council approved the emergency state, and the chain is working on adding support for EIP-4844 in the future.
Key Points
1. Polygon’s zkEVM rollup entered an emergency state on March 23 after the chain stopped processing blocks. Last week, Polygon released an analysis of the outage that took its zkEVM down.
2. Polygon reported late Saturday that its zkEVM sequencer had failed, attributing the cause to a reorg of the Ethereum mainnet. The postmortem states that the synchronizer for Polygon zkEVM mishandled the reorg, and the chain started processing batches of transactions with incorrect timestamps.
3. A blockchain reorganization, or reorg, happens when a network discards blocks from a previous version and adopts a new chain of blocks as the accurate history of transactions. This can occur when different parts of the network temporarily disagree on recent transaction order or validity. The network eventually converges on a single version of the truth, choosing the chain of blocks with the most computational work (or, in some consensus mechanisms, the most stake backing it) as the correct sequence. Reorgs help to ensure that the network remains secure and consistent, though it can lead to temporary uncertainties in transaction histories.