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On May 11, an unknown issue on the Ethereum beacon chain caused transactions to halt for almost half an hour.
Around 8:15 pm on Thursday, May 11, a number of Ethereum core developers announced that Beacon Chain was having problems confirming transactions. New blocks could have been proposed, but an unknown problem kept them from being completed.
The beacon chain stopped finalizing about thirty minutes ago. I don’t know why yet, but in general the chain is designed to be resilient against this, transactions will continue as usual and finalization will kick in when the problem is resolved. pic.twitter.com/utAS0uAWpG
— superphiz.eth ️ (@superphiz) May 11, 2023
A similar issue arose on March 15, when low validator participation caused a delay in Goerli’s test run for the Ethereum “Shapella” upgrade, which was successfully completed on April 12.
Beacon Chain is the original Ethereum Proof-of-Stake blockchain, first launched in 2020. On September 15, 2022, the pre-existing Ethereum Proof-of-Work chain “merged” with Beacon Chain, completing the network’s transition to a faster and greener Proof-of-Stake consensus mechanism.
After 25 minutes, the mainnet began finalizing blocks again, with Ethereum core developer and Prysmatic Labs co-founder Preston Van Loon announcing that “finality has been restored.”
Finality has been restored. We do not know the root cause yet, but something happened to cause several client implementations to work really hard to keep up with the chain.
— prestonvanloon.eth (@preston_vanloon) May 11, 2023
According to blockchain analytics provider Beaconcha.in, between 200,552 and 200,554 Ethereum, there was a sharp and sudden decline in the number of attestations.
For context, an epoch is a period of 32 “slots” when validators propose and validate blocks. An epoch usually lasts about six minutes and 24 seconds.
The cause of the issue remains unclear, however, the Ethereum developers have stated that the issue is being investigated to prevent it from happening again.
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Following the incident, an Ethereum advisor going by the pseudonym @Superphiz noted that “client diversity” was one of the main reasons the loss of finality was so short-lived. However, he also pointed out that the loss of finality could have been avoided altogether if no single client had more than 33% control.
Client diversity refers to the number of software clients available to network validators, and more client diversity means a more secure and reliable network for validators.