Layer 2 blockchain Arbitrum briefly stopped processing transactions on Wednesday due to a bug in its sequencer bringing the ecosystem, which has $2.21 billion in total value locked, to a halt.
Arbitrum’s sequencer takes user transactions, bundles them together and posts them on-chain. A bug occurred at the point where transactions were expected to be posted on-chain. This resulted in the transactions being reverted and a delay to network operations.
“Impact: A temporary pause to finalize transaction ordering on-chain, but otherwise the Sequencer’s service was not disrupted,” said Arbitrum’s developers on Twitter.
The developers pushed back on claims that the sequencer had run out of funds and said the “system was tested and worked as intended.” However, they did not provide details on the glitch and said a full post-mortem would be posted in due course.
DL News reported that on-chain data shows that the sequencer used up its stock of ether to pay for transactions and therefore they couldn’t be processed. However, Arbitrum developers said this is a deliberate fail-safe mechanism.
The sequencer uses two wallets, including the main sequencer wallet that has a relatively low ether balance and gets automatically refilled by a second wallet known as the “gas-refunder” wallet, which has a high ether balance.
The gas-refunder wallet refills the sequencer wallet when batches are processed successfully, the developers said. However, they added that if there is a malfunction in the sequencer then it won’t be refilled or refunded. DL News reported that a wallet appeared to manually top up the sequencer’s gas fees enabling transactions to start processing again.
“The Arbitrum network did not refund the Sequencer for this malfunction nor was it caused by the Sequencer running out of funds,” said the developers, adding that the fail-safe mechanism worked as intended.
Arbitrum is now processing transactions again. The network’s token ARB is down 3.4% over the last 24 hours, according to data from Coingecko.