Bitcoin QT failed to write block / Dogecoin hashrate wallet

Multiple versions of the bitcoin client began failing this week, after a rogue transaction stopped users from restarting the software.

“Just opened my laptop and started Bitcoin QT and received the message blockchain corrupt, I clicked OK and now it appears “Reindexing blocks – 204 weeks, ” said the poster. “Also, my Bitcoins are Unconfirmed. What happened, why the message?”

Others quickly reported the same error on multiple computers, running different versions of Bitcoin-QT, which is the standard graphical user interface (GUI)-enabled version of the bitcoin client. Reindexing the blocks using the bitcoin client failed to solve the problem. The same problem affected Bitcoind, which is the non-GUI-based version of the client.

The problem was a result of a bug originally introduced in version 0.8.0 of the bitcoin client, which was first released in February. That version was a major release, which switched the database used to store the block chain from Berkeley DB to LevelDB, to solve a security problem.

“It is a bug in our code that checks for LevelDB database inconsistencies introduced when we switched to LevelDB storage in the 0.8.0 release, combined with a bug that checks the version number in transactions, ” said Gavin Andresen, chief developer. “A transaction with a bad version number triggered the problem.”

Gregory Maxwell, another member of the core developer team, posted a workaround for the problem yesterday morning. He explained to CoinDesk that since 0.8.0, the software has stored transactions with negative version numbers incorrectly in the local version of the block chain.

“This incorrect behaviour is, by itself, harmless and until yesterday there had not been any transactions with a negative version.”

However, on Monday, such a transaction was released, and stored in the client. Because the software enforces a rigorous database consistency check that runs whenever it is started, it refused to start after these transactions were included in the chain, he said.

Neither Andresen or Maxwell said that they had seen any evidence of significant network disruption. Andresen pointed out that it doesn’t affect the biggest, critical pieces of network infrastructure such as mining pools, merchants, or exchanges, because they tend to keep their bitcoin software running, usually with multiple nodes.