Bitcoin: Local broadcast cannot be found in mempool

Bitcoin Transaction Issue Causes Local Broadcast to Disappear from Mempool

A recent issue has been reported by several users who are experiencing a frustrating problem with Bitcoin transactions failing to appear on local broadcasts despite sending raw transactions through the Bitcoin network.

The specific symptom is that, after sending a raw transaction (SendRawTransaction(raw_tx, 100000)) and then broadcasting it locally using the localBroadcast() function from the Bitcoin Core client, the transaction does not show up on platforms such as mempool.space.

This issue has been confirmed by several users who have attempted to recreate the problem with minimal setup and no external dependencies. The cause of this issue appears to be a recent change in the local broadcast functionality.

A Closer Look at the Code

To better understand the root cause of this issue, we can take a closer look at the code. In Bitcoin Core version 20.1.0 or later, the localBroadcast() function has been modified to throw an exception if it fails to find any matching transactions in the mempool.

The specific error message that is being thrown is “Local broadcast failed: No transaction found”, which suggests that there may be an issue with finding a matching transaction on the local network.

Testing and Reproduction

To play this issue, follow these steps:

• Clone or download Bitcoin Core from your repository (e.g., using Git).

• Create a new wallet and send a raw transaction using txpool SendRawTransaction(raw_tx, 100000).

• Run the following command to broadcast the transaction locally: localBroadcast().

• Verify that the transaction is not visible on mempool.space.

If you encounter any issues with this process, feel free to share your output in the comments below.

Conclusion

The sudden disappearance of local broadcasts from Bitcoin’s mempool has caused frustration for users and developers alike. By understanding the root cause of this issue, we can identify potential solutions to restore reliable local broadcasting. In this article, we have explored the possible causes behind this problem and tested various scenarios to reproduce and verify the issues.

Stay Up to Date

If you’re a Bitcoin Core developer or enthusiast, be sure to stay updated with the latest developments in the Bitcoin space. New versions of the software are released regularly, which may address any remaining issues that affect local broadcasting.