Relayer fails to submit transaction due to dust change output (200 < 546 satoshis)

[Stakecraft]

While using a Torram node with a relayer, I encountered an error when attempting to submit a transaction to testnet3. The relayer tries to create a transaction where the change output is 200 satoshis, which is below the dust threshold of 546 satoshis, causing the transaction to be rejected with the error "change would be dust: 200 < 546 satoshis".

Logs

2025-03-25T07:52:14.043782Z error Failed to process and submit batch {"error": "failed to submit to blockchain: change would be dust: 200 < 546 satoshis", "attempt": 6, "max_retries": 50}
2025-03-25T07:52:14.043821Z info Retrying after backoff {"backoff_duration": 60, "attempt": 6}
...

Issue Description

• The relayer selects a UTXO with an amount of 1200 satoshis (1.2e-05 BTC).
• After constructing the transaction, the change output is 200 satoshis, which is below the dust threshold (546 satoshis) for a P2PKH output.
• Bitcoin Core rejects the transaction, as this is standard behavior for dust outputs.
• The relayer continues to retry sending the transaction (up to 50 attempts) instead of adjusting it or reporting the error and stopping.

Expected Behavior

• The relayer should check the dust threshold before submitting a transaction.
• If the change is below 546 satoshis, the relayer should:
  • Either not create a change output and add the remainder to the fee.
  • Or select another UTXO to ensure the change is above the threshold.
  • Or report the error and stop retrying.
• The error message should be more informative for users.

Suggestion

• Add a check for the dust threshold in the relayer's logic.
• Add a configuration option for the minimum change amount.
• Improve the error message to be more user-friendly.

Environment

• Torram node (version: 1.0).
• Bitcoin Core 28.1.0.
• Network: testnet3.
• OS: Ubuntu 22.04