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Optimize block connection logging using LazyTxid #4659

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Optimize block connection logging using LazyTxid #4659

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3f9be17
channelmanager: improve block connection logging
kamal-ogtl May 2, 2026
06d752d
Address review feedback: defer double-SHA256 computations in debug lo…
kamal-ogtl May 3, 2026
3453b75
Merge branch 'lightningdevkit:main' into block-connection-logging
kamal-ogtl Jun 4, 2026
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11 changes: 10 additions & 1 deletion lightning/src/ln/channelmanager.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -16191,6 +16191,15 @@ impl<

let block_hash = header.block_hash();
log_trace!(self.logger, "{} transactions included in block {} at height {} provided", txdata.len(), block_hash, height);
struct LazyTxid<'a>(&'a Transaction);

@TheBlueMatt TheBlueMatt Jun 8, 2026

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I don't see what this is actually doing?

impl<'a> core::fmt::Display for LazyTxid<'a> {
fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {
write!(f, "{}", self.0.compute_txid())
}
}
for (_, tx) in txdata.iter() {
log_debug!(self.logger, "Confirmed transaction {} in block {} at height {}", LazyTxid(tx), block_hash, height);

@TheBlueMatt TheBlueMatt Jun 8, 2026

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No, we really don't want to log every txid in the block - we have no idea if the transactions are event relevant to us at this point, and the list may well contain every single transaction in the block.

}
Comment on lines +16200 to +16202

@ldk-claude-review-bot ldk-claude-review-bot Jun 4, 2026

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This loop logs every transaction in txdata, but txdata is not necessarily filtered to only channel-relevant transactions. In the Listen::block_connected → filtered_block_connected → transactions_confirmed path, txdata contains all transactions in the block (see block_connected default impl in chain/mod.rs:190-192). Even with BIP 157/158 compact block filters, the filtering is block-level, not transaction-level, so a matching block still delivers all its transactions here.

On mainnet blocks with ~2000-3000 transactions, this produces thousands of DEBUG log lines per block (~every 10 minutes), almost all for transactions completely unrelated to the node's channels. If DEBUG is enabled, each line also triggers a compute_txid() (double-SHA256 of the serialized transaction).

Consider either:

  1. Moving this logging after channel processing so you only log transactions that actually triggered a channel update, or
  2. Gating this on TRACE instead of DEBUG, consistent with the existing aggregate log on the line above.


let _persistence_guard =
PersistenceNotifierGuard::optionally_notify_skipping_background_events(
Expand Down Expand Up @@ -16222,7 +16231,7 @@ impl<
// See the docs for `ChannelManagerReadArgs` for more.

let block_hash = header.block_hash();
log_trace!(self.logger, "New best block: {} at height {}", block_hash, height);
log_info!(self.logger, "New best block: {} at height {}", block_hash, height);

let _persistence_guard =
PersistenceNotifierGuard::optionally_notify_skipping_background_events(
Expand Down
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