lightningd: don't loop through all commands every time one finishes.
What the developer wrote
Authored by Rusty Russell
lightningd: don't loop through all commands every time one finishes.
When we have many commands, this is where we spend all our time, and it's
just for an old assertion.
tests/test_coinmoves.py::test_generate_coinmoves (100,000, sqlite3):
Time (from start to end of l2 node): 13 seconds **WAS 34**
Worst latency: 4.0 seconds **WAS 24*
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
What changed, and why it matters
This commit removes an old debugging assertion that was causing severe performance slowdowns when many JSON-RPC commands were active. It is a pure performance optimization with no security relevance visible in the commit or supplied references.
No security action required; treat as a routine performance improvement.
Security signals we found
No strong security signals were identified.
Evidence from the diff
The patch deletes a loop in command_exec() that iterated over every command on a json_connection and asserted cmd->pending each time any command finished. This O(n) per-command completion behavior caused quadratic slowdown under high command concurrency. The commit explicitly frames this as a performance fix, not a security fix.
Changed components
lightningd/jsonrpc.cInspect captured patch +0 / −5
diff --git a/lightningd/jsonrpc.c b/lightningd/jsonrpc.c
index 5520fdce..76baaa2d 100644
--- a/lightningd/jsonrpc.c
+++ b/lightningd/jsonrpc.c
@@ -801,11 +801,6 @@ static struct command_result *command_exec(struct json_connection *jcon,
if (res == &pending)
assert(cmd->pending);
- /* The command might outlive the connection. */
- if (jcon)
- list_for_each(&jcon->commands, cmd, list)
- assert(cmd->pending);
-
return res;
}
Why this scored 15/100
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