atproto relay implementation in zig
zlay.waow.tech
add broadcast queue push-lock spin counter
separates push-lock contention from queue-full contention so operator
can distinguish: producers fighting for the CAS lock vs producers
blocked on a full ring buffer.
new metric: relay_broadcast_queue_push_lock_spins_total
clarified: relay_broadcast_queue_full_total HELP text (ring capacity)
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
+12
-1
+12
-1
src/broadcaster.zig
+12
-1
src/broadcaster.zig
···
59
59
pool_queued_bytes: std.atomic.Value(u64) = .{ .raw = 0 },
60
60
// persist/broadcast pipeline contention
61
61
persist_order_spins: std.atomic.Value(u64) = .{ .raw = 0 },
62
+
broadcast_queue_push_lock_spins: std.atomic.Value(u64) = .{ .raw = 0 },
62
63
broadcast_queue_full: std.atomic.Value(u64) = .{ .raw = 0 },
63
64
broadcast_queue_depth_hwm: std.atomic.Value(u32) = .{ .raw = 0 },
64
65
broadcast_no_consumers: std.atomic.Value(u64) = .{ .raw = 0 },
···
275
276
var full_spins: u32 = 0;
276
277
while (true) {
277
278
// acquire spinlock
279
+
var lock_spins: u32 = 0;
278
280
while (self.push_lock.cmpxchgWeak(0, 1, .acquire, .monotonic) != null) {
281
+
lock_spins += 1;
279
282
std.atomic.spinLoopHint();
283
+
}
284
+
if (lock_spins > 0) {
285
+
_ = stats.broadcast_queue_push_lock_spins.fetchAdd(lock_spins, .monotonic);
280
286
}
281
287
282
288
const tail = self.tail.load(.monotonic);
···
970
976
\\# HELP relay_persist_order_spins_total spin iterations waiting for persist ordering lock
971
977
\\relay_persist_order_spins_total {d}
972
978
\\
979
+
\\# TYPE relay_broadcast_queue_push_lock_spins_total counter
980
+
\\# HELP relay_broadcast_queue_push_lock_spins_total spin iterations waiting for broadcast queue push lock
981
+
\\relay_broadcast_queue_push_lock_spins_total {d}
982
+
\\
973
983
\\# TYPE relay_broadcast_queue_full_total counter
974
-
\\# HELP relay_broadcast_queue_full_total spin iterations on full broadcast queue
984
+
\\# HELP relay_broadcast_queue_full_total spin iterations on full broadcast queue (ring capacity)
975
985
\\relay_broadcast_queue_full_total {d}
976
986
\\
977
987
\\# TYPE relay_broadcast_queue_depth_hwm gauge
···
984
994
\\
985
995
, .{
986
996
stats.persist_order_spins.load(.acquire),
997
+
stats.broadcast_queue_push_lock_spins.load(.acquire),
987
998
stats.broadcast_queue_full.load(.acquire),
988
999
stats.broadcast_queue_depth_hwm.load(.acquire),
989
1000
stats.broadcast_no_consumers.load(.acquire),