I discussed this elsewhere [0], but I thought it deserved its own thread.
After setting wal_retrieve_retry_interval to 1ms in the tests, I noticed
that some of the archiving tests began consistently failing on Windows. I
believe the problem is that WaitForWALToBecomeAvailable() depends on the
call to WaitLatch() for wal_retrieve_retry_interval to ensure that signals
are dispatched (i.e., pgwin32_dispatch_queued_signals()). With a low retry
interval, WaitForWALToBecomeAvailable() might skip the call to WaitLatch(),
and the signals are never processed.
The attached patch fixes this by always calling WaitLatch(), even if
wal_retrieve_retry_interval milliseconds have already elapsed and the
timeout is 0.
[0] https://postgr.es/m/20221231235019.GA1223171%40nathanxps13
--
Nathan Bossart
Amazon Web Services: https://aws.amazon.com
>From d08f01156ce1ce1290bad440da97852c2aa6c24b Mon Sep 17 00:00:00 2001
From: Nathan Bossart <nathandboss...@gmail.com>
Date: Sat, 31 Dec 2022 15:16:54 -0800
Subject: [PATCH v1 1/1] ensure signals are dispatched in startup process on
Windows
---
src/backend/access/transam/xlogrecovery.c | 36 ++++++++++++++---------
1 file changed, 22 insertions(+), 14 deletions(-)
diff --git a/src/backend/access/transam/xlogrecovery.c b/src/backend/access/transam/xlogrecovery.c
index bc3c3eb3e7..b1a4c4ab6d 100644
--- a/src/backend/access/transam/xlogrecovery.c
+++ b/src/backend/access/transam/xlogrecovery.c
@@ -3466,6 +3466,8 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
*/
if (lastSourceFailed)
{
+ long wait_time;
+
/*
* Don't allow any retry loops to occur during nonblocking
* readahead. Let the caller process everything that has been
@@ -3556,33 +3558,39 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
* and retry from the archive, but if it hasn't been long
* since last attempt, sleep wal_retrieve_retry_interval
* milliseconds to avoid busy-waiting.
+ *
+ * NB: Even if it's already been wal_retrieve_rety_interval
+ * milliseconds since the last attempt, we still call
+ * WaitLatch() with the timeout set to 0 to make sure any
+ * queued signals are dispatched on Windows builds.
*/
now = GetCurrentTimestamp();
if (!TimestampDifferenceExceeds(last_fail_time, now,
wal_retrieve_retry_interval))
{
- long wait_time;
-
wait_time = wal_retrieve_retry_interval -
TimestampDifferenceMilliseconds(last_fail_time, now);
elog(LOG, "waiting for WAL to become available at %X/%X",
LSN_FORMAT_ARGS(RecPtr));
+ }
+ else
+ wait_time = 0;
- /* Do background tasks that might benefit us later. */
- KnownAssignedTransactionIdsIdleMaintenance();
+ /* Do background tasks that might benefit us later. */
+ KnownAssignedTransactionIdsIdleMaintenance();
- (void) WaitLatch(&XLogRecoveryCtl->recoveryWakeupLatch,
- WL_LATCH_SET | WL_TIMEOUT |
- WL_EXIT_ON_PM_DEATH,
- wait_time,
- WAIT_EVENT_RECOVERY_RETRIEVE_RETRY_INTERVAL);
- ResetLatch(&XLogRecoveryCtl->recoveryWakeupLatch);
- now = GetCurrentTimestamp();
+ (void) WaitLatch(&XLogRecoveryCtl->recoveryWakeupLatch,
+ WL_LATCH_SET | WL_TIMEOUT |
+ WL_EXIT_ON_PM_DEATH,
+ wait_time,
+ WAIT_EVENT_RECOVERY_RETRIEVE_RETRY_INTERVAL);
+ ResetLatch(&XLogRecoveryCtl->recoveryWakeupLatch);
+ now = GetCurrentTimestamp();
+
+ /* Handle interrupt signals of startup process */
+ HandleStartupProcInterrupts();
- /* Handle interrupt signals of startup process */
- HandleStartupProcInterrupts();
- }
last_fail_time = now;
currentSource = XLOG_FROM_ARCHIVE;
break;
--
2.25.1
