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Guard tune_timeout_for_session_needs_pause from stale pause_until #5784

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Guard tune_timeout_for_session_needs_pause from stale pause_until #5784

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1430f50
prevent poll_timeout corruption from stale pause_until
rahim-kanji May 13, 2026
9887933
Remove comment
rahim-kanji May 19, 2026
ee1793d
Merge branch 'v3.0' into v3.0_fix-stale-pause-until
renecannao May 25, 2026
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16 changes: 13 additions & 3 deletions lib/Base_Thread.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -347,9 +347,19 @@ void Base_Thread::tune_timeout_for_myds_needs_pause(DS * myds) {
template<typename T, typename DS>
void Base_Thread::tune_timeout_for_session_needs_pause(DS * myds) {
T* thr = static_cast<T*>(this);
if (thr->mypolls.poll_timeout==0 || (myds->sess->pause_until - curtime < thr->mypolls.poll_timeout) ) {
thr->mypolls.poll_timeout= myds->sess->pause_until - curtime;
proxy_debug(PROXY_DEBUG_MYSQL_CONNECTION, 7, "Session=%p , poll_timeout=%u , pause_until=%llu , curtime=%llu\n", myds->sess, thr->mypolls.poll_timeout, myds->sess->pause_until, curtime);

// Only adjust poll_timeout if the pause is still in the future. If pause_until
// is stale (already <= curtime), computing (pause_until - curtime) as unsigned
// would underflow to ~1.8e19 and corrupt poll_timeout, making poll() fall back
// to the default timeout (~2s) and stalling the worker thread. The stale-pause
// case is handled by check_timing_out_session (AfterPoll) and the handler-entry
// pause checks, so doing nothing here is correct.
if (myds->sess->pause_until > curtime) {
if (thr->mypolls.poll_timeout == 0 || (myds->sess->pause_until - curtime < thr->mypolls.poll_timeout)) {
thr->mypolls.poll_timeout = myds->sess->pause_until - curtime;
proxy_debug(PROXY_DEBUG_MYSQL_CONNECTION, 7, "Session=%p , poll_timeout=%u , pause_until=%llu , curtime=%llu\n", myds->sess, thr->mypolls.poll_timeout,
myds->sess->pause_until, curtime);
}
}
}
Comment on lines +357 to 364

@gemini-code-assist gemini-code-assist Bot May 13, 2026

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high

The logic for handling expired pauses should be enabled, and a unit mismatch in the timeout calculation needs to be addressed:

  1. Expired Pauses: The commented-out else block should be active. If pause_until <= curtime, the session is ready for processing. By not updating poll_timeout to a small value (like 1ms), the thread may block for the default timeout (2000ms), causing the freeze described in the PR summary.
  2. Unit Mismatch: pause_until - curtime is in microseconds, but poll_timeout is compared downstream against a millisecond value (2000 ms). If poll_timeout is set to microseconds, the comparison timeout < 2000 will fail for any pause longer than 2ms, causing the tuning to be ignored. The difference should be converted to milliseconds.
	if (myds->sess->pause_until > curtime) {
		// Future pause: align poll_timeout to the pause expiration.
		// Convert microseconds to milliseconds (ceiling division)
		unsigned int timeout_ms = (myds->sess->pause_until - curtime + 999) / 1000;
		if (thr->mypolls.poll_timeout == 0 || timeout_ms < (unsigned int)thr->mypolls.poll_timeout) {
			thr->mypolls.poll_timeout = timeout_ms;
			proxy_debug(PROXY_DEBUG_MYSQL_CONNECTION, 7, "Session=%p , poll_timeout=%u , pause_until=%llu , curtime=%llu\n", myds->sess, thr->mypolls.poll_timeout, 
				myds->sess->pause_until, curtime);
		}
	} else {
		// pause_until > 0 (caller checked) but <= curtime: pause has already expired.
		// Wake poll() immediately rather than computing (pause_until - curtime)
		if (thr->mypolls.poll_timeout == 0 || thr->mypolls.poll_timeout > 1) {
			thr->mypolls.poll_timeout = 1;
		}
	}


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3 changes: 2 additions & 1 deletion lib/MySQL_Session.cpp
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Expand Up @@ -3013,6 +3013,7 @@ bool MySQL_Session::handler_again___status_CONNECTING_SERVER(int *_rc) {

st=previous_status.top();
previous_status.pop();
pause_until = 0;
NEXT_IMMEDIATE_NEW(st);
}
assert(st==status);
Expand All @@ -3039,7 +3040,7 @@ bool MySQL_Session::handler_again___status_CONNECTING_SERVER(int *_rc) {
st=previous_status.top();
previous_status.pop();
myds->wait_until=0;

pause_until = 0;
if (handle_session_track_capabilities() == false) {
previous_status.push(st);
pause_until = thread->curtime + mysql_thread___connect_retries_delay * 1000;
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2 changes: 2 additions & 0 deletions lib/PgSQL_Session.cpp
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Expand Up @@ -1634,6 +1634,7 @@ bool PgSQL_Session::handler_again___status_CONNECTING_SERVER(int* _rc) {
if (mybe->server_myds->myconn->async_state_machine == ASYNC_IDLE) {
st = previous_status.top();
previous_status.pop();
pause_until = 0;
NEXT_IMMEDIATE_NEW(st);
}
assert(st == status);
Expand Down Expand Up @@ -1671,6 +1672,7 @@ bool PgSQL_Session::handler_again___status_CONNECTING_SERVER(int* _rc) {
st = previous_status.top();
previous_status.pop();
myds->wait_until = 0;
pause_until = 0;
if (session_fast_forward) {
// we have a successful connection and session_fast_forward enabled
// set DSS=STATE_SLEEP or it will believe it have to use MARIADB client library
Expand Down
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