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Detect POLLHUP/POLLRDHUP while running queries.

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Provide a new GUC check_client_connection_interval that can be used to
check whether the client connection has gone away, while running very
long queries.  It is disabled by default.

For now this uses a non-standard Linux extension (also adopted by at
least one other OS).  POLLRDHUP is not defined by POSIX, and other OSes
don't have a reliable way to know if a connection was closed without
actually trying to read or write.

In future we might consider trying to send a no-op/heartbeat message
instead, but that could require protocol changes.

Author: Sergey Cherkashin <s.cherkashin@postgrespro.ru>
Author: Thomas Munro <thomas.munro@gmail.com>
Reviewed-by: Thomas Munro <thomas.munro@gmail.com>
Reviewed-by: Tatsuo Ishii <ishii@sraoss.co.jp>
Reviewed-by: Konstantin Knizhnik <k.knizhnik@postgrespro.ru>
Reviewed-by: Zhihong Yu <zyu@yugabyte.com>
Reviewed-by: Andres Freund <andres@anarazel.de>
Reviewed-by: Maksim Milyutin <milyutinma@gmail.com>
Reviewed-by: Tsunakawa, Takayuki/綱川 貴之 <tsunakawa.takay@fujitsu.com>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us> (much earlier version)
Discussion: https://postgr.es/m/77def86b27e41f0efcba411460e929ae%40postgrespro.ru
This commit is contained in:
Thomas Munro
2021-04-03 08:52:30 +13:00
parent 174edbe9f9
commit c30f54ad73
11 changed files with 156 additions and 0 deletions
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32
src/backend/tcop/postgres.c
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@ -102,6 +102,9 @@ int max_stack_depth = 100;
/* wait N seconds to allow attach from a debugger */
int PostAuthDelay = 0;
/* Time between checks that the client is still connected. */
int client_connection_check_interval = 0;
/* ----------------
* private typedefs etc
* ----------------
@ -2671,6 +2674,14 @@ start_xact_command(void)
* not desired, the timeout has to be disabled explicitly.
*/
enable_statement_timeout();
/* Start timeout for checking if the client has gone away if necessary. */
if (client_connection_check_interval > 0 &&
IsUnderPostmaster &&
MyProcPort &&
!get_timeout_active(CLIENT_CONNECTION_CHECK_TIMEOUT))
enable_timeout_after(CLIENT_CONNECTION_CHECK_TIMEOUT,
client_connection_check_interval);
}
static void
@ -3149,6 +3160,27 @@ ProcessInterrupts(void)
(errcode(ERRCODE_ADMIN_SHUTDOWN),
errmsg("terminating connection due to administrator command")));
}
if (CheckClientConnectionPending)
{
CheckClientConnectionPending = false;
/*
* Check for lost connection and re-arm, if still configured, but not
* if we've arrived back at DoingCommandRead state. We don't want to
* wake up idle sessions, and they already know how to detect lost
* connections.
*/
if (!DoingCommandRead && client_connection_check_interval > 0)
{
if (!pq_check_connection())
ClientConnectionLost = true;
else
enable_timeout_after(CLIENT_CONNECTION_CHECK_TIMEOUT,
client_connection_check_interval);
}
}
if (ClientConnectionLost)
{
QueryCancelPending = false; /* lost connection trumps QueryCancel */