Detect POLLHUP/POLLRDHUP while running queries.

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 <[email protected]>
Author: Thomas Munro <[email protected]>
Reviewed-by: Thomas Munro <[email protected]>
Reviewed-by: Tatsuo Ishii <[email protected]>
Reviewed-by: Konstantin Knizhnik <[email protected]>
Reviewed-by: Zhihong Yu <[email protected]>
Reviewed-by: Andres Freund <[email protected]>
Reviewed-by: Maksim Milyutin <[email protected]>
Reviewed-by: Tsunakawa, Takayuki/綱川 貴之 <[email protected]>
Reviewed-by: Tom Lane <[email protected]> (much earlier version)
Discussion: https://postgr.es/m/77def86b27e41f0efcba411460e929ae%40postgrespro.ru

1 files changed, 3 insertions, 0 deletions

diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index 30cfddac1f7..39da7cc9427 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -719,6 +719,9 @@
 
 #dynamic_library_path = '$libdir'
 
+#client_connection_check_interval = 0	# time between checks for client
+					# disconnection while running queries;
+					# 0 for never
 
 #------------------------------------------------------------------------------
 # LOCK MANAGEMENT