Prevent memory context logging from sending log message to connected client.

When pg_log_backend_memory_contexts() is executed, the target backend
should use LOG_SERVER_ONLY to log its memory contexts, to prevent them
from being sent to its connected client regardless of client_min_messages.
But previously the backend unexpectedly used LOG to log the message
"logging memory contexts of PID %d" and it could be sent to the client.
This is a bug in memory context logging.

To fix the bug, this commit changes that message so that it's logged with
LOG_SERVER_ONLY.

Back-patch to v14 where pg_log_backend_memory_contexts() was added.

Author: Fujii Masao
Reviewed-by: Bharath Rupireddy, Atsushi Torikoshi
Discussion: https://postgr.es/m/82c12f36-86f7-5e72-79af-7f5c37f6cad7@oss.nttdata.com

diff --git a/src/backend/utils/mmgr/mcxt.c b/src/backend/utils/mmgr/mcxt.c
index 2876f6868cb93fb06bbf868a92be1a41c51cd42b..e12be1b9bd847cba23cb2d73ed8b6831c58d6de8 100644 (file)
--- a/src/backend/utils/mmgr/mcxt.c
+++ b/src/backend/utils/mmgr/mcxt.c
@@ -1042,8 +1042,14 @@ ProcessLogMemoryContextInterrupt(void)
 {
    LogMemoryContextPending = false;
 
-   ereport(LOG,
-           (errmsg("logging memory contexts of PID %d", MyProcPid)));
+   /*
+    * Use LOG_SERVER_ONLY to prevent this message from being sent to the
+    * connected client.
+    */
+   ereport(LOG_SERVER_ONLY,
+           (errhidestmt(true),
+            errhidecontext(true),
+            errmsg("logging memory contexts of PID %d", MyProcPid)));
 
    /*
     * When a backend process is consuming huge memory, logging all its memory