Suppress duplicate error messages in pq_flush. Write error messages to

postmaster log with elog(DEBUG) so that they will be timestamped etc.
Once upon a time I think elog() was unsafe here, but it shouldn't be anymore.

diff --git a/src/backend/libpq/pqcomm.c b/src/backend/libpq/pqcomm.c
index f3964997bea65d712a19add48eadadbb1643f7cb..181c46416b7a05d16201ba7a2ab6e7026efa6628 100644 (file)
--- a/src/backend/libpq/pqcomm.c
+++ b/src/backend/libpq/pqcomm.c
@@ -29,7 +29,7 @@
  * Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- *     $Id: pqcomm.c,v 1.123 2001/11/05 17:46:25 momjian Exp $
+ *     $Id: pqcomm.c,v 1.124 2001/11/12 04:54:08 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -503,19 +503,18 @@ pq_recvbuf(void)
                                continue;               /* Ok if interrupted */
 
                        /*
-                        * We would like to use elog() here, but dare not because elog
-                        * tries to write to the client, which will cause problems if
-                        * we have a hard communications failure ... So just write the
-                        * message to the postmaster log.
+                        * Careful: an elog() that tries to write to the client
+                        * would cause recursion to here, leading to stack overflow
+                        * and core dump!  This message must go *only* to the postmaster
+                        * log.  elog(DEBUG) is presently safe.
                         */
-                       fprintf(stderr, "pq_recvbuf: recv() failed: %s\n",
-                                       strerror(errno));
+                       elog(DEBUG, "pq_recvbuf: recv() failed: %m");
                        return EOF;
                }
                if (r == 0)
                {
-                       /* as above, elog not safe */
-                       fprintf(stderr, "pq_recvbuf: unexpected EOF on client connection\n");
+                       /* as above, only write to postmaster log */
+                       elog(DEBUG, "pq_recvbuf: unexpected EOF on client connection");
                        return EOF;
                }
                /* r contains number of bytes read, so just incr length */
@@ -655,6 +654,8 @@ pq_putbytes(const char *s, size_t len)
 int
 pq_flush(void)
 {
+       static int last_reported_send_errno = 0;
+
        unsigned char *bufptr = PqSendBuffer;
        unsigned char *bufend = PqSendBuffer + PqSendPointer;
 
@@ -675,12 +676,20 @@ pq_flush(void)
                                continue;               /* Ok if we were interrupted */
 
                        /*
-                        * We would like to use elog() here, but cannot because elog
-                        * tries to write to the client, which would cause a recursive
-                        * flush attempt!  So just write it out to the postmaster log.
+                        * Careful: an elog() that tries to write to the client
+                        * would cause recursion to here, leading to stack overflow
+                        * and core dump!  This message must go *only* to the postmaster
+                        * log.  elog(DEBUG) is presently safe.
+                        *
+                        * If a client disconnects while we're in the midst of output,
+                        * we might write quite a bit of data before we get to a safe
+                        * query abort point.  So, suppress duplicate log messages.
                         */
-                       fprintf(stderr, "pq_flush: send() failed: %s\n",
-                                       strerror(errno));
+                       if (errno != last_reported_send_errno)
+                       {
+                               last_reported_send_errno = errno;
+                               elog(DEBUG, "pq_flush: send() failed: %m");
+                       }
 
                        /*
                         * We drop the buffered data anyway so that processing can
@@ -689,8 +698,11 @@ pq_flush(void)
                        PqSendPointer = 0;
                        return EOF;
                }
+
+               last_reported_send_errno = 0; /* reset after any successful send */
                bufptr += r;
        }
+
        PqSendPointer = 0;
        return 0;
 }
@@ -709,8 +721,8 @@ pq_eof(void)
 
        if (res < 0)
        {
-               /* don't try to elog here... */
-               fprintf(stderr, "pq_eof: recv() failed: %s\n", strerror(errno));
+               /* can log to postmaster log only */
+               elog(DEBUG, "pq_eof: recv() failed: %m");
                return EOF;
        }
        if (res == 0)