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Commit3c485ca

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Further improvements in pg_ctl's new wait-for-postmaster-start logic.
Add a postmaster_is_alive() test to the wait loop, so that we stop waitingif the postmaster dies without removing its pidfile. Unfortunately thisonly helps after the postmaster has created its pidfile, since until thenwe don't know which PID to check. But if it never does create the pidfile,we can give up in a relatively short time, so this is a useful additionin practice. Per suggestion from Fujii Masao, though this doesn't lookvery much like his patch.In addition, improve pg_ctl's ability to cope with pre-existing pidfiles.Such a file might or might not represent a live postmaster that is going toblock our postmaster from starting, but the previous code pre-judged thesituation and gave up waiting immediately. Now, we will wait for up to 5seconds to see if our postmaster overwrites such a file. This issueinteracts with Fujii's patch because we would make the wrong conclusionif we did the postmaster_is_alive() test with a pre-existing PID.All of this could be improved if we rewrote start_postmaster() so that itcould report the child postmaster's PID, so that we'd know a-priori thecorrect PID to test with postmaster_is_alive(). That looks like a bit toomuch change for so late in the 9.1 development cycle, unfortunately.
1 parent6923d69 commit3c485ca

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1 file changed

+94
-66
lines changed

1 file changed

+94
-66
lines changed

‎src/bin/pg_ctl/pg_ctl.c‎

Lines changed: 94 additions & 66 deletions
Original file line numberDiff line numberDiff line change
@@ -366,6 +366,10 @@ start_postmaster(void)
366366
/*
367367
* Since there might be quotes to handle here, it is easier simply to pass
368368
* everything to a shell to process them.
369+
*
370+
* XXX it would be better to fork and exec so that we would know the
371+
* child postmaster's PID directly; then test_postmaster_connection could
372+
* use the PID without having to rely on reading it back from the pidfile.
369373
*/
370374
if (log_file!=NULL)
371375
snprintf(cmd,MAXPGPATH,SYSTEMQUOTE"\"%s\" %s%s < \"%s\" >> \"%s\" 2>&1 &"SYSTEMQUOTE,
@@ -412,6 +416,8 @@ static PGPing
412416
test_postmaster_connection(booldo_checkpoint)
413417
{
414418
PGPingret=PQPING_NO_RESPONSE;
419+
boolfound_stale_pidfile= false;
420+
pgpid_tpm_pid=0;
415421
charconnstr[MAXPGPATH*2+256];
416422
inti;
417423

@@ -458,78 +464,94 @@ test_postmaster_connection(bool do_checkpoint)
458464
if (optlines[3]==NULL)
459465
{
460466
/* File is exactly three lines, must be pre-9.1 */
461-
write_stderr(_("%s: -w option is not supported when starting a pre-9.1 server\n"),
467+
write_stderr(_("\n%s: -w option is not supported when starting a pre-9.1 server\n"),
462468
progname);
463469
returnPQPING_NO_ATTEMPT;
464470
}
465471
elseif (optlines[4]!=NULL&&
466472
optlines[5]!=NULL)
467473
{
468474
/* File is complete enough for us, parse it */
475+
longpmpid;
469476
time_tpmstart;
470-
intportnum;
471-
char*sockdir;
472-
char*hostaddr;
473-
charhost_str[MAXPGPATH];
474477

475478
/*
476-
* Easy cross-check that we are looking at the right data
477-
* directory: is the postmaster older than this execution
478-
* of pg_ctl? Subtract 2 seconds to allow for possible
479-
* clock skew between pg_ctl and the postmaster.
479+
* Make sanity checks. If it's for a standalone backend
480+
* (negative PID), or the recorded start time is before
481+
* pg_ctl started, then either we are looking at the wrong
482+
* data directory, or this is a pre-existing pidfile that
483+
* hasn't (yet?) been overwritten by our child postmaster.
484+
* Allow 2 seconds slop for possible cross-process clock
485+
* skew.
480486
*/
487+
pmpid=atol(optlines[LOCK_FILE_LINE_PID-1]);
481488
pmstart=atol(optlines[LOCK_FILE_LINE_START_TIME-1]);
482-
if (pmstart<start_time-2)
489+
if (pmpid <=0||pmstart<start_time-2)
483490
{
484-
write_stderr(_("%s: this data directory is running a pre-existing postmaster\n"),
485-
progname);
486-
returnPQPING_NO_ATTEMPT;
491+
/*
492+
* Set flag to report stale pidfile if it doesn't
493+
* get overwritten before we give up waiting.
494+
*/
495+
found_stale_pidfile= true;
487496
}
497+
else
498+
{
499+
/*
500+
* OK, seems to be a valid pidfile from our child.
501+
*/
502+
intportnum;
503+
char*sockdir;
504+
char*hostaddr;
505+
charhost_str[MAXPGPATH];
488506

489-
/*
490-
* OK, extract port number and host string to use. Prefer
491-
* using Unix socket if available.
492-
*/
493-
portnum=atoi(optlines[LOCK_FILE_LINE_PORT-1]);
507+
found_stale_pidfile= false;
508+
pm_pid= (pgpid_t)pmpid;
494509

495-
sockdir=optlines[LOCK_FILE_LINE_SOCKET_DIR-1];
496-
hostaddr=optlines[LOCK_FILE_LINE_LISTEN_ADDR-1];
510+
/*
511+
* Extract port number and host string to use. Prefer
512+
* using Unix socket if available.
513+
*/
514+
portnum=atoi(optlines[LOCK_FILE_LINE_PORT-1]);
515+
sockdir=optlines[LOCK_FILE_LINE_SOCKET_DIR-1];
516+
hostaddr=optlines[LOCK_FILE_LINE_LISTEN_ADDR-1];
497517

498-
/*
499-
* While unix_socket_directory can accept relative
500-
* directories, libpq's host parameter must have a leading
501-
* slash to indicate a socket directory. So, ignore
502-
* sockdir if it's relative, and try to use TCP instead.
503-
*/
504-
if (sockdir[0]=='/')
505-
strlcpy(host_str,sockdir,sizeof(host_str));
506-
else
507-
strlcpy(host_str,hostaddr,sizeof(host_str));
518+
/*
519+
* While unix_socket_directory can accept relative
520+
* directories, libpq's host parameter must have a
521+
* leading slash to indicate a socket directory. So,
522+
* ignore sockdir if it's relative, and try to use TCP
523+
* instead.
524+
*/
525+
if (sockdir[0]=='/')
526+
strlcpy(host_str,sockdir,sizeof(host_str));
527+
else
528+
strlcpy(host_str,hostaddr,sizeof(host_str));
508529

509-
/* remove trailing newline */
510-
if (strchr(host_str,'\n')!=NULL)
511-
*strchr(host_str,'\n')='\0';
530+
/* remove trailing newline */
531+
if (strchr(host_str,'\n')!=NULL)
532+
*strchr(host_str,'\n')='\0';
512533

513-
/* Fail if we couldn't get either sockdir or host addr */
514-
if (host_str[0]=='\0')
515-
{
516-
write_stderr(_("%s: -w option cannot use a relative socket directory specification\n"),
517-
progname);
518-
returnPQPING_NO_ATTEMPT;
519-
}
534+
/* Fail if couldn't get either sockdir or host addr */
535+
if (host_str[0]=='\0')
536+
{
537+
write_stderr(_("\n%s: -w option cannot use a relative socket directory specification\n"),
538+
progname);
539+
returnPQPING_NO_ATTEMPT;
540+
}
520541

521-
/* If postmaster is listening on "*", use"localhost" */
522-
if (strcmp(host_str,"*")==0)
523-
strcpy(host_str,"localhost");
542+
/* If postmaster is listening on "*", use localhost */
543+
if (strcmp(host_str,"*")==0)
544+
strcpy(host_str,"localhost");
524545

525-
/*
526-
* We need to set connect_timeout otherwise on Windows the
527-
* Service Control Manager (SCM) will probably timeout
528-
* first.
529-
*/
530-
snprintf(connstr,sizeof(connstr),
531-
"dbname=postgres port=%d host='%s' connect_timeout=5",
532-
portnum,host_str);
546+
/*
547+
* We need to set connect_timeout otherwise on Windows
548+
* the Service Control Manager (SCM) will probably
549+
* timeout first.
550+
*/
551+
snprintf(connstr,sizeof(connstr),
552+
"dbname=postgres port=%d host='%s' connect_timeout=5",
553+
portnum,host_str);
554+
}
533555
}
534556
}
535557
}
@@ -545,16 +567,36 @@ test_postmaster_connection(bool do_checkpoint)
545567
/*
546568
* The postmaster should create postmaster.pid very soon after being
547569
* started. If it's not there after we've waited 5 or more seconds,
548-
* assume startup failed and give up waiting.
570+
* assume startup failed and give up waiting. (Note this covers
571+
* both cases where the pidfile was never created, and where it was
572+
* created and then removed during postmaster exit.) Also, if there
573+
* *is* a file there but it appears stale, issue a suitable warning
574+
* and give up waiting.
549575
*/
550576
if (i >=5)
551577
{
552578
structstatstatbuf;
553579

554580
if (stat(pid_file,&statbuf)!=0)
555581
returnPQPING_NO_RESPONSE;
582+
583+
if (found_stale_pidfile)
584+
{
585+
write_stderr(_("\n%s: this data directory appears to be running a pre-existing postmaster\n"),
586+
progname);
587+
returnPQPING_NO_RESPONSE;
588+
}
556589
}
557590

591+
/*
592+
* If we've been able to identify the child postmaster's PID, check
593+
* the process is still alive. This covers cases where the postmaster
594+
* successfully created the pidfile but then crashed without removing
595+
* it.
596+
*/
597+
if (pm_pid>0&& !postmaster_is_alive((pid_t)pm_pid))
598+
returnPQPING_NO_RESPONSE;
599+
558600
/* No response, or startup still in process; wait */
559601
#if defined(WIN32)
560602
if (do_checkpoint)
@@ -715,7 +757,6 @@ do_init(void)
715757
staticvoid
716758
do_start(void)
717759
{
718-
pgpid_tpid;
719760
pgpid_told_pid=0;
720761
intexitcode;
721762

@@ -765,19 +806,6 @@ do_start(void)
765806
exit(1);
766807
}
767808

768-
if (old_pid!=0)
769-
{
770-
pg_usleep(1000000);
771-
pid=get_pgpid();
772-
if (pid==old_pid)
773-
{
774-
write_stderr(_("%s: could not start server\n"
775-
"Examine the log output.\n"),
776-
progname);
777-
exit(1);
778-
}
779-
}
780-
781809
if (do_wait)
782810
{
783811
print_msg(_("waiting for server to start..."));

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