Revert "Fix "pg_ctl start -w" to test child process status directly."

This reverts commit c869a7d5b44e7164fadfb638786def05d510312a.
As pointed out by Maksym Sobolyev in bug #14199, that approach doesn't
work if the postmaster forks itself an extra time due to silent_mode
being enabled.  We removed silent_mode in 9.2, so the pg_ctl change is
fine in 9.2 and later, but it fails when that option is enabled in 9.1.
Seeing that 9.1 is close to end-of-life, let's adopt the most conservative
fix we can, which is to revert the pg_ctl change in the 9.1 branch.

Discussion: <20160618042812.5798.85609@wrigleys.postgresql.org>

diff --git a/src/bin/pg_ctl/pg_ctl.c b/src/bin/pg_ctl/pg_ctl.c
index 16aad55fe3c982b69d22d698b603845de981bd01..817c37dc643c0a06baa9d90ba036c1e70fac7029 100644 (file)
--- a/src/bin/pg_ctl/pg_ctl.c
+++ b/src/bin/pg_ctl/pg_ctl.c
@@ -28,7 +28,6 @@
 #include <time.h>
 #include <sys/types.h>
 #include <sys/stat.h>
-#include <sys/wait.h>
 #include <unistd.h>
 
 #ifdef HAVE_SYS_RESOURCE_H
@@ -155,10 +154,10 @@ static int pgwin32_is_service(void);
 
 static pgpid_t get_pgpid(void);
 static char **readfile(const char *path);
-static pgpid_t start_postmaster(void);
+static int start_postmaster(void);
 static void read_post_opts(void);
 
-static PGPing test_postmaster_connection(pgpid_t pm_pid, bool do_checkpoint);
+static PGPing test_postmaster_connection(bool);
 static bool postmaster_is_alive(pid_t pid);
 
 #if defined(HAVE_GETRLIMIT) && defined(RLIMIT_CORE)
@@ -402,73 +401,36 @@ readfile(const char *path)
  * start/test/stop routines
  */
 
-/*
- * Start the postmaster and return its PID.
- *
- * Currently, on Windows what we return is the PID of the shell process
- * that launched the postmaster (and, we trust, is waiting for it to exit).
- * So the PID is usable for "is the postmaster still running" checks,
- * but cannot be compared directly to postmaster.pid.
- *
- * On Windows, we also save aside a handle to the shell process in
- * "postmasterProcess", which the caller should close when done with it.
- */
-static pgpid_t
+static int
 start_postmaster(void)
 {
    char        cmd[MAXPGPATH];
 
 #ifndef WIN32
-   pgpid_t     pm_pid;
-
-   /* Flush stdio channels just before fork, to avoid double-output problems */
-   fflush(stdout);
-   fflush(stderr);
-
-   pm_pid = fork();
-   if (pm_pid < 0)
-   {
-       /* fork failed */
-       write_stderr(_("%s: could not start server: %s\n"),
-                    progname, strerror(errno));
-       exit(1);
-   }
-   if (pm_pid > 0)
-   {
-       /* fork succeeded, in parent */
-       return pm_pid;
-   }
-
-   /* fork succeeded, in child */
 
    /*
     * Since there might be quotes to handle here, it is easier simply to pass
-    * everything to a shell to process them.  Use exec so that the postmaster
-    * has the same PID as the current child process.
+    * everything to a shell to process them.
+    *
+    * XXX it would be better to fork and exec so that we would know the child
+    * postmaster's PID directly; then test_postmaster_connection could use
+    * the PID without having to rely on reading it back from the pidfile.
     */
    if (log_file != NULL)
-       snprintf(cmd, MAXPGPATH, "exec \"%s\" %s%s < \"%s\" >> \"%s\" 2>&1",
+       snprintf(cmd, MAXPGPATH, SYSTEMQUOTE "\"%s\" %s%s < \"%s\" >> \"%s\" 2>&1 &" SYSTEMQUOTE,
                 exec_path, pgdata_opt, post_opts,
                 DEVNULL, log_file);
    else
-       snprintf(cmd, MAXPGPATH, "exec \"%s\" %s%s < \"%s\" 2>&1",
+       snprintf(cmd, MAXPGPATH, SYSTEMQUOTE "\"%s\" %s%s < \"%s\" 2>&1 &" SYSTEMQUOTE,
                 exec_path, pgdata_opt, post_opts, DEVNULL);
 
-   (void) execl("/bin/sh", "/bin/sh", "-c", cmd, (char *) NULL);
-
-   /* exec failed */
-   write_stderr(_("%s: could not start server: %s\n"),
-                progname, strerror(errno));
-   exit(1);
-
-   return 0;                   /* keep dumb compilers quiet */
-
+   return system(cmd);
 #else                          /* WIN32 */
 
    /*
-    * As with the Unix case, it's easiest to use the shell (CMD.EXE) to
-    * handle redirection etc.  Unfortunately CMD.EXE lacks any equivalent of
-    * "exec", so we don't get to find out the postmaster's PID immediately.
+    * On win32 we don't use system(). So we don't need to use & (which would
+    * be START /B on win32). However, we still call the shell (CMD.EXE) with
+    * it to handle redirection etc.
     */
    PROCESS_INFORMATION pi;
 
@@ -480,15 +442,10 @@ start_postmaster(void)
                 exec_path, pgdata_opt, post_opts, DEVNULL);
 
    if (!CreateRestrictedProcess(cmd, &pi, false))
-   {
-       write_stderr(_("%s: could not start server: error code %lu\n"),
-                    progname, (unsigned long) GetLastError());
-       exit(1);
-   }
-   /* Don't close command process handle here; caller must do so */
-   postmasterProcess = pi.hProcess;
+       return GetLastError();
+   CloseHandle(pi.hProcess);
    CloseHandle(pi.hThread);
-   return pi.dwProcessId;      /* Shell's PID, not postmaster's! */
+   return 0;
 #endif   /* WIN32 */
 }
 
@@ -497,21 +454,15 @@ start_postmaster(void)
 /*
  * Find the pgport and try a connection
  *
- * On Unix, pm_pid is the PID of the just-launched postmaster.  On Windows,
- * it may be the PID of an ancestor shell process, so we can't check the
- * contents of postmaster.pid quite as carefully.
- *
- * On Windows, the static variable postmasterProcess is an implicit argument
- * to this routine; it contains a handle to the postmaster process or an
- * ancestor shell process thereof.
- *
  * Note that the checkpoint parameter enables a Windows service control
  * manager checkpoint, it's got nothing to do with database checkpoints!!
  */
 static PGPing
-test_postmaster_connection(pgpid_t pm_pid, bool do_checkpoint)
+test_postmaster_connection(bool do_checkpoint)
 {
    PGPing      ret = PQPING_NO_RESPONSE;
+   bool        found_stale_pidfile = false;
+   pgpid_t     pm_pid = 0;
    char        connstr[MAXPGPATH * 2 + 256];
    int         i;
 
@@ -566,27 +517,29 @@ test_postmaster_connection(pgpid_t pm_pid, bool do_checkpoint)
                         optlines[5] != NULL)
                {
                    /* File is complete enough for us, parse it */
-                   pgpid_t     pmpid;
+                   long        pmpid;
                    time_t      pmstart;
 
                    /*
-                    * Make sanity checks.  If it's for the wrong PID, or the
-                    * recorded start time is before pg_ctl started, then
-                    * either we are looking at the wrong data directory, or
-                    * this is a pre-existing pidfile that hasn't (yet?) been
-                    * overwritten by our child postmaster.  Allow 2 seconds
-                    * slop for possible cross-process clock skew.
+                    * Make sanity checks.  If it's for a standalone backend
+                    * (negative PID), or the recorded start time is before
+                    * pg_ctl started, then either we are looking at the wrong
+                    * data directory, or this is a pre-existing pidfile that
+                    * hasn't (yet?) been overwritten by our child postmaster.
+                    * Allow 2 seconds slop for possible cross-process clock
+                    * skew.
                     */
                    pmpid = atol(optlines[LOCK_FILE_LINE_PID - 1]);
                    pmstart = atol(optlines[LOCK_FILE_LINE_START_TIME - 1]);
-                   if (pmstart >= start_time - 2 &&
-#ifndef WIN32
-                       pmpid == pm_pid
-#else
-                   /* Windows can only reject standalone-backend PIDs */
-                       pmpid > 0
-#endif
-                       )
+                   if (pmpid <= 0 || pmstart < start_time - 2)
+                   {
+                       /*
+                        * Set flag to report stale pidfile if it doesn't get
+                        * overwritten before we give up waiting.
+                        */
+                       found_stale_pidfile = true;
+                   }
+                   else
                    {
                        /*
                         * OK, seems to be a valid pidfile from our child.
@@ -596,6 +549,9 @@ test_postmaster_connection(pgpid_t pm_pid, bool do_checkpoint)
                        char       *hostaddr;
                        char        host_str[MAXPGPATH];
 
+                       found_stale_pidfile = false;
+                       pm_pid = (pgpid_t) pmpid;
+
                        /*
                         * Extract port number and host string to use. Prefer
                         * using Unix socket if available.
@@ -667,23 +623,37 @@ test_postmaster_connection(pgpid_t pm_pid, bool do_checkpoint)
        }
 
        /*
-        * Check whether the child postmaster process is still alive.  This
-        * lets us exit early if the postmaster fails during startup.
-        *
-        * On Windows, we may be checking the postmaster's parent shell, but
-        * that's fine for this purpose.
+        * The postmaster should create postmaster.pid very soon after being
+        * started.  If it's not there after we've waited 5 or more seconds,
+        * assume startup failed and give up waiting.  (Note this covers both
+        * cases where the pidfile was never created, and where it was created
+        * and then removed during postmaster exit.)  Also, if there *is* a
+        * file there but it appears stale, issue a suitable warning and give
+        * up waiting.
         */
-#ifndef WIN32
+       if (i >= 5)
        {
-           int         exitstatus;
+           struct stat statbuf;
+
+           if (stat(pid_file, &statbuf) != 0)
+               return PQPING_NO_RESPONSE;
 
-           if (waitpid((pid_t) pm_pid, &exitstatus, WNOHANG) == (pid_t) pm_pid)
+           if (found_stale_pidfile)
+           {
+               write_stderr(_("\n%s: this data directory appears to be running a pre-existing postmaster\n"),
+                            progname);
                return PQPING_NO_RESPONSE;
+           }
        }
-#else
-       if (WaitForSingleObject(postmasterProcess, 0) == WAIT_OBJECT_0)
+
+       /*
+        * If we've been able to identify the child postmaster's PID, check
+        * the process is still alive.  This covers cases where the postmaster
+        * successfully created the pidfile but then crashed without removing
+        * it.
+        */
+       if (pm_pid > 0 && !postmaster_is_alive((pid_t) pm_pid))
            return PQPING_NO_RESPONSE;
-#endif
 
        /* No response, or startup still in process; wait */
 #if defined(WIN32)
@@ -846,7 +816,7 @@ static void
 do_start(void)
 {
    pgpid_t     old_pid = 0;
-   pgpid_t     pm_pid;
+   int         exitcode;
 
    if (ctl_command != RESTART_COMMAND)
    {
@@ -886,13 +856,19 @@ do_start(void)
    }
 #endif
 
-   pm_pid = start_postmaster();
+   exitcode = start_postmaster();
+   if (exitcode != 0)
+   {
+       write_stderr(_("%s: could not start server: exit code was %d\n"),
+                    progname, exitcode);
+       exit(1);
+   }
 
    if (do_wait)
    {
        print_msg(_("waiting for server to start..."));
 
-       switch (test_postmaster_connection(pm_pid, false))
+       switch (test_postmaster_connection(false))
        {
            case PQPING_OK:
                print_msg(_(" done\n"));
@@ -918,12 +894,6 @@ do_start(void)
    }
    else
        print_msg(_("server starting\n"));
-
-#ifdef WIN32
-   /* Now we don't need the handle to the shell process anymore */
-   CloseHandle(postmasterProcess);
-   postmasterProcess = INVALID_HANDLE_VALUE;
-#endif
 }
 
 
@@ -1528,7 +1498,7 @@ pgwin32_ServiceMain(DWORD argc, LPTSTR *argv)
    if (do_wait)
    {
        write_eventlog(EVENTLOG_INFORMATION_TYPE, _("Waiting for server startup...\n"));
-       if (test_postmaster_connection(postmasterPID, true) != PQPING_OK)
+       if (test_postmaster_connection(true) != PQPING_OK)
        {
            write_eventlog(EVENTLOG_ERROR_TYPE, _("Timed out waiting for server startup\n"));
            pgwin32_SetServiceStatus(SERVICE_STOPPED);
@@ -1555,9 +1525,10 @@ pgwin32_ServiceMain(DWORD argc, LPTSTR *argv)
            {
                /*
                 * status.dwCheckPoint can be incremented by
-                * test_postmaster_connection(), so it might not start from 0.
+                * test_postmaster_connection(true), so it might not
+                * start from 0.
                 */
-               int         maxShutdownCheckPoint = status.dwCheckPoint + 12;
+               int maxShutdownCheckPoint = status.dwCheckPoint + 12;;
 
                kill(postmasterPID, SIGINT);