Thread

1. Small Bug in pgstat display during recovery conflict resolution

   Andres Freund <andres@anarazel.de> — 2010-02-07T20:47:39Z

   Hi Simon, Hi all,
   
   
   if (!logged && (wait_s > 0 || wait_us > 500000))
   {
           const char *oldactivitymsg;
           int                     len;
   
           oldactivitymsg = get_ps_display(&len);
           snprintf(waitactivitymsg, sizeof(waitactivitymsg),
                            "waiting for max_standby_delay (%u s)",
                            MaxStandbyDelay);
           set_ps_display(waitactivitymsg, false);
           if (len > 100)
                   len = 100;
           memcpy(waitactivitymsg, oldactivitymsg, len);
   
           pgstat_report_waiting(true);
   
           logged = true;
   }
   ..
   if (logged)
   {
           set_ps_display(waitactivitymsg, false);
           pgstat_report_waiting(false);
   }
   
   That doesnt work because get_ps_display returns the internal buffer. This 
   leads to the situation that after conflict resolution the 
   "waiting for max_standby_delay ..."
   message is displayed until the next segment starts where its replaced
   again by the 
   "... recovering ..." line.
   
   Additionally the old code may print unintialized memory if get_ps_display
    returns a string without a \0 terminator.
   
   The attached patch fixes that.
   
   Andres
   

2. Re: Small Bug in pgstat display during recovery conflict resolution

   Simon Riggs <simon@2ndquadrant.com> — 2010-02-13T16:30:36Z

   Committed, thanks.
   
   On Sun, 2010-02-07 at 21:47 +0100, Andres Freund wrote:
   > Hi Simon, Hi all,
   > 
   > 
   > if (!logged && (wait_s > 0 || wait_us > 500000))
   > {
   >         const char *oldactivitymsg;
   >         int                     len;
   > 
   >         oldactivitymsg = get_ps_display(&len);
   >         snprintf(waitactivitymsg, sizeof(waitactivitymsg),
   >                          "waiting for max_standby_delay (%u s)",
   >                          MaxStandbyDelay);
   >         set_ps_display(waitactivitymsg, false);
   >         if (len > 100)
   >                 len = 100;
   >         memcpy(waitactivitymsg, oldactivitymsg, len);
   > 
   >         pgstat_report_waiting(true);
   > 
   >         logged = true;
   > }
   > ..
   > if (logged)
   > {
   >         set_ps_display(waitactivitymsg, false);
   >         pgstat_report_waiting(false);
   > }
   > 
   > That doesnt work because get_ps_display returns the internal buffer. This 
   > leads to the situation that after conflict resolution the 
   > "waiting for max_standby_delay ..."
   > message is displayed until the next segment starts where its replaced
   > again by the 
   > "... recovering ..." line.
   > 
   > Additionally the old code may print unintialized memory if get_ps_display
   >  returns a string without a \0 terminator.
   > 
   > The attached patch fixes that.
   > 
   > Andres
   -- 
    Simon Riggs           www.2ndQuadrant.com