Fix for BUG#13023: "SQL Thread is up but doesn't move forward". Details in slave.cc;

in short we now record whenever the slave I/O thread ignores a master's event because of its server id,
and use this info in the slave SQL thread to advance Exec_master_log_pos. Because if we
do not, this variable stays at the position of the last executed event, i.e. the last *non-ignored*
executed one, which may not be the last of the master's binlog (and so the slave *looks* behind
the master though it's data-wise it's not).


mysql-test/t/rpl_dual_pos_advance-master.opt:
  empty; its goal is just to trigger a server restart after running the test,
  so that the master forgets that it was a slave (otherwise it affects the following tests).
sql/log.cc:
  No more default arguments for Rotate_log_event constructor.
  MYSQL_LOG::appendv() is now called without mutex.
sql/log_event.cc:
  Moving one Rotate_log_event constructor from log_event.h. Support for on-demand choice of
  duplicating the string argument of the constructor or not (because there now are needs for both
  alternatives, see slave.cc).
sql/log_event.h:
  We now have a case where a Rotate_log_event is executed by the slave SQL thread while
  not being in the relay log, so it needs to pretend its length is 0: a ZERO_LEN flag for that;
  a flag DUP_NAME (replaces "bool alloced") to be able to choose if we want the constructor
  to duplicate the string argument or not.
sql/slave.cc:
  A comment for BUG#13861 (to be fixed). llstr() instead of %ld as the number is ulonglong.
  mi->rli becomes rli in some places.
  Fix for BUG#13023:
  - in the slave I/O thread, whenever we ignore an event because of its server id we update
  a couple of coordinates in memory
  - in the slave SQL thread, whenever we bump into the end of the latest relay log, we check
  this couple of coordinates to see if we should advance our Exec_master_log_pos.
  - when the slave I/O thread terminates it saves these in-memory coordinates into a Rotate event
  in the relay log, so that they are durable.
sql/slave.h:
  A couple of coordinates in RELAY_LOG_INFO to keep track of the last ignored events received
  by the slave I/O thread (ignored because of the server id).
mysql-test/r/rpl_dual_pos_advance.result:
  New BitKeeper file ``mysql-test/r/rpl_dual_pos_advance.result''
mysql-test/t/rpl_dual_pos_advance.test:
  Test for BUG#13023 (with a part, disabled, to test BUG#13861 when I fix it).
  Before the fix, this test used to hang.

mysql-test/r/rpl_dual_pos_advance.result

+stop slave;
+drop table if exists t1,t2,t3,t4,t5,t6,t7,t8,t9;
+reset master;
+reset slave;
+drop table if exists t1,t2,t3,t4,t5,t6,t7,t8,t9;
+start slave;
+reset master;
+change master to master_host="127.0.0.1",master_port=SLAVE_PORT,master_user="root";
+start slave;
+create table t1 (n int);
+create table t4 (n int);
+create table t5 (n int);
+create table t6 (n int);
+show tables;
+Tables_in_test
+t1
+t4
+t5
+t6
+stop slave;
+reset slave;
+drop table t1,t4,t5,t6;

mysql-test/t/rpl_dual_pos_advance.test

+# This test checks that in a dual-head setup
+# A->B->A, where A has --log-slave-updates (why would it?
+# assume that there is a C as slave of A),
+# then the Exec_master_log_pos of SHOW SLAVE STATUS does
+# not stay too low on B(BUG#13023 due to events ignored because
+# of their server id).
+# It also will test BUG#13861.
+
+source include/master-slave.inc;
+
+
+# set up "dual head"
+
+connection slave;
+reset master;
+
+connection master;
+--replace_result $SLAVE_MYPORT SLAVE_PORT
+eval change master to master_host="127.0.0.1",master_port=$SLAVE_MYPORT,master_user="root";
+
+start slave;
+
+# now we test it
+
+connection slave;
+
+create table t1 (n int);
+
+save_master_pos;
+connection master;
+sync_with_master;
+
+# Now test BUG#13861. This will be enabled when Guilhem fixes this
+# bug.
+
+# stop slave
+
+# create table t2 (n int); # create one ignored event
+
+# save_master_pos;
+# connection slave;
+# sync_with_master;
+
+# connection slave;
+
+# show tables;
+
+# save_master_pos;
+
+# create table t3 (n int);
+
+# connection master;
+
+# bug is that START SLAVE UNTIL may stop too late, we test that by
+# asking it to stop before creation of t3.
+
+# start slave until master_log_file="slave-bin.000001",master_log_pos=195;
+
+# wait until it's started (the position below is the start of "CREATE
+# TABLE t2") (otherwise wait_for_slave_to_stop may return at once)
+
+# select master_pos_wait("slave-bin.000001",137);
+
+# wait_for_slave_to_stop;
+
+# then BUG#13861 causes t3 to show up below (because stopped too
+# late).
+
+# show tables;
+
+# start slave;
+
+# BUG#13023 is that Exec_master_log_pos may stay too low "forever":
+
+connection master;
+
+create table t4 (n int); # create 3 ignored events
+create table t5 (n int);
+create table t6 (n int);
+
+save_master_pos;
+connection slave;
+sync_with_master;
+
+connection slave;
+
+save_master_pos;
+
+connection master;
+
+# then BUG#13023 caused hang below ("master" looks behind, while it's
+# not in terms of updates done).
+
+sync_with_master;
+
+show tables;
+
+# cleanup
+
+stop slave;
+reset slave;
+drop table t1,t4,t5,t6; # add t2 and t3 later
+
+save_master_pos;
+connection slave;
+sync_with_master;
+
+# End of 4.1 tests

sql/log.cc

@@ -1028,7 +1028,8 @@ void MYSQL_LOG::new_file(bool need_lock)
         to change base names at some point.
       */
       THD *thd = current_thd; /* may be 0 if we are reacting to SIGHUP */
-      Rotate_log_event r(thd,new_name+dirname_length(new_name));
+      Rotate_log_event r(thd,new_name+dirname_length(new_name),
+                         0, LOG_EVENT_OFFSET, 0);
       r.set_log_pos(this);
       r.write(&log_file);
       bytes_written += r.get_event_len();
@@ -1106,7 +1107,7 @@ bool MYSQL_LOG::appendv(const char* buf, uint len,...)
   
   DBUG_ASSERT(log_file.type == SEQ_READ_APPEND);
   
-  pthread_mutex_lock(&LOCK_log);
+  safe_mutex_assert_owner(&LOCK_log);
   do
   {
     if (my_b_append(&log_file,(byte*) buf,len))
@@ -1125,7 +1126,6 @@ bool MYSQL_LOG::appendv(const char* buf, uint len,...)
   }
 
 err:
-  pthread_mutex_unlock(&LOCK_log);
   if (!error)
     signal_update();
   DBUG_RETURN(error);

sql/log_event.cc

@@ -2013,18 +2013,44 @@ void Rotate_log_event::print(FILE* file, bool short_form, char* last_db)
 #endif /* MYSQL_CLIENT */
 
 
+
 /*
-  Rotate_log_event::Rotate_log_event()
+  Rotate_log_event::Rotate_log_event() (2 constructors)
 */
 
+
+#ifndef MYSQL_CLIENT
+Rotate_log_event::Rotate_log_event(THD* thd_arg,
+                                   const char* new_log_ident_arg,
+                                   uint ident_len_arg, ulonglong pos_arg,
+                                   uint flags_arg)
+  :Log_event(), new_log_ident(new_log_ident_arg),
+   pos(pos_arg),ident_len(ident_len_arg ? ident_len_arg :
+                          (uint) strlen(new_log_ident_arg)), flags(flags_arg)
+{
+#ifndef DBUG_OFF
+  char buff[22];
+  DBUG_ENTER("Rotate_log_event::Rotate_log_event(THD*,...)");
+  DBUG_PRINT("enter",("new_log_ident %s pos %s flags %lu", new_log_ident_arg,
+                      llstr(pos_arg, buff), flags));
+#endif
+  if (flags & DUP_NAME)
+    new_log_ident= my_strdup_with_length(new_log_ident_arg,
+                                         ident_len,
+                                         MYF(MY_WME));
+  DBUG_VOID_RETURN;
+}
+#endif
+
+
 Rotate_log_event::Rotate_log_event(const char* buf, int event_len,
 				   bool old_format)
-  :Log_event(buf, old_format),new_log_ident(NULL),alloced(0)
+  :Log_event(buf, old_format), new_log_ident(0), flags(DUP_NAME)
 {
   // The caller will ensure that event_len is what we have at EVENT_LEN_OFFSET
   int header_size = (old_format) ? OLD_HEADER_LEN : LOG_EVENT_HEADER_LEN;
   uint ident_offset;
-  DBUG_ENTER("Rotate_log_event");
+  DBUG_ENTER("Rotate_log_event::Rotate_log_event(char*,...)");
 
   if (event_len < header_size)
     DBUG_VOID_RETURN;
@@ -2043,12 +2069,9 @@ Rotate_log_event::Rotate_log_event(const char* buf, int event_len,
     ident_offset = ROTATE_HEADER_LEN;
   }
   set_if_smaller(ident_len,FN_REFLEN-1);
-  if (!(new_log_ident= my_strdup_with_length((byte*) buf +
-					     ident_offset,
+  new_log_ident= my_strdup_with_length((byte*) buf + ident_offset,
                                        (uint) ident_len,
-					     MYF(MY_WME))))
-    DBUG_VOID_RETURN;
-  alloced = 1;
+                                       MYF(MY_WME));
   DBUG_VOID_RETURN;
 }
 
@@ -2060,6 +2083,7 @@ Rotate_log_event::Rotate_log_event(const char* buf, int event_len,
 int Rotate_log_event::write_data(IO_CACHE* file)
 {
   char buf[ROTATE_HEADER_LEN];
+  DBUG_ASSERT(!(flags & ZERO_LEN)); // such an event cannot be written
   int8store(buf + R_POS_OFFSET, pos);
   return (my_b_safe_write(file, (byte*)buf, ROTATE_HEADER_LEN) ||
 	  my_b_safe_write(file, (byte*)new_log_ident, (uint) ident_len));

sql/log_event.h

@@ -434,7 +434,7 @@ public:
   }
   virtual int get_data_size() { return 0;}
   virtual int get_data_body_offset() { return 0; }
-  int get_event_len()
+  virtual int get_event_len()
   {
     return (cached_event_len ? cached_event_len :
 	    (cached_event_len = LOG_EVENT_HEADER_LEN + get_data_size()));
@@ -849,18 +849,18 @@ public:
 class Rotate_log_event: public Log_event
 {
 public:
+  enum {
+    ZERO_LEN= 1, // if event should report 0 as its length
+    DUP_NAME= 2 // if constructor should dup the string argument
+  };
   const char* new_log_ident;
   ulonglong pos;
   uint ident_len;
-  bool alloced;
+  uint flags;
 #ifndef MYSQL_CLIENT  
   Rotate_log_event(THD* thd_arg, const char* new_log_ident_arg,
-		   uint ident_len_arg = 0,
-		   ulonglong pos_arg = LOG_EVENT_OFFSET)
-    :Log_event(), new_log_ident(new_log_ident_arg),
-    pos(pos_arg),ident_len(ident_len_arg ? ident_len_arg :
-			   (uint) strlen(new_log_ident_arg)), alloced(0)
-  {}
+		   uint ident_len_arg,
+		   ulonglong pos_arg, uint flags);
 #ifdef HAVE_REPLICATION
   void pack_info(Protocol* protocol);
   int exec_event(struct st_relay_log_info* rli);
@@ -872,10 +872,18 @@ public:
   Rotate_log_event(const char* buf, int event_len, bool old_format);
   ~Rotate_log_event()
   {
-    if (alloced)
-      my_free((gptr) new_log_ident, MYF(0));
+    if (flags & DUP_NAME)
+      my_free((gptr) new_log_ident, MYF(MY_ALLOW_ZERO_PTR));
   }
   Log_event_type get_type_code() { return ROTATE_EVENT;}
+  virtual int get_event_len()
+  {
+    if (flags & ZERO_LEN)
+      return 0;
+    if (cached_event_len == 0)
+      cached_event_len= LOG_EVENT_HEADER_LEN + get_data_size();
+    return cached_event_len;
+  }
   int get_data_size() { return  ident_len + ROTATE_HEADER_LEN;}
   bool is_valid() { return new_log_ident != 0; }
   int write_data(IO_CACHE* file);

sql/slave.cc

@@ -1739,6 +1739,55 @@ static int count_relay_log_space(RELAY_LOG_INFO* rli)
 }
 
 
+/*
+  Builds a Rotate from the ignored events' info and writes it to relay log.
+
+  SYNOPSIS
+  write_ignored_events_info_to_relay_log()
+    thd             pointer to I/O thread's thd
+    mi
+
+  DESCRIPTION
+    Slave I/O thread, going to die, must leave a durable trace of the
+    ignored events' end position for the use of the slave SQL thread, by
+    calling this function. Only that thread can call it (see assertion).
+ */
+static void write_ignored_events_info_to_relay_log(THD *thd, MASTER_INFO *mi)
+{
+  RELAY_LOG_INFO *rli= &mi->rli;
+  pthread_mutex_t *log_lock= rli->relay_log.get_log_lock();
+  DBUG_ASSERT(thd == mi->io_thd);
+  pthread_mutex_lock(log_lock);
+  if (rli->ign_master_log_name_end[0])
+  {
+    DBUG_PRINT("info",("writing a Rotate event to track down ignored events"));
+    Rotate_log_event *ev= new Rotate_log_event(thd, rli->ign_master_log_name_end,
+                                               0, rli->ign_master_log_pos_end,
+                                               Rotate_log_event::DUP_NAME);
+    rli->ign_master_log_name_end[0]= 0;
+    /* can unlock before writing as slave SQL thd will soon see our Rotate */
+    pthread_mutex_unlock(log_lock);
+    if (likely((bool)ev))
+    {
+      ev->server_id= 0; // don't be ignored by slave SQL thread
+      if (unlikely(rli->relay_log.append(ev)))
+        sql_print_error("Slave I/O thread failed to write a Rotate event"
+                        " to the relay log, "
+                        "SHOW SLAVE STATUS may be inaccurate");
+      rli->relay_log.harvest_bytes_written(&rli->log_space_total);
+      flush_master_info(mi, 1);
+      delete ev;
+    }
+    else
+      sql_print_error("Slave I/O thread failed to create a Rotate event"
+                      " (out of memory?), "
+                      "SHOW SLAVE STATUS may be inaccurate");
+  }
+  else
+    pthread_mutex_unlock(log_lock);
+}
+
+
 void init_master_info_with_options(MASTER_INFO* mi)
 {
   mi->master_log_name[0] = 0;
@@ -2334,7 +2383,7 @@ st_relay_log_info::st_relay_log_info()
 {
   group_relay_log_name[0]= event_relay_log_name[0]=
     group_master_log_name[0]= 0;
-  last_slave_error[0]=0; until_log_name[0]= 0;
+  last_slave_error[0]= until_log_name[0]= ign_master_log_name_end[0]= 0;
 
   bzero((char*) &info_file, sizeof(info_file));
   bzero((char*) &cache_buf, sizeof(cache_buf));
@@ -2886,11 +2935,20 @@ static int exec_relay_log_event(THD* thd, RELAY_LOG_INFO* rli)
    */
   pthread_mutex_lock(&rli->data_lock);
   
+  /*
+    This tests if the position of the end of the last previous executed event
+    hits the UNTIL barrier.
+    We would prefer to test if the position of the start (or possibly) end of
+    the to-be-read event hits the UNTIL barrier, this is different if there
+    was an event ignored by the I/O thread just before (BUG#13861 to be
+    fixed).
+  */
   if (rli->until_condition!=RELAY_LOG_INFO::UNTIL_NONE && 
       rli->is_until_satisfied()) 
   {
+    char buf[22];
     sql_print_error("Slave SQL thread stopped because it reached its"
-                    " UNTIL position %ld", (long) rli->until_pos());
+                    " UNTIL position %s", llstr(rli->until_pos(), buf));
     /* 
       Setting abort_slave flag because we do not want additional message about
       error in query execution to be printed.
@@ -2925,7 +2983,6 @@ static int exec_relay_log_event(THD* thd, RELAY_LOG_INFO* rli)
     if ((ev->server_id == (uint32) ::server_id && !replicate_same_server_id) ||
 	(rli->slave_skip_counter && type_code != ROTATE_EVENT))
     {
-      /* TODO: I/O thread should not even log events with the same server id */
       rli->inc_group_relay_log_pos(ev->get_event_len(),
 		   type_code != STOP_EVENT ? ev->log_pos : LL(0),
 		   1/* skip lock*/);
@@ -3034,6 +3091,7 @@ extern "C" pthread_handler_decl(handle_slave_io,arg)
   THD *thd; // needs to be first for thread_stack
   MYSQL *mysql;
   MASTER_INFO *mi = (MASTER_INFO*)arg;
+  RELAY_LOG_INFO *rli= &mi->rli;
   char llbuff[22];
   uint retry_count;
   
@@ -3276,16 +3334,16 @@ reconnect done to recover from failed read");
         char llbuf1[22], llbuf2[22];
         DBUG_PRINT("info", ("log_space_limit=%s log_space_total=%s \
 ignore_log_space_limit=%d",
-                            llstr(mi->rli.log_space_limit,llbuf1),
-                            llstr(mi->rli.log_space_total,llbuf2),
-                            (int) mi->rli.ignore_log_space_limit)); 
+                            llstr(rli->log_space_limit,llbuf1),
+                            llstr(rli->log_space_total,llbuf2),
+                            (int) rli->ignore_log_space_limit)); 
       }
 #endif
 
-      if (mi->rli.log_space_limit && mi->rli.log_space_limit <
-	  mi->rli.log_space_total &&
-          !mi->rli.ignore_log_space_limit)
-	if (wait_for_relay_log_space(&mi->rli))
+      if (rli->log_space_limit && rli->log_space_limit <
+	  rli->log_space_total &&
+          !rli->ignore_log_space_limit)
+	if (wait_for_relay_log_space(rli))
 	{
 	  sql_print_error("Slave I/O thread aborted while waiting for relay \
 log space");
@@ -3316,6 +3374,7 @@ err:
     mysql_close(mysql);
     mi->mysql=0;
   }
+  write_ignored_events_info_to_relay_log(thd, mi);
   thd->proc_info = "Waiting for slave mutex on exit";
   pthread_mutex_lock(&mi->run_lock);
   mi->slave_running = 0;
@@ -3668,6 +3727,7 @@ static int process_io_rotate(MASTER_INFO *mi, Rotate_log_event *rev)
   if (unlikely(!rev->is_valid()))
     DBUG_RETURN(1);
 
+  /* Safe copy as 'rev' has been "sanitized" in Rotate_log_event's ctor */
   memcpy(mi->master_log_name, rev->new_log_ident, rev->ident_len+1);
   mi->master_log_pos= rev->pos;
   DBUG_PRINT("info", ("master_log_pos: '%s' %d",
@@ -3813,6 +3873,7 @@ int queue_event(MASTER_INFO* mi,const char* buf, ulong event_len)
   int error= 0;
   ulong inc_pos;
   RELAY_LOG_INFO *rli= &mi->rli;
+  pthread_mutex_t *log_lock= rli->relay_log.get_log_lock();
   DBUG_ENTER("queue_event");
 
   if (mi->old_format)
@@ -3820,11 +3881,6 @@ int queue_event(MASTER_INFO* mi,const char* buf, ulong event_len)
 
   pthread_mutex_lock(&mi->data_lock);
 
-  /*
-    TODO: figure out if other events in addition to Rotate
-    require special processing.
-    Guilhem 2003-06 : I don't think so.
-  */
   switch (buf[EVENT_TYPE_OFFSET]) {
   case STOP_EVENT:
     /*
@@ -3873,16 +3929,27 @@ int queue_event(MASTER_INFO* mi,const char* buf, ulong event_len)
      direct master (an unsupported, useless setup!).
   */
 
+  pthread_mutex_lock(log_lock);
+
   if ((uint4korr(buf + SERVER_ID_OFFSET) == ::server_id) &&
       !replicate_same_server_id)
   {
     /*
       Do not write it to the relay log.
-      We still want to increment, so that we won't re-read this event from the
-      master if the slave IO thread is now stopped/restarted (more efficient if
-      the events we are ignoring are big LOAD DATA INFILE).
+      a) We still want to increment mi->master_log_pos, so that we won't
+      re-read this event from the master if the slave IO thread is now
+      stopped/restarted (more efficient if the events we are ignoring are big
+      LOAD DATA INFILE).
+      b) We want to record that we are skipping events, for the information of
+      the slave SQL thread, otherwise that thread may let
+      rli->group_relay_log_pos stay too small if the last binlog's event is
+      ignored.
     */
     mi->master_log_pos+= inc_pos;
+    memcpy(rli->ign_master_log_name_end, mi->master_log_name, FN_REFLEN);
+    DBUG_ASSERT(rli->ign_master_log_name_end[0]);
+    rli->ign_master_log_pos_end= mi->master_log_pos;
+    rli->relay_log.signal_update(); // the slave SQL thread needs to re-check
     DBUG_PRINT("info", ("master_log_pos: %d, event originating from the same server, ignored", (ulong) mi->master_log_pos));
   }  
   else
@@ -3894,7 +3961,9 @@ int queue_event(MASTER_INFO* mi,const char* buf, ulong event_len)
       DBUG_PRINT("info", ("master_log_pos: %d", (ulong) mi->master_log_pos));
       rli->relay_log.harvest_bytes_written(&rli->log_space_total);
     }
+    rli->ign_master_log_name_end[0]= 0; // last event is not ignored
   }
+  pthread_mutex_unlock(log_lock);
 
 err:
   pthread_mutex_unlock(&mi->data_lock);
@@ -4262,6 +4331,27 @@ Before assert, my_b_tell(cur_log)=%s  rli->event_relay_log_pos=%s",
         rli->last_master_timestamp= 0;
 
 	DBUG_ASSERT(rli->relay_log.get_open_count() == rli->cur_log_old_open_count);
+
+        if (rli->ign_master_log_name_end[0])
+        {
+          /* We generate and return a Rotate, to make our positions advance */
+          DBUG_PRINT("info",("seeing an ignored end segment"));
+          ev= new Rotate_log_event(thd, rli->ign_master_log_name_end,
+                                   0, rli->ign_master_log_pos_end,
+                                   Rotate_log_event::DUP_NAME |
+                                   Rotate_log_event::ZERO_LEN);
+          rli->ign_master_log_name_end[0]= 0;
+          if (unlikely(!ev))
+          {
+            errmsg= "Slave SQL thread failed to create a Rotate event "
+              "(out of memory?), SHOW SLAVE STATUS may be inaccurate";
+            goto err;
+          }
+          pthread_mutex_unlock(log_lock);
+          ev->server_id= 0; // don't be ignored by slave SQL thread
+          DBUG_RETURN(ev);
+        }
+
 	/*
 	  We can, and should release data_lock while we are waiting for
 	  update. If we do not, show slave status will block

sql/slave.h

@@ -304,6 +304,17 @@ typedef struct st_relay_log_info
   */
   ulong trans_retries, retried_trans;
 
+  /*
+    If the end of the hot relay log is made of master's events ignored by the
+    slave I/O thread, these two keep track of the coords (in the master's
+    binlog) of the last of these events seen by the slave I/O thread. If not,
+    ign_master_log_name_end[0] == 0.
+    As they are like a Rotate event read/written from/to the relay log, they
+    are both protected by rli->relay_log.LOCK_log.
+  */
+  char ign_master_log_name_end[FN_REFLEN];
+  ulonglong ign_master_log_pos_end;
+
   st_relay_log_info();
   ~st_relay_log_info();