More error messages. This is intended to help debugging; presently I have a

support issue with an unclear message which can have N reasons for appearing.
This should help us know at which point it failed, and get the errno when
my_open was involved (as the reason for the unclear message is often a
permission problem).
RESET SLAVE resets last_error and last_errno in SHOW SLAVE STATUS (without this,
rpl_loaddata.test, which is expected to generate an error in last_error, influenced
rpl_log_pos.test).
A small test update.
Added STOP SLAVE to mysql-test-run to get rid of several stupid error messages
which are printed while the master restarts and the slave attempts/manages to
connect to it and sends it nonsense binlog requests.

mysql-test/mysql-test-run.sh

@@ -1064,6 +1064,16 @@ stop_slave ()
   fi
 }
 
+stop_slave_threads ()
+{
+  eval "this_slave_running=\$SLAVE$1_RUNNING"
+  slave_ident="slave$1"
+  if [ x$this_slave_running = x1 ]
+  then
+    $MYSQLADMIN --no-defaults -uroot --socket=$MYSQL_TMP_DIR/$slave_ident.sock stop-slave > /dev/null 2>&1
+  fi
+}
+
 stop_master ()
 {
   if [ x$MASTER_RUNNING = x1 ]
@@ -1157,6 +1167,12 @@ run_testcase ()
    return
  fi
 
+ # Stop all slave threads, so that we don't have useless reconnection attempts
+ # and error messages in case the slave and master servers restart.
+ stop_slave_threads
+ stop_slave_threads 1
+ stop_slave_threads 2
+
  if [ -z "$USE_RUNNING_SERVER" ] ;
  then
    if [ -f $master_opt_file ] ;

mysql-test/r/rpl000018.result

+reset master;
 reset slave;
 slave start;
 show master logs;

mysql-test/t/rpl000018.test

@@ -6,6 +6,8 @@
 require_manager;
 connect (master,localhost,root,,test,0,master.sock);
 connect (slave,localhost,root,,test,0,slave.sock);
+connection master;
+reset master;
 server_stop master;
 server_start master;
 connection slave;

sql/slave.cc

@@ -115,6 +115,8 @@ int init_slave()
 {
   DBUG_ENTER("init_slave");
 
+  /* This is called when mysqld starts */
+
   /*
     TODO: re-write this to interate through the list of files
     for multi-master
@@ -126,11 +128,16 @@ int init_slave()
     If master_host is specified, create the master_info file if it doesn't
     exists.
   */
-  if (!active_mi ||
-      init_master_info(active_mi,master_info_file,relay_log_info_file,
+  if (!active_mi)
+  {
+    sql_print_error("Failed to allocate memory for the master info structure");
+    goto err;
+  }
+    
+  if(init_master_info(active_mi,master_info_file,relay_log_info_file,
 		       !master_host))
   {
-    sql_print_error("Note: Failed to initialized master info");
+    sql_print_error("Failed to initialize the master info structure");
     goto err;
   }
 
@@ -150,7 +157,7 @@ int init_slave()
 			    relay_log_info_file,
 			    SLAVE_IO | SLAVE_SQL))
     {
-      sql_print_error("Warning: Can't create threads to handle slave");
+      sql_print_error("Failed to create slave threads");
       goto err;
     }
   }
@@ -1226,7 +1233,10 @@ int init_relay_log_info(RELAY_LOG_INFO* rli, const char* info_fname)
 	       "-relay-bin", opt_relaylog_index_name,
 	       LOG_BIN, 1 /* read_append cache */,
 	       1 /* no auto events */))
+  {
+    sql_print_error("Failed in open_log() called from init_relay_log_info()");
     DBUG_RETURN(1);
+  }
 
   /* if file does not exist */
   if (access(fname,F_OK))
@@ -1237,10 +1247,18 @@ int init_relay_log_info(RELAY_LOG_INFO* rli, const char* info_fname)
     */
     if (info_fd >= 0)
       my_close(info_fd, MYF(MY_WME));
-    if ((info_fd = my_open(fname, O_CREAT|O_RDWR|O_BINARY, MYF(MY_WME))) < 0 ||
-	init_io_cache(&rli->info_file, info_fd, IO_SIZE*2, READ_CACHE, 0L,0,
+    if ((info_fd = my_open(fname, O_CREAT|O_RDWR|O_BINARY, MYF(MY_WME))) < 0)
+    {
+      sql_print_error("Failed to create a new relay log info file (\
+file '%s', errno %d)", fname, my_errno);
+      msg= current_thd->net.last_error;
+      goto err;
+    }
+    if (init_io_cache(&rli->info_file, info_fd, IO_SIZE*2, READ_CACHE, 0L,0,
 		      MYF(MY_WME))) 
     {
+      sql_print_error("Failed to create a cache on relay log info file (\
+file '%s')", fname);
       msg= current_thd->net.last_error;
       goto err;
     }
@@ -1248,7 +1266,11 @@ int init_relay_log_info(RELAY_LOG_INFO* rli, const char* info_fname)
     /* Init relay log with first entry in the relay index file */
     if (init_relay_log_pos(rli,NullS,BIN_LOG_HEADER_SIZE,0 /* no data lock */,
 			   &msg))
+    {
+      sql_print_error("Failed to open the relay log (relay_log_name='FIRST', \
+relay_log_pos=4");
       goto err;
+    }
     rli->master_log_name[0]= 0;
     rli->master_log_pos= 0;		
     rli->info_fd= info_fd;
@@ -1257,9 +1279,23 @@ int init_relay_log_info(RELAY_LOG_INFO* rli, const char* info_fname)
   {
     if (info_fd >= 0)
       reinit_io_cache(&rli->info_file, READ_CACHE, 0L,0,0);
-    else if ((info_fd = my_open(fname, O_RDWR|O_BINARY, MYF(MY_WME))) < 0 ||
-	     init_io_cache(&rli->info_file, info_fd,
+    else 
+    {
+      int error=0;
+      if ((info_fd = my_open(fname, O_RDWR|O_BINARY, MYF(MY_WME))) < 0)
+      {
+        sql_print_error("Failed to open the existing relay log info file (\
+file '%s', errno %d)", fname, my_errno);
+        error= 1;
+      }
+      else if (init_io_cache(&rli->info_file, info_fd,
                              IO_SIZE*2, READ_CACHE, 0L, 0, MYF(MY_WME)))
+      {
+        sql_print_error("Failed to create a cache on relay log info file (\
+file '%s')", fname);
+        error= 1;
+      }
+      if (error)
       {
         if (info_fd >= 0)
           my_close(info_fd, MYF(0));
@@ -1268,6 +1304,7 @@ int init_relay_log_info(RELAY_LOG_INFO* rli, const char* info_fname)
         pthread_mutex_unlock(&rli->data_lock);
         DBUG_RETURN(1);
       }
+    }
          
     rli->info_fd = info_fd;
     int relay_log_pos, master_log_pos;
@@ -1292,8 +1329,13 @@ int init_relay_log_info(RELAY_LOG_INFO* rli, const char* info_fname)
 			   rli->relay_log_pos,
 			   0 /* no data lock*/,
 			   &msg))
+    {
+      char llbuf[22];
+      sql_print_error("Failed to open the relay log (relay_log_name='%s', \
+relay_log_pos=%s", rli->relay_log_name, llstr(rli->relay_log_pos, llbuf));
       goto err;
     }
+  }
   DBUG_ASSERT(rli->relay_log_pos >= BIN_LOG_HEADER_SIZE);
   DBUG_ASSERT(my_b_tell(rli->cur_log) == rli->relay_log_pos);
   /*
@@ -1301,7 +1343,8 @@ int init_relay_log_info(RELAY_LOG_INFO* rli, const char* info_fname)
     before flush_relay_log_info
   */
   reinit_io_cache(&rli->info_file, WRITE_CACHE,0L,0,1);
-  error= flush_relay_log_info(rli);
+  if ((error= flush_relay_log_info(rli)))
+    sql_print_error("Failed to flush relay log info file");
   if (count_relay_log_space(rli))
   {
     msg="Error counting relay log space";
@@ -1405,6 +1448,8 @@ int init_master_info(MASTER_INFO* mi, const char* master_info_fname,
   pthread_mutex_lock(&mi->data_lock);
   fd = mi->fd;
 
+  /* does master.info exist ? */
+  
   if (access(fname,F_OK))
   {
     if (abort_if_no_master_info_file)
@@ -1418,10 +1463,19 @@ int init_master_info(MASTER_INFO* mi, const char* master_info_fname,
     */
     if (fd >= 0)
       my_close(fd, MYF(MY_WME));
-    if ((fd = my_open(fname, O_CREAT|O_RDWR|O_BINARY, MYF(MY_WME))) < 0 ||
-	init_io_cache(&mi->file, fd, IO_SIZE*2, READ_CACHE, 0L,0,
+    if ((fd = my_open(fname, O_CREAT|O_RDWR|O_BINARY, MYF(MY_WME))) < 0 )
+    {
+      sql_print_error("Failed to create a new master info file (\
+file '%s', errno %d)", fname, my_errno);
+      goto err;
+    }
+    if (init_io_cache(&mi->file, fd, IO_SIZE*2, READ_CACHE, 0L,0,
 		      MYF(MY_WME)))
+    {
+      sql_print_error("Failed to create a cache on master info file (\
+file '%s')", fname);
       goto err;
+    }
 
     mi->master_log_name[0] = 0;
     mi->master_log_pos = BIN_LOG_HEADER_SIZE;		// skip magic number
@@ -1440,10 +1494,22 @@ int init_master_info(MASTER_INFO* mi, const char* master_info_fname,
   {
     if (fd >= 0)
       reinit_io_cache(&mi->file, READ_CACHE, 0L,0,0);
-    else if ((fd = my_open(fname, O_RDWR|O_BINARY, MYF(MY_WME))) < 0 ||
-	     init_io_cache(&mi->file, fd, IO_SIZE*2, READ_CACHE, 0L,
+    else 
+    {
+      if ((fd = my_open(fname, O_RDWR|O_BINARY, MYF(MY_WME))) < 0 )
+      {
+        sql_print_error("Failed to open the existing master info file (\
+file '%s', errno %d)", fname, my_errno);
+        goto err;
+      }
+      if (init_io_cache(&mi->file, fd, IO_SIZE*2, READ_CACHE, 0L,
                         0, MYF(MY_WME)))
+      {
+        sql_print_error("Failed to create a cache on master info file (\
+file '%s')", fname);
         goto err;
+      }
+    }
 
     mi->fd = fd;
     int port, connect_retry, master_log_pos;
@@ -1484,7 +1550,8 @@ int init_master_info(MASTER_INFO* mi, const char* master_info_fname,
   mi->inited = 1;
   // now change cache READ -> WRITE - must do this before flush_master_info
   reinit_io_cache(&mi->file, WRITE_CACHE,0L,0,1);
-  error=test(flush_master_info(mi));
+  if ((error=test(flush_master_info(mi))))
+    sql_print_error("Failed to flush master info file");
   pthread_mutex_unlock(&mi->data_lock);
   DBUG_RETURN(error);
 

sql/sql_repl.cc

@@ -159,10 +159,18 @@ File open_binlog(IO_CACHE *log, const char *log_file_name,
   File file;
   DBUG_ENTER("open_binlog");
 
-  if ((file = my_open(log_file_name, O_RDONLY | O_BINARY, MYF(MY_WME))) < 0 ||
-      init_io_cache(log, file, IO_SIZE*2, READ_CACHE, 0, 0,
+  if ((file = my_open(log_file_name, O_RDONLY | O_BINARY, MYF(MY_WME))) < 0)
+  {
+    sql_print_error("Failed to open log (\
+file '%s', errno %d)", log_file_name, my_errno);
+    *errmsg = "Could not open log file";	// This will not be sent
+    goto err;
+  }
+  if (init_io_cache(log, file, IO_SIZE*2, READ_CACHE, 0, 0,
 		    MYF(MY_WME | MY_DONT_CHECK_FILESIZE)))
   {
+    sql_print_error("Failed to create a cache on log (\
+file '%s')", log_file_name);
     *errmsg = "Could not open log file";	// This will not be sent
     goto err;
   }
@@ -743,6 +751,9 @@ int reset_slave(THD *thd, MASTER_INFO* mi)
   //Clear master's log coordinates (only for good display of SHOW SLAVE STATUS)
   mi->master_log_name[0]= 0;
   mi->master_log_pos= BIN_LOG_HEADER_SIZE;
+  //Clear the errors displayed by SHOW SLAVE STATUS
+  mi->rli.last_slave_error[0]=0;
+  mi->rli.last_slave_errno=0;
   //close master_info_file, relay_log_info_file, set mi->inited=rli->inited=0
   end_master_info(mi);
   //and delete these two files