Re: bzr commit into mysql-5.1-bugteam branch (Dao-Gang.Qu:2941) Bug#45214

[Daogang Qu]

Hi Zhenxing and Andrei,
Thanks for these good suggestions, which make things perfect. Please
review the newest patch. Thanks!

> Hi,
>
> There are some suggestions, you can have a look!
>
> Dao-Gang.Qu@stripped wrote: 
>   
>> #At file:///home/daogangq/mysql/bzrwork/bug45214/5.1-bt/ based on
> revid:davi.arnaut@stripped
>>
>>  2941 Dao-Gang.Qu@stripped	2009-07-02
>>       Bug #45214  get_master_version_and_clock does not report error when queries
> fail
>>             
>>       The "get_master_version_and_clock(...)" function in sql/slave.cc ignores 
>>       error and passes directly when queries fail, or queries succeed 
>>       but the result retrieved is empty.
>>       
>>       The "get_master_version_and_clock(...)" function should try to reconnect
> master
>>       if queries fail because of transient network problems, and fail otherwise.
>>       The I/O thread should print a warning if the some system variables do not 
>>       exist on master (very old master)
>>      @ mysql-test/extra/rpl_tests/rpl_get_master_version_and_clock.test
>>         Added test file for bug #45214
>>      @ mysql-test/suite/rpl/r/rpl_get_master_version_and_clock.result
>>         Added test result for bug #45214
>>      @ mysql-test/suite/rpl/t/rpl_get_master_version_and_clock.test
>>         Added test file for bug #45214
>>      @ sql/slave.cc
>>         The 'is_network_error()' function is added for checking if the error is
> caused by network.
>>         Added a new return value (2) to 'get_master_version_and_clock()' function
> result set 
>>         to indicate transient network errors when queries fail, and the caller
> should 
>>         try to reconnect in this case.
>>
>>     added:
>>       mysql-test/extra/rpl_tests/rpl_get_master_version_and_clock.test
>>       mysql-test/suite/rpl/r/rpl_get_master_version_and_clock.result
>>       mysql-test/suite/rpl/t/rpl_get_master_version_and_clock.test
>>     modified:
>>       sql/slave.cc
>> === added file
> 'mysql-test/extra/rpl_tests/rpl_get_master_version_and_clock.test'
>> --- a/mysql-test/extra/rpl_tests/rpl_get_master_version_and_clock.test	1970-01-01
> 00:00:00 +0000
>> +++ b/mysql-test/extra/rpl_tests/rpl_get_master_version_and_clock.test	2009-07-02
> 10:55:59 +0000
>> @@ -0,0 +1,63 @@
>> +#
>> +# BUG#45214
>> +# The common part of the "rpl_get_master_version_and_clock" test. 
>> +# Restart slave under network disconnection between slave and master
>> +# following the steps:
>> +#    1 - Got DBUG_SYNC_POINT lock
>> +#    2 - Set DBUG_SYNC_POINT before call mysql_real_query(...) function in
> get_master_version_and_clock(...) function and hang here
>> +#    3 - shutdown master server for simulating network disconnection
>> +#    4 - Release DBUG_SYNC_POINT lock
>> +#    5 - Check if the slave I/O thread tries to reconnect to master. 
>> +#
>> +# Note: Please make sure initialize the $debug_lock when call the test script.
>> +#
>> +connection slave;
>> +if (`SELECT '$debug_lock' = ''`)
>> +{
>> +    --die Cannot continue. Please set value for $debug_lock.
>> +}
>> +
>> +# Restart slave
>> +--disable_warnings
>> +stop slave;
>> +source include/wait_for_slave_to_stop.inc;
>> +start slave;
>> +source include/wait_for_slave_to_start.inc;
>> +connection master;
>> +# Write file to make mysql-test-run.pl expect the "crash", but don't start
>> +# it until it's told to
>> +--write_file $MYSQLTEST_VARDIR/tmp/mysqld.1.expect
>> +wait
>> +EOF
>> +
>> +# Send shutdown to the connected server and give
>> +# it 10 seconds to die before zapping it
>> +shutdown_server 10;
>> +
>> +connection slave;
>> +eval SELECT RELEASE_LOCK($debug_lock);
>> +
>> +# Write file to make mysql-test-run.pl start up the server again
>> +--append_file $MYSQLTEST_VARDIR/tmp/mysqld.1.expect
>> +restart
>> +EOF
>> +
>> +connection master;
>> +# Turn on reconnect
>> +--enable_reconnect
>> +
>> +# Call script that will poll the server waiting for it to be back online again
>> +--source include/wait_until_connected_again.inc
>> +
>> +# Turn off reconnect again
>> +--disable_reconnect
>> +
>> +connection slave;
>> +source include/wait_for_slave_to_start.inc;
>> +
>> +# Show slave last IO errno
>> +let $last_io_errno= query_get_value("show slave status", Last_IO_Errno, 1);
>> +echo Slave_IO_Errno= $last_io_errno;
>> +
>> +
>> +# End of tests
>>
>> === added file 'mysql-test/suite/rpl/r/rpl_get_master_version_and_clock.result'
>> --- a/mysql-test/suite/rpl/r/rpl_get_master_version_and_clock.result	1970-01-01
> 00:00:00 +0000
>> +++ b/mysql-test/suite/rpl/r/rpl_get_master_version_and_clock.result	2009-07-02
> 10:55:59 +0000
>> @@ -0,0 +1,40 @@
>> +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;
>> +SELECT IS_FREE_LOCK("debug_lock.before_get_UNIX_TIMESTAMP");
>> +IS_FREE_LOCK("debug_lock.before_get_UNIX_TIMESTAMP")
>> +1
>> +SELECT GET_LOCK("debug_lock.before_get_UNIX_TIMESTAMP", 1000);
>> +GET_LOCK("debug_lock.before_get_UNIX_TIMESTAMP", 1000)
>> +1
>> +set global debug= 'd,debug_lock.before_get_UNIX_TIMESTAMP';
>> +stop slave;
>> +start slave;
>> +SELECT RELEASE_LOCK("debug_lock.before_get_UNIX_TIMESTAMP");
>> +RELEASE_LOCK("debug_lock.before_get_UNIX_TIMESTAMP")
>> +1
>> +Slave_IO_Errno= 2013
>> +SELECT IS_FREE_LOCK("debug_lock.before_get_SERVER_ID");
>> +IS_FREE_LOCK("debug_lock.before_get_SERVER_ID")
>> +1
>> +SELECT GET_LOCK("debug_lock.before_get_SERVER_ID", 1000);
>> +GET_LOCK("debug_lock.before_get_SERVER_ID", 1000)
>> +1
>> +set global debug= 'd,debug_lock.before_get_SERVER_ID';
>> +stop slave;
>> +start slave;
>> +SELECT RELEASE_LOCK("debug_lock.before_get_SERVER_ID");
>> +RELEASE_LOCK("debug_lock.before_get_SERVER_ID")
>> +1
>> +Slave_IO_Errno= 2013
>> +set global debug= '';
>> +reset master;
>> +include/stop_slave.inc
>> +change master to master_port=SLAVE_PORT;
>> +start slave;
>> +*** must be having the replicate-same-server-id IO thread error ***
>> +Slave_IO_Errno= 1593
>> +Slave_IO_Error= Fatal error: The slave I/O thread stops because master and slave
> have equal MySQL server ids; these ids must be different for replication to work (or the
> --replicate-same-server-id option must be used on slave but this does not always make
> sense; please check the manual before using it).
>>
>> === added file 'mysql-test/suite/rpl/t/rpl_get_master_version_and_clock.test'
>> --- a/mysql-test/suite/rpl/t/rpl_get_master_version_and_clock.test	1970-01-01
> 00:00:00 +0000
>> +++ b/mysql-test/suite/rpl/t/rpl_get_master_version_and_clock.test	2009-07-02
> 10:55:59 +0000
>> @@ -0,0 +1,60 @@
>> +#
>> +# BUG#45214 
>> +# This test verifies if the slave I/O tread tries to reconnect to
>> +# master when it tries to get the values of the UNIX_TIMESTAMP, SERVER_ID,
>> +# COLLATION_SERVER and TIME_ZONE from master under network disconnection.
>> +# The COLLATION_SERVER and TIME_ZONE are got only on master server version 4.
>> +# So they can't be verified by test case here.
>> +# Finish the following tests by calling its common test script:  
>> +# extra/rpl_tests/rpl_get_master_version_and_clock.test. 
>> +# And meanwhile this test checks that the slave I/O thread refuses to start if
> slave
>> +# and master have the same server id (because this is a useless setup,
>> +# and otherwise SHOW SLAVE STATUS shows progress but all queries are
>> +# ignored, which has caught our customers), unless
>> +# --replicate-same-server-id.
>> +#
>> +
>> +source include/master-slave.inc;
>> +
>> +#Test case 1: Try to get the value of the UNIX_TIMESTAMP from master under
> network disconnection
>> +connection slave;
>> +let $debug_saved= `select @@global.debug`;
>> +
>> +let $debug_lock= "debug_lock.before_get_UNIX_TIMESTAMP";
>> +eval SELECT IS_FREE_LOCK($debug_lock);
>> +eval SELECT GET_LOCK($debug_lock, 1000);
>> +
>> +set global debug= 'd,debug_lock.before_get_UNIX_TIMESTAMP';
>> +source extra/rpl_tests/rpl_get_master_version_and_clock.test; 
>> +
>> +#Test case 2: Try to get the value of the SERVER_ID from master under network
> disconnection
>> +connection slave;
>> +let $debug_lock= "debug_lock.before_get_SERVER_ID";
>> +eval SELECT IS_FREE_LOCK($debug_lock);
>> +eval SELECT GET_LOCK($debug_lock, 1000);
>> +
>> +set global debug= 'd,debug_lock.before_get_SERVER_ID';
>> +source extra/rpl_tests/rpl_get_master_version_and_clock.test;
>> +
>> +eval set global debug= '$debug_saved';
>> +
>> +#Test case 3: This test checks that the slave I/O thread refuses to start
>> +#if slave and master have the same server id.
>> +connection slave;
>> +reset master;
>> +# replicate ourselves
>> +source include/stop_slave.inc;
>> +--replace_result $SLAVE_MYPORT SLAVE_PORT
>> +eval change master to master_port=$SLAVE_MYPORT;
>> +start slave;
>> +
>> +let $slave_param= Last_IO_Errno;
>> +let $slave_param_value= 1593;
>> +source include/wait_for_slave_param.inc;
>> +--echo *** must be having the replicate-same-server-id IO thread error ***
>> +let $last_io_errno= query_get_value("show slave status", Last_IO_Errno, 1);
>> +let $last_io_error= query_get_value("show slave status", Last_IO_Error, 1);
>> +echo Slave_IO_Errno= $last_io_errno;
>> +echo Slave_IO_Error= $last_io_error;
>> +
>> +# End of tests
>>
>> === modified file 'sql/slave.cc'
>> --- a/sql/slave.cc	2009-06-09 16:44:26 +0000
>> +++ b/sql/slave.cc	2009-07-02 10:55:59 +0000
>> @@ -38,6 +38,7 @@
>>  #include <my_dir.h>
>>  #include <sql_common.h>
>>  #include <errmsg.h>
>> +#include <mysqld_error.h>
>>  #include <mysys_err.h>
>>  
>>  #ifdef HAVE_REPLICATION
>> @@ -842,6 +843,29 @@ int init_intvar_from_file(int* var, IO_C
>>    DBUG_RETURN(1);
>>  }
>>  
>> +
>> +/*
>> +  Check if the error is caused by network.
>> +  @param[in]   errorno   Number of the error.
>> +  RETURNS:
>> +  TRUE         network error
>> +  FALSE        not network error
>> +*/
>> +
>> +bool is_network_error(uint errorno)
>> +{ 
>> +  if (errorno == CR_CONNECTION_ERROR || 
>> +      errorno == CR_CONN_HOST_ERROR ||
>> +      errorno == CR_SERVER_GONE_ERROR ||
>> +      errorno == CR_SERVER_LOST ||
>> +      errorno == ER_CON_COUNT_ERROR ||
>> +      errorno == ER_SERVER_SHUTDOWN)
>> +    return TRUE;
>> +
>> +  return FALSE;   
>> +}
>> +
>> +
>>  /*
>>    Note that we rely on the master's version (3.23, 4.0.14 etc) instead of
>>    relying on the binlog's version. This is not perfect: imagine an upgrade
>> @@ -854,6 +878,7 @@ int init_intvar_from_file(int* var, IO_C
>>    RETURNS
>>    0       ok
>>    1       error
>> +  2       transient network problem, the caller should try to reconnect
>>  */
>>  
>>  static int get_master_version_and_clock(MYSQL* mysql, Master_info* mi)
>> @@ -864,6 +889,7 @@ static int get_master_version_and_clock(
>>    MYSQL_RES *master_res= 0;
>>    MYSQL_ROW master_row;
>>    DBUG_ENTER("get_master_version_and_clock");
>> +  int query_re= 0;
>>  
>>    /*
>>      Free old description_event_for_queue (that is needed if we are in
>> @@ -938,21 +964,37 @@ static int get_master_version_and_clock(
>>      Compare the master and slave's clock. Do not die if master's clock is
>>      unavailable (very old master not supporting UNIX_TIMESTAMP()?).
>>    */
>> +  DBUG_SYNC_POINT("debug_lock.before_get_UNIX_TIMESTAMP", 10);
>> +  query_re= mysql_real_query(mysql, STRING_WITH_LEN("SELECT
> UNIX_TIMESTAMP()"));
>> +  if ((query_re || !(master_res= mysql_store_result(mysql))) && 
>> +       is_network_error(mysql_errno(mysql)))
>> +  {
>>     
>
> master_res= NULL;
> if ((!mysql_real_query(...) &&
>      (master_res= mysql_store_result(...)) &&
>      (master_row= mysql_fetch_row(...)))
> {
>    // Query is OK
> }
> else if (is_network_error(...))
> {
>   // Network error
> }
> else
> {
>   // Fatal error
> }
>
> This can reduce merge problem and can make it more clear to understand.
>
>   
There are some minor difference in other three cases. I think you are
agree with them.
>> +    mi->report(WARNING_LEVEL, mysql_errno(mysql),
>> +               "Get master clock failed with error: %s", mysql_error(mysql));
>> +    DBUG_RETURN(2);
>> +  }
>>  
>> -  if (!mysql_real_query(mysql, STRING_WITH_LEN("SELECT UNIX_TIMESTAMP()"))
> &&
>> -      (master_res= mysql_store_result(mysql)) &&
>> -      (master_row= mysql_fetch_row(master_res)))
>> +  if ((master_row= mysql_fetch_row(master_res)))
>>    {
>>      mi->clock_diff_with_master=
>>        (long) (time((time_t*) 0) - strtoul(master_row[0], 0, 10));
>>    }
>> +  else if (is_network_error(mysql_errno(mysql)))
>> +  { 
>> +    mi->report(WARNING_LEVEL, mysql_errno(mysql),
>> +               "Get master clock failed with error: %s", mysql_error(mysql));
>> +    if (master_res)
>> +      mysql_free_result(master_res);
>> +    DBUG_RETURN(2);
>> +  }
>>    else if (!check_io_slave_killed(mi->io_thd, mi, NULL))
>>     
>
> move this out of the function, check_io_slave_killed() in the caller.
>
>   
Done it.
>> {
>>      mi->clock_diff_with_master= 0; /* The "most sensible" value */
>> -    sql_print_warning("\"SELECT UNIX_TIMESTAMP()\" failed on master, "
>> -                      "do not trust column Seconds_Behind_Master of SHOW "
>> -                      "SLAVE STATUS. Error: %s (%d)",
>> -                      mysql_error(mysql), mysql_errno(mysql));
>> +    mi->report(ERROR_LEVEL, ER_UNKNOWN_ERROR,
>> +               "\"SELECT UNIX_TIMESTAMP()\" failed on master, "
>> +               "do not trust column Seconds_Behind_Master of SHOW "
>> +               "SLAVE STATUS. Error: %s (%d)",
>> +               mysql_error(mysql), mysql_errno(mysql));
>>     
>
> This should be a warning.
>
>   
Yes. Right.
>> }
>>    if (master_res)
>>      mysql_free_result(master_res);
>> @@ -967,26 +1009,54 @@ static int get_master_version_and_clock(
>>      Note: we could have put a @@SERVER_ID in the previous SELECT
>>      UNIX_TIMESTAMP() instead, but this would not have worked on 3.23 masters.
>>    */
>> -  if (!mysql_real_query(mysql,
>> -                        STRING_WITH_LEN("SHOW VARIABLES LIKE 'SERVER_ID'"))
> &&
>> -      (master_res= mysql_store_result(mysql)))
>> -  {
>> -    if ((master_row= mysql_fetch_row(master_res)) &&
>> -        (::server_id == strtoul(master_row[1], 0, 10)) &&
>> -        !mi->rli.replicate_same_server_id)
>> +  DBUG_SYNC_POINT("debug_lock.before_get_SERVER_ID", 10);
>> +  query_re= mysql_real_query(mysql, STRING_WITH_LEN("SHOW VARIABLES LIKE
> 'SERVER_ID'"));
>> +  if (query_re || !(master_res= mysql_store_result(mysql)))
>> +  { 
>> +    if (is_network_error(mysql_errno(mysql)))
>>      {
>> -      errmsg= "The slave I/O thread stops because master and slave have equal \
>> +      mi->report(WARNING_LEVEL, mysql_errno(mysql),
>> +                 "Get master SERVER_ID failed with error: %s",
> mysql_error(mysql));
>> +      DBUG_RETURN(2);
>> +    }
>> +    /* Fatal error */
>> +    errmsg= "The slave I/O thread stops because a fatal error is encountered \
>> +when it try to get the value of SERVER_ID variable from master.";
>> +    err_code= ER_SLAVE_FATAL_ERROR;
>> +    sprintf(err_buff, ER(err_code), errmsg);
>> +    goto err;
>> +  }
>> +
>> +  master_row= mysql_fetch_row(master_res);
>> +  if (master_row && (::server_id == strtoul(master_row[1], 0, 10))
> &&
>> +      !mi->rli.replicate_same_server_id)
>> +  {
>> +    errmsg= "The slave I/O thread stops because master and slave have equal \
>>  MySQL server ids; these ids must be different for replication to work (or \
>>  the --replicate-same-server-id option must be used on slave but this does \
>>  not always make sense; please check the manual before using it).";
>> -      err_code= ER_SLAVE_FATAL_ERROR;
>> -      sprintf(err_buff, ER(err_code), errmsg);
>> +    err_code= ER_SLAVE_FATAL_ERROR;
>> +    sprintf(err_buff, ER(err_code), errmsg);
>> +  }
>> +  else if (!master_row)
>> +  {
>> +    if (is_network_error(mysql_errno(mysql)))
>> +    {
>> +      mi->report(WARNING_LEVEL, mysql_errno(mysql),
>> +                 "Get master SERVER_ID failed with error: %s",
> mysql_error(mysql));
>> +      mysql_free_result(master_res);
>> +      DBUG_RETURN(2);
>>      }
>> -    mysql_free_result(master_res);
>> -    if (errmsg)
>> -      goto err;
>> +    else
>> +      mi->report(WARNING_LEVEL, ER_UNKNOWN_SYSTEM_VARIABLE, 
>> +                 "Unknown system variable 'SERVER_ID' on master, \
>> +maybe it is a very old master.");
>>    }
>> +  mysql_free_result(master_res);
>>  
>> +  if (errmsg)
>> +    goto err;
>>     
>
> put the goto where errmsg was set.
>
>   
Done it.
>> + 
>>    /*
>>      Check that the master's global character_set_server and ours are the same.
>>      Not fatal if query fails (old master?).
>> @@ -1008,23 +1078,55 @@ not always make sense; please check the 
>>    if (*mysql->server_version == '3')
>>      goto err;
>>  
>> -  if ((*mysql->server_version == '4') &&
>> -      !mysql_real_query(mysql,
>> -                        STRING_WITH_LEN("SELECT @@GLOBAL.COLLATION_SERVER"))
> &&
>> -      (master_res= mysql_store_result(mysql)))
>> +  if (*mysql->server_version == '4')
>>    {
>> -    if ((master_row= mysql_fetch_row(master_res)) &&
>> -        strcmp(master_row[0],
> global_system_variables.collation_server->name))
>> +    query_re= mysql_real_query(mysql, STRING_WITH_LEN("SELECT
> @@GLOBAL.COLLATION_SERVER"));
>> +    if (query_re || !(master_res= mysql_store_result(mysql)))
>>      {
>> -      errmsg= "The slave I/O thread stops because master and slave have \
>> +      if (is_network_error(mysql_errno(mysql)))
>> +      {
>> +        mi->report(WARNING_LEVEL, mysql_errno(mysql),
>> +                   "Get master COLLATION_SERVER failed with error: %s",
> mysql_error(mysql)); 
>> +        DBUG_RETURN(2);
>> +      }
>> +
>> +      if (mysql_errno(mysql) != ER_UNKNOWN_SYSTEM_VARIABLE)
>> +      {
>> +        /* Fatal error */
>> +        errmsg= "The slave I/O thread stops because a fatal error is encountered
> \
>> +when it try to get the value of COLLATION_SERVER global variable from master.";
>> +        err_code= ER_SLAVE_FATAL_ERROR;
>> +        sprintf(err_buff, ER(err_code), errmsg);
>> +        goto err;
>> +      }
>> +      else
>> +        mi->report(WARNING_LEVEL, ER_UNKNOWN_SYSTEM_VARIABLE,
>> +                   "Unknown system variable 'COLLATION_SERVER' on master, \
>> +maybe it is a very old master.");
>> +    }
>> +    else
>> +    {
>> +      master_row= mysql_fetch_row(master_res);
>> +      if (master_row && strcmp(master_row[0],
>> +                              
> global_system_variables.collation_server->name))
>> +      {  
>> +        errmsg= "The slave I/O thread stops because master and slave have \
>>  different values for the COLLATION_SERVER global variable. The values must \
>>  be equal for replication to work";
>> -      err_code= ER_SLAVE_FATAL_ERROR;
>> -      sprintf(err_buff, ER(err_code), errmsg);
>> +        err_code= ER_SLAVE_FATAL_ERROR;
>> +        sprintf(err_buff, ER(err_code), errmsg);
>> +      }
>> +      else if (!master_row && is_network_error(mysql_errno(mysql)))
>> +      {
>> +        mi->report(WARNING_LEVEL, mysql_errno(mysql),
>> +                   "Get master COLLATION_SERVER failed with error: %s",
> mysql_error(mysql));
>> +        mysql_free_result(master_res);
>> +        DBUG_RETURN(2);
>> +      }
>> +      mysql_free_result(master_res);
>> +      if (errmsg)
>> +        goto err;
>>      }
>> -    mysql_free_result(master_res);
>> -    if (errmsg)
>> -      goto err;
>>    }
>>  
>>    /*
>> @@ -1042,13 +1144,28 @@ be equal for replication to work";
>>      This check is only necessary for 4.x masters (and < 5.0.4 masters but
>>      those were alpha).
>>    */
>> -  if ((*mysql->server_version == '4') &&
>> -      !mysql_real_query(mysql, STRING_WITH_LEN("SELECT @@GLOBAL.TIME_ZONE"))
> &&
>> -      (master_res= mysql_store_result(mysql)))
>> -  {
>> -    if ((master_row= mysql_fetch_row(master_res)) &&
>> -        strcmp(master_row[0],
>> -               global_system_variables.time_zone->get_name()->ptr()))
>> +  if (*mysql->server_version == '4')
>> +  {
>> +    query_re= mysql_real_query(mysql, STRING_WITH_LEN("SELECT
> @@GLOBAL.TIME_ZONE"));
>> +    if (query_re || !(master_res= mysql_store_result(mysql)))
>> +    {
>> +      if (is_network_error(mysql_errno(mysql)))
>> +      {
>> +        mi->report(WARNING_LEVEL, mysql_errno(mysql),
>> +                   "Get master TIME_ZONE failed with error: %s",
> mysql_error(mysql));
>> +        DBUG_RETURN(2);
>> +      }
>> +      /* Fatal error */
>> +      errmsg= "The slave I/O thread stops because a fatal error is encountered
> \
>> +when it try to get the value of TIME_ZONE global variable from master.";
>> +      err_code= ER_SLAVE_FATAL_ERROR;
>> +      sprintf(err_buff, ER(err_code), errmsg);
>> +      goto err;
>> +    }
>> +
>> +    master_row= mysql_fetch_row(master_res);
>> +    if (master_row && strcmp(master_row[0],
>> +                            
> global_system_variables.time_zone->get_name()->ptr()))
>>      {
>>        errmsg= "The slave I/O thread stops because master and slave have \
>>  different values for the TIME_ZONE global variable. The values must \
>> @@ -1056,6 +1173,13 @@ be equal for replication to work";
>>        err_code= ER_SLAVE_FATAL_ERROR;
>>        sprintf(err_buff, ER(err_code), errmsg);
>>      }
>> +    else if (!master_row && is_network_error(mysql_errno(mysql)))
>> +    {
>> +      mi->report(WARNING_LEVEL, mysql_errno(mysql),
>> +                 "Get master TIME_ZONE failed with error: %s",
> mysql_error(mysql));
>> +      mysql_free_result(master_res);
>> +      DBUG_RETURN(2);
>> +    }    
>>      mysql_free_result(master_res);
>>  
>>      if (errmsg)
>> @@ -2372,6 +2496,7 @@ pthread_handler_t handle_slave_io(void *
>>    char llbuff[22];
>>    uint retry_count;
>>    bool suppress_warnings;
>> +  int ret;
>>  #ifndef DBUG_OFF
>>    uint retry_count_reg= 0, retry_count_dump= 0, retry_count_event= 0;
>>  #endif
>> @@ -2451,8 +2576,20 @@ connected:
>>    mi->slave_running= MYSQL_SLAVE_RUN_CONNECT;
>>    thd->slave_net = &mysql->net;
>>    thd_proc_info(thd, "Checking master version");
>> -  if (get_master_version_and_clock(mysql, mi))
>> +  ret= get_master_version_and_clock(mysql, mi);
>> +  if (ret == 1)
>> +    /* Fatal error */
>>      goto err;
>> +  
>> +  if (ret == 2) 
>> +  {
>> +    suppress_warnings= FALSE;
>>     
>
> check_io_slave_killed() here.
>
>   
added.
>> +    /* Try to reconnect because the error was caused by a transient network
> problem */
>> +    if (try_to_reconnect(thd, mysql, mi, &retry_count, suppress_warnings,
>> +                             reconnect_messages[SLAVE_RECON_ACT_REG]))
>> +      goto err;
>> +    goto connected;
>> +  } 
>>  
>>    if (mi->rli.relay_log.description_event_for_queue->binlog_version >
> 1)
>>    {
>>     
>
>
>   
Best Regards,

Daogang