Monthly Archives: July 2015

Which processes are swapping?!

Publicat la 27 July 2015 1 comentariu

Recently one machine was swapping. No free space on the swap partition. Hmmm... Since this machine was used as a database server, obviously I suspected mysql. But why to guess when I could knew for sure which process was swapping...

[codesyntax lang="bash"]

for file in /proc/*/status ; do awk '/VmSwap|Name/{printf $2 " " $3}END{ print ""}' $file; done | sort -k 2 -n -r | less

[/codesyntax]

Wasn't mysql but collectd btw :)

Topology refactoring using classic MySQL replication commands - version 2

Publicat la 17 July 2015 No comments

This one in not very different than Topology refactoring using classic MySQL replication commands - version 1, actually it's the other way around.

Context:

  • Initial state: 
    dbfoo1(M) - dbfoo2(S)
          \ dbfoo3(S)
  • Desired state: 
    dbfoo1(M) - dbfoo2(MS) - dbrfoo3(S)

    • Let's get it done:

    1. stop slave on dbfoo3
      2. MariaDB [(none)]> stop slave;
    2. check the "freezing point" on dbfoo2 and note down the output from 'show' commands
      3. MariaDB [(none)]> stop slave; show master status\Gshow slave status\Gstart slave;

*************************** 1. row ***************************
            File: bin.009642
        Position: 91547140
    Binlog_Do_DB: 
Binlog_Ignore_DB: 
1 row in set (0.00 sec)

*************************** 1. row ***************************
               Slave_IO_State: 
                  Master_Host: dbfoo1
                  Master_User: user
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: bin.293567
          Read_Master_Log_Pos: 90061272
               Relay_Log_File: relay.028914
                Relay_Log_Pos: 90061553
        Relay_Master_Log_File: bin.293567
             Slave_IO_Running: No
            Slave_SQL_Running: No
              Replicate_Do_DB: 
          Replicate_Ignore_DB: 
           Replicate_Do_Table: 
       Replicate_Ignore_Table: 
      Replicate_Wild_Do_Table: 
  Replicate_Wild_Ignore_Table: 
                   Last_Errno: 0
                   Last_Error: 
                 Skip_Counter: 0
          Exec_Master_Log_Pos: 90061272
              Relay_Log_Space: 90062173
              Until_Condition: None
               Until_Log_File: 
                Until_Log_Pos: 0
           Master_SSL_Allowed: No
           Master_SSL_CA_File: 
           Master_SSL_CA_Path: 
              Master_SSL_Cert: 
            Master_SSL_Cipher: 
               Master_SSL_Key: 
        Seconds_Behind_Master: NULL
Master_SSL_Verify_Server_Cert: No
                Last_IO_Errno: 0
                Last_IO_Error: 
               Last_SQL_Errno: 0
               Last_SQL_Error: 
  Replicate_Ignore_Server_Ids: 
             Master_Server_Id: 270
               Master_SSL_Crl: 
           Master_SSL_Crlpath: 
                   Using_Gtid: No
                  Gtid_IO_Pos: 
1 row in set (0.00 sec)

Query OK, 0 rows affected (0.00 sec)
    3. make sure dbfoo3 has the same data as dbfoo2 and use Relay_Master_Log_File and Exec_Master_Log_Pos from show master status
      4. MariaDB [(none)]> start slave until master_log_file='bin.293567', master_log_pos=90061272;
    4. point dbfoo3 to dbfoo2 and start the slave
      5. MariaDB [(none)]> stop slave;
MariaDB [(none)]> change master to master_host='foo2', master_log_file='bin.009642', master_log_pos=91547140;
MariaDB [(none)]> start slave;