MySQL: Pacemaker cannot start the failed master as a new slave

corosyncfailoverhigh-availabilitymysql-replicationpacemaker

pacemaker-1.0.12-1
corosync-1.2.7-1.1

I'm going to setup failover for MySQL replication (1 master and 1 slave)
follow this guide:
https://github.com/jayjanssen/Percona-Pacemaker-Resource-Agents/blob/master/doc/PRM-setup-guide.rst

Here're the output of crm configure show:

node serving-6192 \
    attributes p_mysql_mysql_master_IP="192.168.6.192"
node svr184R-638.localdomain \
    attributes p_mysql_mysql_master_IP="192.168.6.38"
primitive p_mysql ocf:percona:mysql \
    params config="/etc/my.cnf" pid="/var/run/mysqld/mysqld.pid"
socket="/var/lib/mysql/mysql.sock" replication_user="repl"
replication_passwd="x" test_user="test_user" test_passwd="x" \
    op monitor interval="5s" role="Master" OCF_CHECK_LEVEL="1" \
    op monitor interval="2s" role="Slave" timeout="30s"
OCF_CHECK_LEVEL="1" \
    op start interval="0" timeout="120s" \
    op stop interval="0" timeout="120s"
primitive writer_vip ocf:heartbeat:IPaddr2 \
    params ip="192.168.6.8" cidr_netmask="32" \
    op monitor interval="10s" \
    meta is-managed="true"
ms ms_MySQL p_mysql \
    meta master-max="1" master-node-max="1" clone-max="2"
clone-node-max="1" notify="true" globally-unique="false"
target-role="Master" is-managed="true"
colocation writer_vip_on_master inf: writer_vip ms_MySQL:Master
order ms_MySQL_promote_before_vip inf: ms_MySQL:promote writer_vip:start
property $id="cib-bootstrap-options" \
    dc-version="1.0.12-unknown" \
    cluster-infrastructure="openais" \
    expected-quorum-votes="2" \
    no-quorum-policy="ignore" \
    stonith-enabled="false" \
    last-lrm-refresh="1341801689"
property $id="mysql_replication" \
    p_mysql_REPL_INFO="192.168.6.192|mysql-bin.000006|338"

crm_mon:

Last updated: Mon Jul  9 10:30:01 2012
Stack: openais
Current DC: serving-6192 - partition with quorum
Version: 1.0.12-unknown
2 Nodes configured, 2 expected votes
2 Resources configured.
============

Online: [ serving-6192 svr184R-638.localdomain ]

 Master/Slave Set: ms_MySQL
     Masters: [ serving-6192 ]
     Slaves: [ svr184R-638.localdomain ]
writer_vip    (ocf::heartbeat:IPaddr2):    Started serving-6192

Editing /etc/my.cnf on the serving-6192 of wrong syntax to test
failover and it's working fine:

svr184R-638.localdomain being promoted to become the master
writer_vip switch to svr184R-638.localdomain

Current state:

Last updated: Mon Jul  9 10:35:57 2012
Stack: openais
Current DC: serving-6192 - partition with quorum
Version: 1.0.12-unknown
2 Nodes configured, 2 expected votes
2 Resources configured.
============

Online: [ serving-6192 svr184R-638.localdomain ]

 Master/Slave Set: ms_MySQL
     Masters: [ svr184R-638.localdomain ]
     Stopped: [ p_mysql:0 ]
writer_vip    (ocf::heartbeat:IPaddr2):    Started svr184R-638.localdomain

Failed actions:
    p_mysql:0_monitor_5000 (node=serving-6192, call=15, rc=7,
status=complete): not running
    p_mysql:0_demote_0 (node=serving-6192, call=22, rc=7,
status=complete): not running
    p_mysql:0_start_0 (node=serving-6192, call=26, rc=-2, status=Timed
Out): unknown exec error

Remove the wrong syntax from /etc/my.cnf on serving-6192, and restart
corosync, what I would like to see is serving-6192 being started as a new
slave but it doesn't:

Failed actions:
    p_mysql:0_start_0 (node=serving-6192, call=4, rc=1,
status=complete): unknown error

Here're snippet of the logs which I'm suspecting:

Jul 09 10:46:32 serving-6192 lrmd: [7321]: info: rsc:p_mysql:0:4: start
Jul 09 10:46:32 serving-6192 lrmd: [7321]: info: RA output:
(p_mysql:0:start:stderr) Error performing operation: The
object/attribute does not exist

Jul 09 10:46:32 serving-6192 crm_attribute: [7420]: info: Invoked:
/usr/sbin/crm_attribute -N serving-6192 -l reboot --name readable -v 0

/var/log/cluster/corosync.log: http://fpaste.org/AyOZ/

The strange thing is I can starting it manually:

export OCF_ROOT=/usr/lib/ocf
export OCF_RESKEY_config="/etc/my.cnf"
export OCF_RESKEY_pid="/var/run/mysqld/mysqld.pid"
export OCF_RESKEY_socket="/var/lib/mysql/mysql.sock"
export OCF_RESKEY_replication_user="repl"
export OCF_RESKEY_replication_passwd="x"
export OCF_RESKEY_test_user="test_user"
export OCF_RESKEY_test_passwd="x"

sh -x /usr/lib/ocf/resource.d/percona/mysql start: http://fpaste.org/RVGh/

Did I make something wrong?

Reply to @Patrick Fri Jul 13 10:22:10 ICT 2012:

I'm not sure why its failing as your log doesnt contain any messages
from the resource script (the ocf_log commands)

I take it all from /var/log/cluster/corosync.log. Have you got any reason in your mind?

/etc/corosync/corosync.conf

compatibility: whitetank

totem {
    version: 2
    secauth: off
    threads: 0
    interface {
        member {
            memberaddr: 192.168.6.192
        }
        member {
            memberaddr: 192.168.6.38
        }
        ringnumber: 0
        bindnetaddr: 192.168.6.0
        mcastaddr: 226.94.1.1
        mcastport: 5405
    }
}

logging {
    fileline: off
    to_stderr: yes
    to_logfile: yes
    to_syslog: yes
    logfile: /var/log/cluster/corosync.log
    debug: on
    timestamp: on
    logger_subsys {
        subsys: AMF
        debug: off
    }
}

amf {
    mode: disabled
}

Also the reason the script works when you run it manually is because
you're not setting the variables which tells the script its a
master/slave resource. So when it runs, the script thinks its just a
single standalone instance.

Thanks. I've appended the following variables to my ~/.bash_profile:

export OCF_RESKEY_CRM_meta_clone_max="2"
export OCF_RESKEY_CRM_meta_role="Slave"

Make it take effect . ~/.bash_profile and manually start mysql resource:

sh -x /usr/lib/ocf/resource.d/percona/mysql start: http://fpaste.org/EMwa/

and it works fine:

mysql> show slave status\G
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 192.168.6.38
                  Master_User: repl
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: mysql-bin.000072
          Read_Master_Log_Pos: 1428602
               Relay_Log_File: mysqld-relay-bin.000006
                Relay_Log_Pos: 39370
        Relay_Master_Log_File: mysql-bin.000072
             Slave_IO_Running: Yes
            Slave_SQL_Running: Yes
              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: 1428602
              Relay_Log_Space: 39527
              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: 0
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: 123
1 row in set (0.00 sec)

Stop MySQL, turn on the debug, restart corosync, and here're the logs: http://fpaste.org/mZzS/

As you can see, nothing but 'unknown error':

 1.
    Jul 13 10:48:06 serving-6192 crmd: [3341]: debug:
    get_xpath_object: No match for
    //cib_update_result//diff-added//crm_config in
    /notify/cib_update_result/diff
 2.
    Jul 13 10:48:06 serving-6192 lrmd: [3338]: WARN: Managed
    p_mysql:1:start process 3416 exited with return code 1.
 3.
    Jul 13 10:48:06 serving-6192 crmd: [3341]: info:
    process_lrm_event: LRM operation p_mysql:1_start_0 (call=4,
    rc=1, cib-update=10, confirmed=true) unknown error

Any thoughts?

UPDATE Sat Jul 14 17:16:03 ICT 2012:

@Patrick: thank you for your tips!

The environment variables that Pacemaker uses as follow: http://fpaste.org/92yN/

As I suspected when chatting with you, the node serving-6192 was started with the OCF_RESKEY_CRM_meta_master_max=1, therefore, due to the following code:

/usr/lib/ocf/resource.d/percona/mysql:

if ocf_is_ms; then
    mysql_extra_params="--skip-slave-start"
fi

/usr/lib/ocf//lib/heartbeat/ocf-shellfuncs:

ocf_is_ms() {
    [ ! -z "${OCF_RESKEY_CRM_meta_master_max}" ] && [ "${OCF_RESKEY_CRM_meta_master_max}" -gt 0 ]
}

the extra param --skip-slave-start is included:

ps -ef | grep mysql

root 18215 1 0 17:12 pts/4 00:00:00 /bin/sh /usr/bin/mysqld_safe --defaults-file=/etc/my.cnf --pid-file=/var/run/mysqld/mysqld.pid --socket=/var/lib/mysql/mysql.sock --datadir=/var/lib/mysql --user=mysql --skip-slave-start

mysql 19025 18215 1 17:12 pts/4 00:00:14 /usr/libexec/mysqld --defaults-file=/etc/my.cnf --basedir=/usr --datadir=/var/lib/mysql --plugin-dir=/usr/lib64/mysql/plugin --user=mysql --skip-slave-start --log-error=/var/log/mysqld.log --open-files-limit=8192 --pid-file=/var/run/mysqld/mysqld.pid --socket=/var/lib/mysql/mysql.sock --port=3306

but SQL thread is still running:

         Slave_IO_Running: Yes
        Slave_SQL_Running: Yes

and replication is working fine.

IFS=$'\n' ENV=( $(cat /tmp/16374.env) ); env -i - "${ENV[@]}" sh -x /usr/lib/ocf/resource.d/percona/mysql start: http://fpaste.org/x7xE/

I am hitting my head against the wall (: -> |

Best Answer

Eureka!

Both of us forgot a very very important log file, it's... /var/log/mysqld.log:

socket: '/var/lib/mysql/mysql.sock'  port: 3306  MySQL Community Server (GPL) by Atomicorp
[Note] Slave SQL thread initialized, starting replication in log 'mysql-bin.000082' at position 58569, relay log './mysqld-relay-bin.000002' position: 58715
[Note] Slave I/O thread: connected to master 'repl@192.168.6.38:3306',replication started in log 'mysql-bin.000082' at position 58569
[Warning] Aborted connection 10 to db: 'unconnected' user: 'test_user' host: 'localhost' (init_connect command failed)
[Warning] The MySQL server is running with the --read-only option so it cannot execute this statement
[Note] /usr/libexec/mysqld: Normal shutdown

As you can guess, I tracked the user activity by combining the binlog and init-connect:

init_connect = "INSERT INTO audit.accesslog (connect_time, user_host, connection_id) VALUES (NOW(), CURRENT_USER(), CONNECTION_ID());"

but serving-6192 is set read-only when starting as a slave, and then when Pacemaker perform monitor operation with test_user:

    # Check for test table
    ocf_run -q $MYSQL $MYSQL_OPTIONS_TEST \
        -e "SELECT COUNT(*) FROM $OCF_RESKEY_test_table"

init_connect command failed with the above error:

The MySQL server is running with the --read-only option so it cannot execute this statement

The solution is I should set the init_connect option to the empty string before initializing the monitor action (don't forget to turn it back when promoting a node to become a master)

To anyone who are using event scheduler: also note that you must turn it on when promoting a slave to become a master:

set_event_scheduler() {
    local es_val
    if ocf_is_true $1; then
        es_val="on"
    else
        es_val="off"
    fi
    ocf_run $MYSQL $MYSQL_OPTIONS_REPL \
        -e "SET GLOBAL event_scheduler=${es_val}"
}

get_event_scheduler() {
    # Check if event-scheduler is set
    local event_scheduler_state

    event_scheduler_state=`$MYSQL $MYSQL_OPTIONS_REPL \
        -e "SHOW VARIABLES" | grep event_scheduler | awk '{print $2}'`

    if [ "$event_scheduler_state" = "ON" ]; then
        return 0
    else
        return 1
    fi
}

mysql_promote() {
    local master_info

    if ( ! mysql_status err ); then
        return $OCF_NOT_RUNNING
    fi
    ocf_run $MYSQL $MYSQL_OPTIONS_REPL \
        -e "STOP SLAVE"

    # Set Master Info in CIB, cluster level attribute
    update_data_master_status
    master_info="$(get_local_ip)|$(get_master_status File)|$(get_master_status Position)"
    ${CRM_ATTR_REPL_INFO} -v "$master_info"
    rm -f $tmpfile

    set_read_only off || return $OCF_ERR_GENERIC
    set_event_scheduler on || return $OCF_ERR_GENERIC

Also don't forget to turn it off when demoting:

    'pre-demote')
        # Is the notification for our set
        notify_resource=`echo $OCF_RESKEY_CRM_meta_notify_demote_resource|cut -d: -f1`
        my_resource=`echo $OCF_RESOURCE_INSTANCE|cut -d: -f1`
        if [ $notify_resource != ${my_resource} ]; then
            ocf_log debug "Notification is not for us"
            return $OCF_SUCCESS
        fi

        demote_host=`echo $OCF_RESKEY_CRM_meta_notify_demote_uname|tr -d " "`
        if [ $demote_host = ${HOSTNAME} ]; then
            ocf_log info "post-demote notification for $demote_host"
            set_read_only on
            set_event_scheduler off

Cheers,

Best Answer

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