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MYsql got Hang on High Load

Discussion in 'Database Discussions' started by fancier, Oct 23, 2012.

  1. fancier

    fancier Member

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    When there is high load

    more users at a time on my SMF (forum) then MYsql got Hang.

    Please see

    my.cnf

    my.cnf is here


    # Example MySQL config file for very large systems.
    #
    # This is for a large system with memory of 1G-2G where the system runs mainly
    # MySQL.
    #
    # MySQL programs look for option files in a set of
    # locations which depend on the deployment platform.
    # You can copy this option file to one of those
    # locations. For information about these locations, see:
    # MySQL :: MySQL 5.5 Reference Manual :: 4.2.3.3 Using Option Files
    #
    # In this file, you can use all long options that a program supports.
    # If you want to know which options a program supports, run the program
    # with the "--help" option.

    # The following options will be passed to all MySQL clients
    [client]
    #password = your_password
    port = 3306
    socket = /var/lib/mysql/mysql.sock

    # Here follows entries for some specific programs

    # The MySQL server
    [mysqld]
    port = 3306
    socket = /var/lib/mysql/mysql.sock
    skip-locking
    key_buffer_size = 384M
    max_allowed_packet = 1M
    table_open_cache = 512
    sort_buffer_size = 2M
    read_buffer_size = 2M
    read_rnd_buffer_size = 8M
    myisam_sort_buffer_size = 64M
    thread_cache_size = 8
    query_cache_size = 32M
    # Try number of CPU's*2 for thread_concurrency
    thread_concurrency = 8

    # Don't listen on a TCP/IP port at all. This can be a security enhancement,
    # if all processes that need to connect to mysqld run on the same host.
    # All interaction with mysqld must be made via Unix sockets or named pipes.
    # Note that using this option without enabling named pipes on Windows
    # (via the "enable-named-pipe" option) will render mysqld useless!
    #
    #skip-networking

    # Replication Master Server (default)
    # binary logging is required for replication
    log-bin=mysql-bin

    # required unique id between 1 and 2^32 - 1
    # defaults to 1 if master-host is not set
    # but will not function as a master if omitted
    server-id = 1

    # Replication Slave (comment out master section to use this)
    #
    # To configure this host as a replication slave, you can choose between
    # two methods :
    #
    # 1) Use the CHANGE MASTER TO command (fully described in our manual) -
    # the syntax is:
    #
    # CHANGE MASTER TO MASTER_HOST=<host>, MASTER_PORT=<port>,
    # MASTER_USER=<user>, MASTER_PASSWORD=<password> ;
    #
    # where you replace <host>, <user>, <password> by quoted strings and
    # <port> by the master's port number (3306 by default).
    #
    # Example:
    #
    # CHANGE MASTER TO MASTER_HOST='125.564.12.1', MASTER_PORT=3306,
    # MASTER_USER='joe', MASTER_PASSWORD='secret';
    #
    # OR
    #
    # 2) Set the variables below. However, in case you choose this method, then
    # start replication for the first time (even unsuccessfully, for example
    # if you mistyped the password in master-password and the slave fails to
    # connect), the slave will create a master.info file, and any later
    # change in this file to the variables' values below will be ignored and
    # overridden by the content of the master.info file, unless you shutdown
    # the slave server, delete master.info and restart the slaver server.
    # For that reason, you may want to leave the lines below untouched
    # (commented) and instead use CHANGE MASTER TO (see above)
    #
    # required unique id between 2 and 2^32 - 1
    # (and different from the master)
    # defaults to 2 if master-host is set
    # but will not function as a slave if omitted
    #server-id = 2
    #
    # The replication master for this slave - required
    #master-host = <hostname>
    #
    # The username the slave will use for authentication when connecting
    # to the master - required
    #master-user = <username>
    #
    # The password the slave will authenticate with when connecting to
    # the master - required
    #master-password = <password>
    #
    # The port the master is listening on.
    # optional - defaults to 3306
    #master-port = <port>
    #
    # binary logging - not required for slaves, but recommended
    #log-bin=mysql-bin
    #
    # binary logging format - mixed recommended
    #binlog_format=mixed

    # Uncomment the following if you are using InnoDB tables
    #innodb_data_home_dir = /var/lib/mysql
    #innodb_data_file_path = ibdata1:2000M;ibdata2:10M:autoextend
    #innodb_log_group_home_dir = /var/lib/mysql
    # You can set .._buffer_pool_size up to 50 - 80 %
    # of RAM but beware of setting memory usage too high
    #innodb_buffer_pool_size = 384M
    #innodb_additional_mem_pool_size = 20M
    # Set .._log_file_size to 25 % of buffer pool size
    #innodb_log_file_size = 100M
    #innodb_log_buffer_size = 8M
    #innodb_flush_log_at_trx_commit = 1
    #innodb_lock_wait_timeout = 50

    [mysqldump]
    quick
    max_allowed_packet = 16M

    [mysql]
    no-auto-rehash
    # Remove the next comment character if you are not familiar with SQL
    #safe-updates

    [myisamchk]
    key_buffer_size = 256M
    sort_buffer_size = 256M
    read_buffer = 2M
    write_buffer = 2M

    [mysqlhotcopy]
    interactive-timeout




    My server is VPS Quad Core 3 gb ram
     
  2. arunsv84

    arunsv84 Well-Known Member

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    You need to check the I/O first. Normally with virtual servers, I/O seems to be a problem. Also check if table locking is there. Just issue the following command to see the results.

    If that returns lots of queries waiting for table lock, then you can confirm that table locking is causing the issue. If it is a busy forum and you see a lot of slow queries, the MySQL server will clog up, become very slow and eventually will lock the tables.

    If you see lots of "copying to tmp table" in process list, you may want to tweak my.cnf to allow a larger tmp_table size, though it consume RAM.

    Its recommended to convert the databases to InnoDB and it will solve lot of problems related to SMF forums.

    If the memory & I/O is fine, then you need to check the MySQL process and make sure that there is no other things are eating the resources.

    You can also use cPnginx : cPanel Nginx plugin - Turbo boost your cPanel server with high stability, as it is easy to setup and configure from WHM.

    Cheers!!!
     
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