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cron job to kill slow query issue

Discussion in 'Workarounds and Optimization' started by fancier, Jul 19, 2013.

  1. fancier

    fancier Member

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    Code:
    <?php

$con = mysql_connect( "localhost", "user", "pass" ) or die( "can not connect" );
if( $con ) echo "Connected<br>";

$result = mysql_query( "SHOW FULL PROCESSLIST", $con );
while( $row = mysql_fetch_array( $result, $con ) )
{

    $process_id = $row["id"];
    if ($row["Time"] > 100 )
    {
        $sql = "KILL $process_id";
        $res = mysql_query( "$sql", $con );
        if( $res )
        {
            echo "Mysql Process ID $process_id has been killed<br>";
        }
    }
    else echo "Row not found?<br>";
}
?>
    I tried this code for cron job to kill slow query

    but when i run this cron.php then i got this error

    Connected

    Warning: mysql_fetch_array() expects parameter 2 to be long, resource given in /home/r/public_html/da/cron.php on line 7
     
    #1 fancier, Jul 19, 2013
  2. STS Admin

    STS Admin Well-Known Member

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    In the below line the second parameter is type of array that is to be fetched not $con. It's a constant and can take the following values: MYSQL_ASSOC, MYSQL_NUM, and MYSQL_BOTH.

     
    #2 STS Admin, Jul 19, 2013
  3. fancier

    fancier Member

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    So guide what change i have to made, my issue is that on high traffic too many slow queries take place that hangs mysql

    I have SMF 2.0.4 default theme
     
    #3 fancier, Jul 20, 2013
  4. thinkbot

    thinkbot Well-Known Member

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    if you got slow queries, post your my.cnf config, hardware spec etc and mysqltuner result
     
    #4 thinkbot, Jul 20, 2013
  5. fancier

    fancier Member

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    Code:
    [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
open_files_limit = 10000
query_cache_size = 32M
query_cache_size = 512M
max_heap_table_size = 16M
table_cache = 400
max_connections = 100
thread_cache_size = 286
interactive_timeout = 25
wait_timeout = 100
connect_timeout = 10
max_connect_errors = 10
query_cache_type = 1
tmp_table_size = 64M
join_buffer_size = 2M
net_buffer_length = 2K
thread_stack = 64K
low_priority_updates=1
concurrent_insert=ALWAYS
long_query_time = 0.1
slow_query_log = 1
slow_query_log_file = /var/log/mysql-slow-query.log
slow_query_log_microseconds_timestamp = 1
log_queries_not_using_indexes = 1
innodb_data_home_dir = /var/lib/mysql
innodb_data_file_path = ibdata1:2000M;ibdata2:10M:autoextend
innodb_log_group_home_dir = /var/lib/mysql
innodb_buffer_pool_size = 384M
innodb_additional_mem_pool_size = 20M
innodb_log_file_size = 100M
innodb_log_buffer_size = 8M
innodb_flush_log_at_trx_commit = 1
innodb_lock_wait_timeout = 50

[mysql]
no-auto-rehash


[mysqlhotcopy]
interactive-timeout

port = 3306
socket = /var/lib/mysql/mysql.sock


[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
    I have four quad CPU and 3 gb RAM VPS Server, when load is high then too many tables got open, some running, some lock, I see those here /http://realinfo.tv/status.php
     
    #5 fancier, Jul 20, 2013
  6. thinkbot

    thinkbot Well-Known Member

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    and mysqltuner please
     
    #6 thinkbot, Jul 20, 2013
  7. fancier

    fancier Member

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    I did install it yet

    please guide if I change

    innodb_lock_wait_timeout = 50
    long_query_time = 0.1
    wait_timeout = 100
    max_connections = 100


    then it can be useful to decrease load that occur by mysql
     
    #7 fancier, Jul 20, 2013
    Last edited: Jul 20, 2013
  8. fancier

    fancier Member

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    I got that data, now please guide me

    -------- General Statistics --------------------------------------------------
    [--] Skipped version check for MySQLTuner script
    [OK] Currently running supported MySQL version 5.1.70-cll
    [OK] Operating on 64-bit architecture

    -------- Storage Engine Statistics -------------------------------------------
    [--] Status: +Archive -BDB -Federated +InnoDB -ISAM -NDBCluster
    [--] Data in MyISAM tables: 1G (Tables: 397)
    [--] Data in InnoDB tables: 32M (Tables: 75)
    [--] Data in MEMORY tables: 1M (Tables: 1)
    [!!] Total fragmented tables: 92

    -------- Security Recommendations -------------------------------------------
    [OK] All database users have passwords assigned

    -------- Performance Metrics -------------------------------------------------
    [--] Up for: 4d 17h 23m 45s (14M q [34.378 qps], 635K conn, TX: 50B, RX: 3B)
    [--] Reads / Writes: 64% / 36%
    [--] Total buffers: 442.0M global + 12.4M per thread (151 max threads)
    [OK] Maximum possible memory usage: 2.3G (76% of installed RAM)
    [OK] Slow queries: 0% (3K/14M)
    [!!] Highest connection usage: 100% (152/151)
    [OK] Key buffer size / total MyISAM indexes: 384.0M/105.0M
    [OK] Key buffer hit rate: 100.0% (2B cached / 221K reads)
    [OK] Query cache efficiency: 55.5% (5M cached / 9M selects)
    [!!] Query cache prunes per day: 77385
    [OK] Sorts requiring temporary tables: 0% (0 temp sorts / 255K sorts)
    [OK] Temporary tables created on disk: 7% (5K on disk / 77K total)
    [OK] Thread cache hit rate: 99% (1K created / 635K connections)
    [!!] Table cache hit rate: 2% (512 open / 19K opened)
    [OK] Open file limit used: 7% (788/10K)
    [OK] Table locks acquired immediately: 99% (11M immediate / 11M locks)
    [!!] InnoDB data size / buffer pool: 32.4M/8.0M

    -------- Recommendations -----------------------------------------------------
    General recommendations:
    Run OPTIMIZE TABLE to defragment tables for better performance
    Enable the slow query log to troubleshoot bad queries
    Reduce or eliminate persistent connections to reduce connection usage
    Increase table_cache gradually to avoid file descriptor limits
    Variables to adjust:
    max_connections (> 151)
    wait_timeout (< 28800)
    interactive_timeout (< 28800)
    query_cache_size (> 32M)
    table_cache (> 512)
    innodb_buffer_pool_size (>= 32M)
     
    #8 fancier, Jul 21, 2013
  9. thinkbot

    thinkbot Well-Known Member

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    You got very little tables actually,
    Your table cache ratio is small becouse probably many temporary tables in memory, and 7% on disk (which could be optimized)
    But don't worry about table cache ratio, that's not a problem

    I would suggest adjusting settings as below:
    table_open_cache = 1000
    sort_buffer_size = 256K
    read_buffer_size = 128K
    read_rnd_buffer_size = 4M
    thread_cache_size = 20

    thread_cache_size = 286 - remove that, its doubled
    table_cache = 400 - remove that, its the same as table_open_cache

    query_cache_size = 32M
    query_cache_size = 512M

    remove 2 lines of that, leave one
    query_cache_size = 30M

    connect_timeout = 2

    join_buffer_size = 1M

    net_buffer_length = 2K - remove that
    thread_stack = 64K - remove that
    low_priority_updates=1 - remove that
    concurrent_insert=2

    innodb_buffer_pool_size = 384M - this is good, but mysqltuner shows 8M, so it seems like you didnt restart mysql yet after chaning those in my.cnf
    innodb_flush_log_at_trx_commit = 2
    innodb_lock_wait_timeout = 50 - remove that


    when it comes to slow queries
    wget http://percona.com/get/pt-query-digest
    chmod +x pt-query-digest
    ./pt-query-digest /var/log/mysql-slow-query.log > slow.txt

    and copy them here for review
     
    #9 thinkbot, Jul 21, 2013
    Last edited: Jul 21, 2013
  10. thinkbot

    thinkbot Well-Known Member

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    status.php shows different values, so it seems like server wasn't restarted after last my.cnf changes


    your current slow log is in
    /var/lib/mysql/server-slow.log
    so

    ./pt-query-digest /var/lib/mysql/server-slow.log > slow.txt

    its good to keep that

    slow_query_log_file = server-slow.log

    innodb_buffer_pool_size in current settings from status.php is 8MB

    long_query_time is 10s :|
    horrible, run pt-query-digest and we wil lsee that slow queries
     
    #10 thinkbot, Jul 21, 2013
  11. cPanelMichael

    cPanelMichael Forums Analyst
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    Hello :)

    Yes, finding the reason for the slow query or tuning your MySQL configuration is a much better solution than setting up a cron job to kill them. You risk killing legitimate MySQL processes with such a cron job.

    Thank you.
     
    #11 cPanelMichael, Jul 22, 2013
  12. fancier

    fancier Member

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    When i try above my.cnf then I got "The MySQL® server is currently offline. "

    guide where is varable wrong that made "The MySQL® server is currently offline. "

    Mysql works when i put blank my.cnf

    Please guide
     
    #12 fancier, Jul 22, 2013
  13. fancier

    fancier Member

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    Actually I just dont have much knowledge about MYSQL, so I don't able to understand why it got hang in high traffic

    One more strange thing is that it normally hang near about 6:30 pm Indian Time

    So i'm thinking to have cronjob to save mysql from hanging
    thanks
     
    #13 fancier, Jul 22, 2013
  14. thinkbot

    thinkbot Well-Known Member

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    so you had blank my.cnf previously, or default, not the one you copied

    run this
    Code:
    [mysqld]
skip-external-locking
skip-name-resolve
myisam_use_mmap=1

key_buffer_size = 384M
table_open_cache = 1000
sort_buffer_size = 256K
read_buffer_size = 128K
read_rnd_buffer_size = 4M
thread_cache_size = 20

myisam_sort_buffer_size = 64M
query_cache_size = 30M
max_heap_table_size = 50M
max_connections = 100
wait_timeout = 60
connect_timeout = 2

query_cache_type = 1
tmp_table_size = 64M
join_buffer_size = 1M

concurrent_insert=2

slow_query_log=1
slow_query_log_file=mysql-slow.log
long_query_time=0.1		
log_queries_not_using_indexes = 1

innodb_buffer_pool_size = 384M
innodb_additional_mem_pool_size = 20M
innodb_log_file_size = 100M
innodb_log_buffer_size = 8M
innodb_flush_log_at_trx_commit = 2
    and run pt-query-digest before as wrote
    ./pt-query-digest /var/lib/mysql/server-slow.log > slow.txt

    and copy here slow.txt
     
    #14 thinkbot, Jul 22, 2013
    Last edited: Jul 22, 2013
  15. fancier

    fancier Member

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    Now i have blank my.cnf

    Previously I have default my.cnf

    when I try above variables in my.cnf and reboot server then I got "The MySQL® server is currently offline. "

    Sir my issue is that on high traffic too many tables got open(some running, some sleeping, some locked), that we can see at Server Status it's like Total processes: 146 (10 sleeping, 121 running, 10 locked)


    If i can have some cronjob that check after 1 min or five min and see if there are too many Total Process then it can kill all query of mysql

    please guide or make a cronjob php for me that can do what i needed
     
    #15 fancier, Jul 23, 2013
  16. thinkbot

    thinkbot Well-Known Member

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    Please copy here last 100 lines from error log of mysql

    tail -n 100 /var/lib/mysq/*.err

    to see which variable it doesnt accept



    ----
    Your problem is slow execution of queries, part becouse of not optimized settings, second becouse of queries using temporary tables (means not optimized, slow queries; maybe even not using indexes)
     
    #16 thinkbot, Jul 23, 2013
  17. fancier

    fancier Member

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    these are error

    please give some solution
     
    #17 fancier, Jul 23, 2013
  18. thinkbot

    thinkbot Well-Known Member

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    ok, update my.cnf to the one that I proposed, then run

    rm -rf /var/lib/mysql/ib_logfile*;
    restart mysql

    then run mysqlcheck -r eximstats;

    (since eximstats database seems to be broken)

    you can add to my.cnf after myisam_sort_buffer_size = 64M
    myisam_recover = BACKUP, FORCE
    to have automatic repair, when some MyISAM table breaks

    after restarting mysql, let it run for some time, and make mysqltuner results again
    and run
    cd /root;
    wget http://percona.com/get/pt-query-digest
    chmod +x pt-query-digest
    ./pt-query-digest /var/lib/mysql/server-slow.log > slow.txt

    to review slow queries
    you can then copy slow.txt here
     
    #18 thinkbot, Jul 23, 2013
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