I don't know what's going on. My server has been fine for probably a year. Now I'm having a severe problem with MariaDB/MySQL. The DB server keeps crashing. When it does and I bring it back online I get errors, several tables are marked crashed and I have to repair them. Here are the server specs...
CloudLinux Server release 6.6 installed on Centos 6.5 (x64)
WHM/Cpanel 11.50.1 Build 1 (Current)
MariaDB 10.0.21
RAM: 3,820MB (3750MB+ in use)
Swap: 1,023MB (1,023MB in use)
4 Cores (Low idle load)
Available Disk Space: 26GB
I suspect it has to do with memory. Here's a memory alert I get in WHM:
Here's what I get when I try to visit a web site on my server that uses MySQL (As expected):
Warning: mysql_connect(): Connection refused in /home/mysite/public_html/index.php on line 19
Unable to connect to server.
Here's a link to the main error log of my database server (Too much to post here): http://wikisend.com/download/182056/proton.myserver.com.err.txt
This is what happens when I restart my database server from WHM. Each time I restart the db server, random tables are marked as crashed. Sometimes a lot of tables, sometimes just a few and then I have to repair them:
Here is the contents of the /etc/my.cnf file:
root#proton [~]# cat /etc/my.cnf
[mysqld]
default-storage-engine=MyISAM
innodb_file_per_table=1
max_allowed_packet=268435456
open_files_limit=10000
innodb_buffer_pool_size=123731968
The only thing I've tried to fix this is setting this option in WHM:
I only have a handful of sites on the server. Any help is greatly appreciated.
SHOW VARIABLES LIKE '%buffer%';
Do you have other products running in the same VM/server? How much of the 3750MB are they using? Consider increasing RAM as a quick fix. Otherwise, lets look for what is chewing up RAM.
You are probably no using any InnoDB tables? If not then change this to 0:
innodb_buffer_pool_size=123731968
For MyISAM, the most important factor is key_buffer_size; it should be no more than about 500M for your case.
What is WHM?
Abrupt stops of mysql (for any reason) leads to the need to REPAIR MyISAM tables ("marked crashed"). (Consider moving to InnoDB to avoid this recurring nuisance.)
Related
I have setup with Linux, Debian Jessie with Mysql 5.7.13 installed.
I have set following settings in
my.cnf: default_storage_engine= innodb, innodb_buffer_pool_size= 44G
When I start MySQL I manually set max_connections with SET GLOBAL max_connections = 1000;
Then I trigger my loadtest that sends a lot of traffic to the DB server which mostly consists of slow/bad queries.
The result I expected was that I would reach close to 1000 connections but somehow MySQL limits it to 462 connections and I can not find the setting that is responsible for this limit. We are not even close to maxing out the CPU or Memory.
If you have any idea or could point me in a direction where you think the error might be it would be really helpful.
What loadtest did you use? Are you sure that it can utilize about thousands of connections?
You may maxing out your server resources in the disk IO area, especially if you're talking about lot of slow/bad queries. Did you check for disk utilization on your server?
Even if your InnoDB pool size is large your DB still need to read your DB to the cache first, and if your entire DB is large it will not help you.
I can recommend you to perform such a test once more time and track your disk performance during loadtest using iostat or iotop utility.
Look here for more examples of the server performance troubleshooting.
I found the issue, it was du to limitation of Apache server, there is a "hidden" setting inside /etc/apache2/mods-enabled/mpm_prefork.conf which will overwrite setting inside /etc/apache2/apache2.conf
Thank you!
I have a problem with my unix server. This started a week ago. One day after a backup (I used to keep 3 backup files) I visited a website on the server but it wouldn't work. I restarted the server and it seemed to be working fine except the mysql service. My attempts to restart it failed. Then I figured that was because the server was full, so I deleted one of the backups, cleaned up some space and the mysql service restarted successfully. Than I figured tables in one of the databases (MYIsam tables) were corrupt. So I repaired them through myisamchk command via ssh and all worked fine. However, the very next day I woke up they were corrupt again (despite mysql was working fine), and this time there was no disk space problem on the server. I repaired them again. The next day the same thing happenned; and this time innodb tables that were part of another database were corrupt as well. I've fixed them too, so now all is working well but I guess the same thing will happen after tonight's backup.
I can't identify the problem and I don't know what logs to look into to understand the problem. Can anyone please help me out? Thanks very much in advance.
No easy answer here. My immediate thought is that the dbase is still busy when the backups commence, possibly corrupting indexes, interferring with caches, etc. Turn on full logging and check for problems when the backup starts happens. Maybe you will find something.
Look for the my.cnf file. On my CentOs it is located in /etc/my.cnf. It will have a config setting for the location of the error log.
My strongest suspect is OOM kill by the kernel or some other issue that results from running the system out of memory. Try this:
Start top on the server and press M to sort by memory so the biggest memory user is at the top.
note the pid of mysqld
manually perform the backup as you observe the value of the RES column in the top output (resident memory size)
once the backup is over see if the pid of mysqld has changed
If the pid has changed (meaning restart took place), and you saw the memory footprint of mysqld take up something comparable to the total amount of system memory, then my suspicion is correct, and we need to lower some settings in my.cnf to make it use less memory, e.g key_buffer_size and innodb_buffer_pool_size.
EDIT - From the log you posted, there are additional issues although it is not clear how they could be contributing to the table corruption. Your server appears to be running with --skip-innodb and your backup script is not able to deal with the absence of InnoDB storage engine printing exception error messages, but nevertheless continuing. It is also attempting to do a repair, which is failing due to the lack of system privileges (error 1 is Operation not permitted). It is possible that encountering those errors triggers some faulty logic in your backup script that leaves the tables corrupted.
At this point I would recommend disabling MySQL backup using the cPanel tool, and using mysqldump or some other solution (e.g. Xtrabackup (https://www.percona.com/doc/percona-xtrabackup/2.3/index.html)) from a cron job instead.
EDIT2 - from the test results. The manual backup does not run the system out of memory and does not crash the server. The jury is still out on the automatic one.
Don't kill mysqld; shut it down gracefully.
Switch from MyISAM to InnoDB; the latter does not suffer from that 'error'.
The below command takes 2-3 seconds in a Linux MySQL 5.6 server running Php 5.4
exec("mysql --host=$db_host --user=$db_user --password=$db_password $db_name < $sql_file");
On windows with similar configuration it takes 10-15 seconds. The windows machine has a lot more ram (16gb) and similar hard drive. I installed MySQL 5.6 and made no configuration changes. This is on windows server 2012.
What are configurations I can change to fix this?
The database file creates about 40 innodb tables with very minimal inserts.
EDIT: Here is the file I am running:
https://www.dropbox.com/s/uguzgbbnyghok0o/database_14.4.sql?dl=0
UPDATE: On windows 8 and 7 it was 3 seconds. But on windows server 2012 it is 15+ seconds. I disabled System center 2012 and that made no difference.
UPDATE 2:
I also tried killing almost every service except for mysql and IIS and it still performed slowly. Is there something in windows server 2012 that causes this to be slow?
Update 3
I tried disable write cache buffer flush and performance is now great.
I didn't have to do this on other machines I tested with. Does this indicate a bottleneck With how disk is setup?
https://social.technet.microsoft.com/Forums/windows/en-US/282ea0fc-fba7-4474-83d5-f9bbce0e52ea/major-disk-speed-improvement-disable-write-cache-buffer-flushing?forum=w7itproperf
That is why we call it LAMP stack and no doubt why it is so popular mysql on windows vs Linux. But that has more to do more with stability and safety. Performance wise the difference should be minimal. While a Microsoft Professional can best tune the Windows Server explicitly for MySQL by enabling and disabling the services, but we would rather be interested to see the configuration of your my.ini. So what could be the contributing factors w.r.t Windows on MySQL that we should consider
The services and policies in Windows is sometimes a big impediment to performance because of all sorts of restrictions and protections.
We should also take into account the Apache(httpd.conf) and PHP(php.ini) configuration as MySQL is so tightly coupled with them.
Antivirus : Better disable this when benchmarking about performance
Must consider these parameters in my.ini as here you have 40 Innodb tables
innodb_buffer_pool_size, innodb_flush_log_at_trx_commit, query_cache_size, innodb_flush_method, innodb_log_file_size, innodb_file_per_table
For example: If file size of ib_logfile0 = 524288000, Then
524288000/1048576 = 500, Hence innodb_log_file_size should be 500M
innodb_flush_log_at_trx_commit = 2
innodb_flush_method = O_DIRECT
https://dev.mysql.com/doc/refman/5.1/en/innodb-tuning.html
When importing data into InnoDB, make sure that MySQL does not have autocommit mode enabled because that requires a log flush to disk for every insert
SET autocommit=0;
Most importantly innodb_flush_log_at_trx_commit as in this case it is about importing database. Setting this to '2' form '1' (default)hm can be a big performance booster specially during data import as log buffer will be flushed to OS file cache on every transaction commit
For reference :
https://dev.mysql.com/doc/refman/5.5/en/optimizing-innodb-bulk-data-loading.html
https://dba.stackexchange.com/a/72766/60318
http://kvz.io/blog/2009/03/31/improve-mysql-insert-performance/
Lastly, based on this
mysql --host=$db_host --user=$db_user --password=$db_password $db_name < $sql_file
If the mysqldump (.sql) file is not residing in the same host where you are importing, performance will be slow. Consider to copy the (.sql) file exactly in the server where you need to import the database, then try importing without --host option.
Windows is slower at creating files, period. 40 InnoDB tables involves 40 or 80 file creations. Since they are small InnoDB tables, you may as well set innodb_file_per_table=OFF before doing the CREATEs, thereby needing only 40 file creations.
Good practice in MySQL is to create tables once, and not be creating/dropping tables frequently. If your application is designed to do lots of CREATEs, we should focus on that. (Note that, even on Linux, table create time is non-trivial.)
If these are temporary tables... 5.7 will have significant changes that will improve the performance (on either OS) in this area. 5.7 is on the cusp of being GA.
(RAM size is irrelevant in this situation.)
we have a web application (racktables) that's giving us grief on our production box. whenever users try to run a search, it gives the following error:
Pdo exception: PDOException
SQLSTATE[HY000]: General error: 5 Out of memory (Needed 2057328 bytes) (HY000)
I cannot recreate the issue on our backup server. The servers match except for the fact that in production we have 16GB RAM and our backup we have 8GB. It's a moot point though because both are running 32 bit os's and so are only using 4GB of RAM. we also have set up a swap partition...
Here's what i get back from the "free -m" command in production:
prod:/etc# free -m
total used free shared buffers
Mem: 3294 1958 1335 0 118
-/+ buffers: 1839 1454
Swap: 3817 109 3707
prod:/etc#
I've checked to make sure that my.cnf on both boxes match. The database from production was replicated onto the backup server... so the data matches as well.
I guess our options are to:
A) convert the o/s to 64 bit so we can use more RAM.
B) start tweaking some of the innodb settings in my.cnf.
But before I try either A or B, I wanted to know if there's anything else I should compare between the two servers... seeing how the backup is working just fine. There must be a difference somewhere that we are not accounting for.
Any suggestions would be appreciated.
I created a script to simulate load on the backup server and was able to then to recreate the out of memory error message.
In the end, i added the "join_buffer_size" setting to my.cnf and set it 3 MBs. That has resolved the issue.
ps. I downloaded and ran tuning-primer.sh as well as mysqltuner.pl to narrow down the issues.
Recently we changed app server of our rails website from mongrel to passenger [with REE and Rails 2.3.8]. The production setup has 6 machines pointing to a single mysql server and a memcache server. Before each machine had 5 mongrel instance. Now we have 45 passenger instance as the RAM in each machine is 16GB with 2, 4 core cpu. Once we deployed this passenger set up in production. the Website became so slow. and all the request starting to queue up. And eventually we had to roll back.
Now we suspect that the cause should be the increased load to the Mysql server. As before there where only 30 mysql connection and now we have 275 connection. The mysql server has the similar set up as our website machine. bUt all the configs were left to the defaul limit. The buffer_pool_size is only 8 mb though we have 16GB ram. and number of Concurrent threads is 8.
Will this increased simultaneous connection to mysql would have caused mysql to respond slowly than when we had only 30 connections? If so, how can we make mysql perform better with 275 simultaneous connection in place.
Any advice greatly appreciated.
UPDATE:
More information on the mysql server:
RAM : 16GB CPU: two processors each having 4 cores
Tables are innoDB. with only default innodb config values.
Thanks
An idle MySQL connection uses up a stack and a network buffer on the server. That is worth about 200 KB of memory and zero CPU.
In a database using InnoDB only, you should edit /etc/sysctl.conf to include vm.swappiness = 0 to delay swapping out processes as long as possible. You should then increase innodb_buffer_pool_size to about 80% of the systems memory assuming a dedicated database server machine. Make sure the box does not swap, that is, VSIZE should not exceed system RAM.
innodb_thread_concurrency can be set to 0 (unlimited) or 32 to 64, if you are a bit paranoid, assuming MySQL 5.5. The limit is lower in 5.1, and around 4-8 in MySQL 5.0. It is not recommended to use such outdated versions of MySQL in a machine with 8 or 16 cores, there are huge improvements wrt to concurrency in MySQL 5.5 with InnoDB 1.1.
The variable thread_concurrency has no meaning inside a current Linux. It is used to call pthread_setconcurrency() in Linux, which does nothing. It used to have a function in older Solaris/SunOS.
Without further information, the cause for your performance problems cannot be determined with any security, but the above general advice may help. More general advice geared at my limited experience with Ruby can be found in http://mysqldump.azundris.com/archives/72-Rubyisms.html That article is the summary of a consulting job I once did for an early version of a very popular Facebook application.
UPDATE:
According to http://pastebin.com/pT3r6A9q , you are running 5.0.45-community-log, which is awfully old and does not perform well under concurrent load. Use a current 5.5 build, it should perform way better than what you have there.
Also, fix the innodb_buffer_pool_size. You are going nowhere with only 8M of pool here.
While you are at it, innodb_file_per_table should be ON.
Do not switch on innodb_flush_log_at_trx_commit = 2 without understanding what that means, but it may help you temporarily, depending on your persistence requirements. It is not a permanent solution to your problems in any way, though.
If you have any substantial kind of writes going on, you need to review the innodb_log_file_size and innodb_log_buffer_size as well.
If that installation is earning money, you dearly need professional help. I am no longer doing this as a profession, but I can recommend people. Contact me outside of Stack Overflow if you want.
UPDATE:
According to your processlist, you have very many queries in state Sending data. MySQL is in this state when a query is being executed, that is, the main interior Join Loop/Query Execution loop is busy. SHOW ENGINE INNODB STATUS\G will show you something like
...
--------------
ROW OPERATIONS
--------------
3 queries inside InnoDB, 0 queries in queue
...
If that number is larger than say 4-8 (inside InnoDB), 5.0.x is going to have trouble. 5.5.x will perform a lot better here.
Regarding the my.cnf: See my previous comments on your InnoDB. See also my comments on thread_concurrency (without innodb_ prefix):
# On Linux, this does exactly nothing.
thread_concurrency = 8
You are missing all innodb configuration at all. Assuming that you ARE using innodb tables, you are not performing well, no matter what you do.
As far as I know, it's unlikely that merely maintaining/opening the connections would be the problem. Are you seeing this issue even when the site is idle?
I'd try http://www.quest.com/spotlight-on-mysql/ or similar to see if it's really your database that's the bottleneck here.
In the past, I've seen basic networking craziness lead to behaviour similar to what you describe - someone had set up the new machines with an incorrect submask.
Have you looked at any of the machine statistics on the database server? Memory/CPU/disk IO stats? Is the database server struggling?