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Showing entries 1 to 30 of 72 Next 30 Older Entries

Displaying posts with tag: configuration (reset)

Configuring MySQL to use minimal memory
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I’ve been experimenting with MySQL Fabric – the official tool in development to provide HA and sharding. Part of this experimentation has meant that I have been running 7 copies of the MySQL Server on my laptop at once, which can consume a lot of memory

So today I wanted to write about how to configure MySQL to use less memory, which may also be beneficial in situations where peak performance is not important. For example: a developer VM environment.

Previous configuration guides

Before I get started, let me point to some of my previous configuration guides:

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How to Enable MySQL Event Scheduler
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You may think that you already know what's the opposite of "DISABLED", but with MySQL Event Scheduler you'll be wrong.

In fact MySQL Event Scheduler may have three different states[1][2]:

DISABLED -  The Event Scheduler thread does not run [1]. In addition, the Event Scheduler state cannot be changed at runtime.
OFF (default) - The Event Scheduler thread does not run [1]. When the Event Scheduler is OFF it can be started by setting the value of event_scheduler to ON.
ON - The Event Scheduler is started; the event scheduler thread runs and executes all scheduled events.

So if you're going to find it in the DISABLED state and instinctively set it to ENABLED you'll end up with a non-starting MySQL daemon.
Be warned and stay safe out there!


[1]: http://dev.mysql.com/doc/refman/5.5/en/events-configuration.html
[2]: When the Event Scheduler is not running does not appear in the output of SHOW PROCESSLIST
TokuDB configuration variables of interest
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During our experiments I came upon a few TokuDB variables of interest; if you are using TokuDB you might want to look into these:

  • tokudb_analyze_time

This is a boundary on the number of seconds an ANALYZE TABLE will operate on each index on each partition on a TokuDB table.

That is, if tokudb_analyze_time = 5, and your table has 4 indexes (including PRIMARY) and 7 partitions, then the total runtime is limited to 5*4*7 = 140 seconds.

Default in 7.1.0: 5 seconds

  • tokudb_cache_size

Similar to innodb_buffer_pool_size, this variable sets the amount of memory allocated by TokuDB for caching pages. Like InnoDB the table is clustered within

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Understanding gcache in Galera
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October 16, 2013 By Severalnines

Galera uses a preallocated file with a specific size called gcache, used to store the writesets in circular buffer style. By default, its size is 128MB. In this post, we are going to explore how to leverage gcache to improve the operation of a Galera cluster.

 

Test Case

 

We have a four node Galera cluster, using the latest release 23.2.7(r157). We have a table called t1 that is replicated by Galera on all nodes. The cluster nodes have allocated the default 128MB gcache.size, and we’ll try to execute a large writeset to see how gcache responds.

mysql> 
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On MySQL plugin configuration
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MySQL offers plugin API, with which you can add different types of plugins to the server. The API is roughly the same for all plugin types: you implement an init() function, a deinit(); you declare status variables and global variables associated with your plugin, and of course you implement the particular implementation of plugin call.

I wish to discuss the creation and use of global variables for plugins.

Consider the following declaration of a global variable in audit_login:

static MYSQL_SYSVAR_BOOL(enabled, plugin_enabled, PLUGIN_VAR_NOCMDARG,
"enable/disable the plugin's operation, namely writing to file", NULL, NULL, 1);

static struct
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How to Scale Joomla on Multiple Servers
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July 2, 2013 By Severalnines

Joomla! is estimated to be the second most used CMS on the internet after WordPress, with users like eBay, IKEA, Sony, McDonald’s and Pizza Hut. In this post, we will describe how to scale Joomla on multiple servers. This architecture not only allows the CMS to handle more users, by load-balancing traffic across multiple servers. It also brings high availability by providing fail-over between servers.

 

This post is similar to our previous posts on web application scalability and high availability:

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Some new (and useful!!) MySQL 5.6 variables
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Upgrading from MySQL 5.5 to MySQL 5.6 is a fairly straightforward process. However, the move to version 5.6 does bring with it some new varaibles with which to work.

One of the recent innovations (pioneered by Percona in Percona Server 5.5 if I recall correctly) is the ability to "dump" the innodb buffer pool***. This can be done any time MySQL is running and can be configured to be executed during MySQL shutdown. One reason to do this is to have a server "pre-warmed" when you perform a server restart. Why this is important is that during server operation the innodb buffer pool will fill up. Typically the server will operate much better when this buffer pool is full instead of being empty or paritally full because the return of data from the buffer pool is much faster than returning data from disk. 

There are four important variables with each

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Scaling Wordpress and MySQL on Multiple Servers for Performance
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June 11, 2013 By Severalnines

Over the years, WordPress has evolved from a simple blogging platform to a CMS. Over seven million sites use it today, including the likes of CNN, Forbes, The New York Times and eBay. So, how do you scale Wordpress on multiple servers for high performance? 

 

This post is similar to our previous post on Drupal, Scaling Drupal on Multiple Servers with Galera Cluster for MySQL but we will focus on Wordpress, Percona XtraDB Cluster and GlusterFS using Debian Squeeze 64bit.

read more

MySQL updates, openSUSE 13.1 and default configuration
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Recently I had some time to do some clenaups/changes/updates in server:database repo regarding MySQL (and MariaDB). Nothing too big. Well actually, there are few little things that I want to talk about and that is the reason for this blog post, but still, nothing really important…

MySQL 5.5, 5.6 and 5.7

MySQL 5.6 is stable for some time already, so it’s time to put it in the action. So I sent the request to include it in Factory and therefore in openSUSE 13.1. There is off course a list of

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MySQL binlogs - Don't forget to do your homework!
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Now that I'm back doing just database stuff, I've come to realize I've gotten a little sloppy about doing my homework.  Homework's never been my favorite thing in the world, but it often reduces stress when your under the gun during an outage or upgrade... We had a MySQL database server that's been slow on DML changes, and based on the slowest statements being 'COMMIT', we had a good mind
On configuring the Performance Schema
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On configuring the Performance Schema

This article is a user guide about MySQL 5.6 Performance Schema configuration. As with many things, the way to approach problems may vary a lot based on systems, user experiences, or just plain opinions, so the "Your Mileage May Vary" caution applies here.

It is easy to get lost in details, and yet starting with the big picture in mind helps to understand not only how, but also more importantly why, to do things ...

The magic recipe is as follows
  • Define your goals
  • Define what to instrument
  • Define how much detail to collect
  • Provide sizing data
  • Monitor sizing problems

Define your goals
Performance instrumentation in general can be used for many different things, ranging from casual monitoring in production to debugging in








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Do we need a MySQL Cookbook?
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The blog title says it all: Do we need a MySQL Cookbook? I tend to think so.

This seems to be something that is missing with current MySQL documentation. There is lots of information available but finding the appropriate bit can be quite tedious and it often requires looking in multiple places.

A lot of other software has such books, but for some reason MySQL seems to be missing one.

A recent example comes from a “documentation feature request” I posted today: http://bugs.mysql.com/bug.php?id=68171. MySQL 5.6 provides a way to “move InnoDB tables” from one server to another. There are many reasons why you may want to do it, but the documentation is currently rather sparse. A simple “example recipe” for this would be good, as would an equivalent recipe for other

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Thoughts on MySQL 5.6 new replication features
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After playing a little bit with MySQL 5.6 (RC), and following closely on Giuseppe's MySQL 5.6 replication gotchas (and bugs), I was having some thoughts.

These are shared for a few reasons:

  • Maybe I didn't understand it well, and someone could correct me
  • Or I understood it well, and my input could be of service to the developers
  • Or it could be of service to the users

InnoDB tables in mysql schema

The introduction of InnoDB tables in mysql makes for crash-safe replication information: the exact replication position (master log file+pos, relay log file+pos etc.) is updated on InnoDB tables; with innodb_flush_logs_at_trx_commit=1 this means replication status is

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MySQL 5.6, GTID and performance_schema
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Not much to add really to the bug I’ve filed here: bug#67159.

Again this GTID stuff looks good, but seems to prevent changes in the configuration of performance_schema, which I think is not appropriate, especially as P_S now has lots of extra goodies and after 5.6 will surely have even more.

Help me polish MySQL in openSUSE 12.2
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If you are following news regarding openSUSE and MySQL, you probably already know, that we have both MySQL and MariaDB in openSUSE to allow users to choose what they want to use. And if these two options are not enough, we’ve got server:database repository with newest and greatest development versions of both and MySQL Cluster on to of that. I think all this is great and awesome, that we have all of that.

Now to the not so great part. Unfortunately I’m bare human, I have to eat, sleep and I have some work, some bugs that takes a lot more time that I expected, some school duties to take care of and of course

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What is the proper size of InnoDB logs?
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In one of my previous posts, “How to resize InnoDB logs?”, I gave the advice on how to safely change the size of transaction logs. This time, I will explain why doing it may become necessary.

A brief introduction to InnoDB transaction logs

The transaction logs handle REDO logging, which means they keep the record of all recent modifications performed by queries in any InnoDB table. But they are a lot more than just an archive of transactions. The logs play important part in the process of handling writes. When a transaction commits, InnoDB synchronously makes a note of any changes into the log, while updating the actual table files happens asynchronously and may take place much later. Each log entry is assigned a Log Sequence Number

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The Problems of Managing MySQL’s Configuration
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I want to keep a record of the configuration of the MySQL servers I manage. The configuration of some servers differs from others and over time the configuration may vary, partly as a result of upgrades in the mysql version or the use of the particular mysql instance, so tracking this is important.

Configuration items in MySQL can be thought of in 2 separate parts: the static configuration files which determine the behaviour of the server when it starts up (my.cnf) and the running configuration of the server in question. The latter information is usually obtained by running SHOW GLOBAL VARIABLES and SHOW SLAVE STATUS if the server is a slave.

I’d also like to compare the 2 sets of configuration so I can see if a local change has been made to the running server which is not reflected in its configuration file. I might want to correct this, or

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PuppetConf and the state of devops
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It’s been some time now that we’ve been talking about devops, the pushing together of application development and application deployment via IT operations, in the enterprise. To keep up to speed on the trend, 451 CAOS attended PuppetConf, a conference for the Puppet Labs community of IT administrators, developers and industry leaders around the open source Puppet server configuration and automation software. One thing that seems clear, given the talk about agile development and operations, cloud computing, business and culture, our definition of devops continues to be accurate.

Another consistent part of devops that also emerged at PuppetConf last week was the way it tends to introduce additional stakeholders

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Useful sed / awk liners for MySQL
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Listing some useful sed / awk liners to use with MySQL. I use these on occasion.

sed, awk & grep have many overlapping features. Some simple tasks can be performed by either. For example, stripping empty lines can be performed by either:

grep '.'
awk '/./'
sed '/./!d'
grep -v '^$'
awk '!/^$/'
sed '/^$/d'

It's a matter of taste & convention which tool and variation to use. So for any script I suggest, there may be many variations, possibly cleaner, shorter; feel free to comment.

mysqldump

The output of mysqldump is in particular useful when one wishes to make transformation on data or metadata.

  • Convert
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Recovering a MySQL `root` password: the fourth solution
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Have just read Darren Cassar’s Recovering a MySQL `root` password – Three solutions. There’s a fourth solution: using an init-file, which leads to just one restart of the database instead of two. It also avoids the security issue involved with using skip-grant-tables.

I’ve written all about it before on Dangers of skip-grant-tables.

Darren’s 1st advice (look for password ini files, scripts, etc.) is a very good one. One password that can always be looked up in files is the replication’s password.

Replication’s password is easily forgotten: you only set it once and never use it again; never

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Upgrading passwords from old_passwords to “new passwords”
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You have old_passwords=1 in your my.cnf. I’m guessing this is because you used one of the my-small.cnf, my-large.cnf etc. templates provided with your MySQL distribution.

These files can easily win the “most outdated sample configuration file contest”.

Usually it’s no big deal: if some parameter isn’t right, you just go and change it. Some variables, though, have a long-lasting effect, and are not easily reversed.

What’s the deal with old_passwords?

No one should be using these anymore. This variable makes the password hashing algorithm compatible with that of MySQL 4.0. I’m pretty sure 4.0 was released 9 years ago. I don’t know of anyone still using it (or

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Web and Telco mode Cluster Configuration
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The Core Scripts (aka Configurator) for MySQL Cluster has now been updated with a new feature that allows you to tune cluster for a particular workload.
Currently there are two types of workloads supported:
  • Web
  • Telco/Realtime
The Web workload is suitable for applications:
  • with long running transactions (scans, joins and/or large updates)
  • reading and especially writing of large chunks (BLOBs) of data where an "innodb" like behavior is wanted.
The Telco workload is suitable for realtime



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Cluster/J - Document-oriented approach on MySQL Cluster
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In a project Severalnines is engaged in, we are developing a realtime application based on Cluster/J. To start with, I must say cluster/j is fantastic and so far I am very happy with it and beaten our expectations big time. It is quite new however and we stumbled on a couple of issues, but those were fixed very fast by the Cluster/J developers. The bugs we encountered were:
Both which were worked around, and really we never did need to have a binary or a varbinary as the PK, we used a

Performance is great - we have two data nodes (nehalem, 32GB RAM, 146GB SAS 10K disk, 2x4 core 2.4GHz (E5620) ) and two application hosts (same spec, less RAM as data



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Custom MySQL config files to ensure maximum performance
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The config files that come with MySQL server are generally not that good. They almost never work well for enterprise server loads and will leave most people wondering why the database needs someone to come fix it. In fact that might be why they roll those configs by default, to keep the consulting services alive and profitable. Personally I have no issues with consulting services, but everyone should start out with good configs to begin with. Well, no worries… here are config files for different system RAM configurations. Just choose the one that fits how much RAM your server has and make sure the cnf file is in place before you install the MySQL server RPM/tar/deb packages. Obviously you’ll want to remove the extension of the filename so it reads “my.cnf” and not “my.cnf_64GB” or the like. These cnfs have

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Upgrading to Barracuda & getting rid of huge ibdata1 file
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Some of this is old stuff, but more people are now converting to InnoDB plugin, so as to enjoy table compression, performance boosts. Same holds for people converting to Percona’s XtraDB. InnoDB plugin requires innodb_file_per_table. No more shared tablespace file.

So your ibdata1 file is some 150GB, and it won’t reduce. Really, it won’t reduce. You set innodb_file_per_table=1, do ALTER TABLE t ENGINE=InnoDB (optionally ROW_FORMAT=COMPRESSED KEY_BLOCK_SIZE=8), and you get all your tables in file-per-table .ibd files.

But the original ibdata1 file is still there. It has to be there, don’t delete it! It contains more than your old data.

InnoDB tablespace files never reduce in size,

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Tuning InnoDB Configuration
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I had earlier written a post on tuning the MySQL server configuration which was more geared towards the MyISAM storage engine. While that is not because I didn't intend on ignoring InnoDB but because I had planned a whole post on tuning InnoDB related configuration. So this post is the post that I had planned, I have discussed the major configuration parameters in here that should help you out most of the times.
Where’s my cnf file?
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So you have a running MySQL server, it’s working well and everyone’s happy. You want to make a minor change to the configuration file, so you edit the file, restart MySQL – but the change doesn’t catch!

Or maybe you want to check that some global variable has not been dynamically changed without an update to the configuration file. But the configuration file doesn’t make any sense — it looks like nothing is common between the file and the server.

Wait, which my.cnf file does MySQL read? Rather, which my.cnf files?

Ever happened to you? If you’re well organized, and only keep a single /etc/my.cnf file, you know exactly where everything is. But some systems are messier, with lots of configuration files hanging around. Which ones apply?

Let’s find out

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MySQL terminology: processes, threads & connections
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There’s some confusion in the MySQL terminology for processes, threads & connections, which I will try to resolve. I can’t explain the full nature of what processes and threads are; please see Wikipedia [1] [2] for that. But here’s some basics with regard to MySQL:

  • MySQL server is a single process application.
  • It is multithreaded.
  • It (usually) acts as a TCP/IP server, accepting connections.
  • Each connection gets a dedicated thread.
  • These threads are sometimes named processes, and sometimes they’re referred to as connections.

The last part is where confusion arises, so let me discuss again the use of threads and connections in MySQL.

MySQL

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Tuning MySQL Server Settings
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The default configuration file for MySQL is intended not to use many resources, because its a general purpose sort of a configuration file. The default configuration does enough to have MySQL running happily with limited resources and catering to simple queries and small data-sets. The configuration file would most definitely need to be customized and tuned if you intend on using complex queries and when you have good amount of data. Most of the tunings mentioned in this post are applicable to the MyISAM storage engine, I will soon be posting tunings applicable to the Innodb storage engine. Getting started...
MMM for MySQL single reader role
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The standard documentation and tutorials on MMM for MySQL, for master-master replication setup, suggest one Virtual IP for the writer role, and two Virtual IPs for the reader role. It can be desired to only have a single virtual IP for the reader role, as explained below.

The two IPs for the reader role

A simplified excerpt from the mmm_common.conf sample configuration file, as can be found on the project’s site and which is most quoted:

...
<host db1>
  ip                      192.168.0.11
  mode                    master
  peer                    db2
</host>

<host db2>
  ip                      192.168.0.12
  mode                    master
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Showing entries 1 to 30 of 72 Next 30 Older Entries

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