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This page describes how to connect Stash to a MySQL database.
MySQL performance issues
MySQL, while supported by Stash, is currently not recommended especially in larger instances, due to inherent performance and deadlock issues that occur in this database engine under heavy load.
Affected systems may experience slow response times, deadlock errors and in extreme cases errors due to running out of database connections. These issues are intrinsic to MySQL (no other database engine in Stash's Supported platforms shares this behavior) and are due to the way MySQL performs row-level locking in transactions. See http://dev.mysql.com/doc/refman/5.0/en/innodb-deadlocks.html for some general information on this.
Stash does its best to work around the MySQL behavior - see issues STASH-4517, STASH-4701 and others for example. However, under very heavy load you will generally get better performance with any of the other database engines supported by Stash (such as PostgreSQL which is also freely available) than you will with MySQL. Please see Connecting Stash to an external database for instructions on migrating your data to one of these other engines.
MySQL 5.6.x Compatibility
See Supported platforms for the versions of MySQL supported by Stash.
The overall process for using a MySQL database with Stash is:
Before you can use Stash with MySQL, you must set up the MySQL server as follows:
Create a database on MySQL for Stash to use.
|Create database user|
Create a Stash user on the database.
Configure the database to use
Note that Stash on MySQL does not support 4 byte UTF-8 characters.
Configure the database to use
If MySQL is using binary logging, configure the database to use a binary logging format of either
Refer to the MySQL documentation. Note that Stash sets the MySQL transaction isolation level to
Stash requires the database to keep idle connections alive for at least 10 minutes.
If the database is configured with less than a 10 minute connection timeout, there will be seemingly random connection errors.
Here is an example of how to do that. When Stash and MySQL run on the same physical computer (accessible through
localhost), run the following commands (replacing
password with your own values):
This creates an empty MySQL database with the name
stash, and a user that can log in from the host that Stash is running on who has full access to the newly created database. In particular, the user should be allowed to create and drop tables, indexes and other constraints.
If the MySQL database and Stash servers are on the same physical computer, you can use
localhost and not set a password by omitting
IDENTIFIED BY 'password' from the 2nd MySQL statement above (if you trust the security within this computer).
If the MySQL database and Stash servers are on different computers, just replace the
localhost part of the GRANT ALL statement above with the hostname of the machine that Stash is running on. See the documentation at http://dev.mysql.com/doc/refman/5.1/en/account-names.html.
Note that Stash will generally require about 25–30 connections to the database. The maximum number of connections is a configurable system property – see Database pool.
The JDBC drivers for MySQL are not bundled with Stash (due to licensing restrictions). You need to download and install the driver yourself, after you have installed Stash.
<Stash home directory>/libdirectory (for Stash 2.1 or later).
You can migrate Stash to the MySQL database created above, either from the embedded database or from another external database.
Run the migration as follows:
See these notes about database migration.
The host name or IP address of the computer running the database server.
|Port||The TCP port with which Stash can connect to the database server. The default value is the default port that MySQL runs against. You can change that if you know the port that your MySQL instance is using.|
|Database name||The name of the database that Stash should connect to.|
|Database username||The username that Stash should use to access the database.|
|Database password||The password that Stash should use to access the database.|