Added a procedure and edits to HA guide
Added a procedure for the MySQL with Galera page. Also made punctuation changes (commas), and added an extra line of content for the introduction paragraph. Changed procedure from implicit to explicit numbering for impending xml conversion. Change-Id: I9a82e8c945e03eb5a616031559ada026c3548c01 backport: none Closes-Bug: #1319624
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Joseph Robinson
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@ -13,20 +13,28 @@ installations, so we’ll cover it here.
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[[ha-aa-db-mysql-galera]]
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==== MySQL with Galera
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Rather than starting with a vanilla version of MySQL and then adding Galera
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to it, you will want to install a version of MySQL patched for wsrep
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(Write Set REPlication) from https://launchpad.net/codership-mysql/0.7.
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Note that the installation requirements are a bit touchy; you will want
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to make sure to read the README file so you don’t miss any steps.
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Next, download Galera itself from https://launchpad.net/galera/+download.
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Go ahead and install the *.rpms or *.debs, taking care of any dependencies
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that your system doesn’t already have installed.
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Rather than starting with a vanilla version of MySQL, and then adding
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Galera, you will want to install a version of MySQL patched for wsrep
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(Write Set REPlication) from https://launchpad.net/codership-mysql/0.7.
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The wsrep API is suitable for configuring MySQL High Availability in
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OpenStack because it supports synchronous replication.
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Once you’ve completed the installation, you’ll need to make a few configuration changes:
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Note that the installation requirements call for careful attention. Read
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the guide https://launchpadlibrarian.net/66669857/README-wsrep
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to ensure you follow all the required steps.
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In the system-wide +my.conf+ file, make sure mysqld isn’t bound to 127.0.0.1,
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and that +/etc/mysql/conf.d/+ is included. Typically you can find this file at +/etc/my.cnf+:
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Installing Galera through a MySQL version patched for wsrep:
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1. Download Galera from https://launchpad.net/galera/+download, and
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install the *.rpms or *.debs, which takes care of any dependencies
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that your system doesn’t already have installed.
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2. Adjust the configuration:
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In the system-wide +my.conf+ file, make sure mysqld isn’t bound to
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127.0.0.1, and that +/etc/mysql/conf.d/+ is included.
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Typically you can find this file at +/etc/my.cnf+:
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----
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[mysqld]
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@ -36,27 +44,30 @@ and that +/etc/mysql/conf.d/+ is included. Typically you can find this file at +
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#bind-address = 127.0.0.1
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----
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When adding a new node, you must configure it with a MySQL account that can access the
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other nodes so that it can request a state snapshot from one of those existing nodes. First specify
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that account information in +/etc/mysql/conf.d/wsrep.cnf+:
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When adding a new node, you must configure it with a MySQL account that
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can access the other nodes. The new node must be able to request a state
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snapshot from one of the existing nodes:
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3. Specify your MySQL account information in +/etc/mysql/conf.d/wsrep.cnf+:
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----
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wsrep_sst_auth=wsrep_sst:wspass
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----
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Next connect as root and grant privileges to that user:
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4. Connect as root and grant privileges to that user:
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----
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$ mysql -e "SET wsrep_on=OFF; GRANT ALL ON *.* TO wsrep_sst@'%' IDENTIFIED BY 'wspass'";
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----
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You’ll also need to remove user accounts with empty usernames, as they cause problems:
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5. Remove user accounts with empty usernames because they cause problems:
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----
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$ mysql -e "SET wsrep_on=OFF; DELETE FROM mysql.user WHERE user='';"
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----
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You'll also need to set certain mandatory configuration options within MySQL itself. These include:
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6. Set up certain mandatory configuration options within MySQL itself.
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These include:
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----
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query_cache_size=0
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@ -66,29 +77,36 @@ innodb_autoinc_lock_mode=2
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innodb_doublewrite=1
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----
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Finally, make sure that the nodes can access each other through the firewall. This might
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mean adjusting iptables, as in:
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7. Check that the nodes can access each other through the firewall.
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Depending on your environment, this might mean adjusting iptables, as in:
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----
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# iptables --insert RH-Firewall-1-INPUT 1 --proto tcp --source <my IP>/24 --destination <my IP>/32 --dport 3306 -j ACCEPT
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# iptables --insert RH-Firewall-1-INPUT 1 --proto tcp --source <my IP>/24 --destination <my IP>/32 --dport 4567 -j ACCEPT
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----
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It might also mean configuring any NAT firewall between nodes to allow direct connections,
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or disabling SELinux or configuring it to allow mysqld to listen to sockets at unprivileged
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ports.
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This might also mean configuring any NAT firewall between nodes to allow
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direct connections. You might need to disable SELinux, or configure it to
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allow mysqld to listen to sockets at unprivileged ports.
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Now you’re ready to actually create the cluster.
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Now you’re ready to create the cluster.
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===== Create the cluster
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In creating a cluster, you first start a single instance, which creates the cluster. The rest of the MySQL instances then connect to that cluster. For example, if you started on +10.0.0.10+ by executing the command:
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In creating a cluster, you first start a single instance, which creates
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the cluster. The rest of the MySQL instances then connect to
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that cluster:
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An example of creating the cluster:
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1. Start on +10.0.0.10+ by executing the command:
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----
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# service mysql start wsrep_cluster_address=gcomm://
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----
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you could then connect to that cluster on the rest of the nodes by referencing the address of that node, as in:
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2. Connect to that cluster on the rest of the nodes by referencing the
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address of that node, as in:
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----
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# service mysql start wsrep_cluster_address=gcomm://10.0.0.10
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@ -97,8 +115,11 @@ you could then connect to that cluster on the rest of the nodes by referencing t
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You also have the option to set the +wsrep_cluster_address+ in the
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+/etc/mysql/conf.d/wsrep.cnf+ file, or within the client itself. (In
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fact, for some systems, such as MariaDB or Percona, this may be your
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only option.) For example, to check the status of the cluster, open
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the MySQL client and check the status of the various parameters:
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only option.)
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An example of checking the status of the cluster.
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1. Open the MySQL client and check the status of the various parameters:
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----
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mysql> SET GLOBAL wsrep_cluster_address='<cluster address string>';
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@ -162,7 +183,7 @@ mysql> show status like 'wsrep%';
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==== Other ways to provide a highly available database
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MySQL with Galera is by no means the only way to achieve database HA. MariaDB
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(https://mariadb.org/) and Percona (http://www.percona.com/) also work with Galera.
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You also have the option to use Postgres, which has its own replication, or some
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other database HA option.
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MySQL with Galera is by no means the only way to achieve database HA.
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MariaDB (https://mariadb.org/) and Percona (http://www.percona.com/)
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also work with Galera. You also have the option to use Postgres, which
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has its own replication, or another database HA option.
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