Merge "Added a procedure and edits to HA guide"
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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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