Creating a Failover Manager cluster

Failover Manager is a high-availability module from EnterpriseDB that enables a Postgres Primary node to automatically failover to a standby node in the event of a software or hardware failure on the primary.

This quick-start guide describes configuring a Failover Manager cluster in a test environment. Read and understand the Failover Manager User Guide before configuring Failover Manager for a production deployment.

Perform these basic installation and configuration steps before starting the tutorial:

  • Install and initialize a database server on one primary and one or two standby nodes. For information about installing Advanced Server, see [EDB Postgres Advanced Server](/epas/latest/) documentation.

  • Postgres streaming replication must be configured and running between the primary and standby nodes. For detailed information about configuring streaming replication, see [PostgreSQL Streaming Replication documentation](https://www.postgresql.org/docs/current/warm-standby.html#STREAMING-REPLICATION).

  • Install Failover Manager on each primary and standby node. During Advanced Server installation, you configured an EnterpriseDB repository on each database host. You can use the EnterpriseDB repository and the `yum install` command to install Failover Manager on each node of the cluster:

*   yum install edb-efm43

During the installation process, the installer creates a user named efm that has privileges to invoke scripts that control the Failover Manager service for clusters owned by enterprisedb or postgres. The example that follows creates a cluster named efm.

Start the configuration process on a primary or standby node. Then, copy the configuration files to other nodes to save time.

  1. Create working configuration files. Copy the provided sample files to create Failover Manager configuration files, and correct the ownership:

*  cd /etc/edb/efm-4.4
*   cp efm.properties.in efm.properties
*   cp efm.nodes.in efm.nodes
*   chown efm:efm efm.properties
*   chown efm:efm efm.nodes

  1. Create an encrypted password needed for the properties file:

*  /usr/edb/efm-4.4/bin/efm encrypt efm

  • Follow the onscreen instructions to produce the encrypted version of your database password.

  1. Update efm.properties. The <cluster_name>.properties file (efm.properties in this example) contains parameters that specify connection properties and behaviors for your Failover Manager cluster. Modifications to property settings are applied when Failover Manager starts.

    • The properties mentioned in this tutorial are the minimal properties required to configure a Failover Manager cluster. If you’re configuring a production system, review the Failover Manager User Guide for detailed information about Failover Manager options.

    • Provide values for the following properties on all cluster nodes:

    • Property | Description | | ———————– | ——————————————————————————————————————————– | | db.user | The name of the database user. | | db.password.encrypted | The encrypted password of the database user. | | db.port | The port monitored by the database. | | db.database | The name of the database. | | db.service.owner | The owner of the data directory (usually postgres or enterprisedb). Required only if the database is running as a service. | | db.service.name | The name of the database service (used to restart the server). Required only if the database is running as a service. | | db.bin | The path to the bin directory (used for calls to pg_ctl). | | db.data.dir | The data directory in which EFM will find or create the recovery.conf file or the standby.signal file. | | user.email | An email address at which to receive email notifications (notification text is also in the agent log file). | | bind.address | The local address of the node and the port to use for Failover Manager. The format is: bind.address=1.2.3.4:7800 | | is.witness | true on a witness node and false if it is a primary or standby. | | ping.server.ip | If you are running on a network without Internet access, set ping.server.ip to an address that is available on your network. | | auto.allow.hosts | On a test cluster, set to true to simplify startup; for production usage, consult the user’s guide. | | stable.nodes.file | On a test cluster, set to true to simplify startup; for production usage, consult the user’s guide. |

  2. Update efm.nodes. The <cluster_name>.nodes file (efm.nodes in this example) is read at startup to tell an agent how to find the rest of the cluster or, in the case of the first node started, can be used to simplify authorization of subsequent nodes. Add the addresses and ports of each node in the cluster to this file. One node acts as the membership coordinator. Include in the list at least the membership coordinator’s address. For example:

1.2.3.4:7800

1.2.3.5:7800

1.2.3.6:7800

  • The Failover Manager agent doesn’t validate the addresses in the efm.nodes file. The agent expects that some of the addresses in the file can’t be reached (for example, that another agent hasn’t been started yet).

  1. Configure the other nodes. Copy the efm.properties and efm.nodes files to /etc/edb/efm-4.4 on the other nodes in your sample cluster. After copying the files, change the file ownership so the files are owned by efm:efm. The efm.properties file can be the same on every node, except for the following properties:

      • Modify the bind.address property to use the node’s local address. - Set is.witness to true if the node is a witness node. If the node is a witness node, the properties relating to a local database installation are ignored.

  2. Start the Failover Manager cluster. On any node, start the Failover Manager agent. The agent is named edb-efm-4.4; you can use your platform-specific service command to control the service. For example, on a CentOS/RHEL 7.x or CentOS/RHEL 8.x host, use the command:

*  systemctl start edb-efm-4.4

  • On a CentOS or RHEL 6.x host, use the command:

*  service edb-efm-4.4 start

  1. After the agent starts, run the following command to see the status of the single-node cluster. The addresses of the other nodes appear in the Allowed node host list.

*  /usr/edb/efm-4.4/bin/efm cluster-status efm

  1. Start the agent on the other nodes. Run the efm cluster-status efm command on any node to see the cluster status.

    • If any agent fails to start, see the startup log for information about what went wrong:

*  cat /var/log/efm-4.4/startup-efm.log

Perform a switchover

If the cluster status output shows that the primary and standby nodes are in sync, you can perform a switchover:

*  /usr/edb/efm-4.4/bin/efm promote efm -switchover

The command promotes a standby and reconfigures the primary database as a new standby in the cluster. To switch back, run the command again.

Access online help

For quick access to online help, use:

*  /usr/edb/efm-4.4/bin/efm --help