Setting up clusters of servers

To configure a cluster of servers, set up a shared database and file system for the servers to use.

Before you begin

  • Each server in the cluster must run the same version of Deploy.

About this task

To set up servers in a clustered configuration, you install servers on separate systems and connect the servers to the same database and network storage. Several log and configuration files are stored in the shared network storage, but each server also independently maintains some configuration information, such as database and connection information. The database stores other configuration information and runtime data, as well as other information. Because the servers share the database, all servers run on the same interval.
Note: To create a second server in an high-availability setup use the Deploy installer. An install which copies server install files to create a second server is not supported.

Then, you configure a load balancer to distribute the traffic between the servers. Instead of accessing the servers directly, users access the load balancer URL. To the users, that URL appears to host a single instance of the server with high capacity; users are unaware of the multiple servers.

Note: Servers, agents, and agent relays communicate in several ways: via HTTP/HTTPS on the default ports 8080 and 8443, and via WebSocket connects on the default port 7919. To set up the cluster, you must configure the load balancer to distribute the HTTP/HTTPS traffic. In general, load balancers work well with HTTP/HTTPS traffic because this traffic is stateless and works on a request and response cycle.

Procedure

  1. Set up a shared database for the servers to use.
    See Installing the server database.
  2. Set up network storage for the server configuration files.
    Because each cluster server must access the same configuration files, each server must have access to this network storage.
  3. Configure online and offline backups for the servers.
    See Backing up the server.
  4. Install a load balancer to send requests to the servers.
    The load balancer must be able to forward requests to the HTTP and HTTPS ports for the servers. For more information, see the documentation for your load balancer.
    Important: You must configure the load balancer for session persistence, also known as session affinity.
  5. If you have one or more servers already installed, populate the network storage with configuration files for the servers:
    1. Stop one of the existing servers.
    2. On the server, mount the network storage.
    3. From the server installation directory, move the following files and folders to the network storage and update the existing server to access those files and folders.

      Which folders you move depends on how the files are structured on the server and which version the server is running on:

      In this case, follow these steps:
      1. Move the application data folder to the network storage.
      2. On the server, in the installed.properties file, update the server.appdata.dir property to the new location of the application data folder.
      If the server was upgraded from a version prior to 6.1.1.5 to version 6.1.1.5 or later, the server does not have an application data folder. In this case, you must move the folders into an application data folder on the network storage by running these steps:
      1. On the network storage, create a folder to be the application data folder, such as /media/share/appdata.
      2. Copy the following folders to the application data folder:
        • install_folder/var/plugins
        • install_folder/var/repository
        • install_folder/var/sa
        • install_folder/logs
        • install_folder/conf/server/notification-templates
        • install_folder/conf/encryption.keystore
        • install_folder/conf/server.keystore
        • install_folder/conf/collectors
        • install_folder/patches
        • install_folder/conf/server/log4j.properties
        For install_folder, use the installation directory for the server.
      3. Copy (not move) the <server install>/conf/installed.version file to the newly created <appdata>/conf directory.
      4. Verify that the application data folder has the correct folder layout. For example, if you use the /media/share/appdata folder for the application data folder, make sure that you have the following folders and files:
        • /media/share/appdata/var/plugins
        • /media/share/appdata/var/repository
        • /media/share/appdata/var/sa
        • /media/share/appdata/logs
        • /media/share/appdata/conf/server/notification-templates
        • /media/share/appdata/conf/encryption.keystore
        • /media/share/appdata/conf/server.keystore
        • /media/share/appdata/conf/collectors
        • /media/share/appdata/patches
        • /media/share/appdata/conf/server/log4j.properties
        Some of these files and folders might not exist yet.
      5. On the server, in the installed.properties file, set the server.appdata.dir property to the new location of the application data folder.
    4. Delete the original copies of the files and folders that you moved to network storage. (In other words, delete the files on the local server and keep the files on the network storage.)
  6. If you terminate SSL at the server level, set the servers to use the same security certificate.
    For example, you can copy the certificate in the /opt/tomcat/conf/tomcat.keystore file to the other servers. Edit the tomcat.key.alias property in installed.properties file to specify the alias in the keystore that contains the certificate to use.
    tomcat.key.alias=alias_of_your_certificate_in_tomcat_keystore
  7. Optional: Configure the license server for high availability.
    For information, see the Common Licensing documentation. Also, see High availability options for Rational License Key Server.

Results

After you configure the load balancer to distribute connections to the systems, users can connect to a single URL and use the entire cluster. The servers also ensure that the correct number of licenses are used, even if a user accesses multiple servers.

Several server processes behave differently than with individual servers. See High-availability server processes.

What to do next