Virtimo Cluster manager

The use of the cluster manager requires a license. A separate license must be purchased for each INUBIT instance within a cluster.

Usage

With the Virtimo Cluster Manager it is possible to merge several INUBIT instances into a cluster, add or remove new instances at runtime.

In this way, for example, a high availability of an INUBIT system can be achieved or a targeted reaction to high loads can be achieved.

Prerequisites

The following components are necessary for the complete implementation of a clustered system:

INUBIT instances: At least two INUBIT installations, including a license for using the cluster manager
JGroups: INUBIT instances must be able to communicate with each other via JGroups
Load-Balancer: To distribute the incoming requests to the INUBIT instances of the cluster

The cluster manager controls which nodes belong to the cluster and who is the current leader. The load balancer takes care of the distribution of incoming requests to the individual INUBIT instances in the cluster. This separation of responsibilities must be taken into account during configuration.

Architecture

A cluster always consists of a leader node and any number of backup nodes. If INUBIT instances are to work together in a cluster, this must be taken into account when implementing the technical workflows.

Leader node

The leader node takes over all tasks that are to be carried out within the system on a single node, e.g. scheduled workflows.

Backup node

All nodes (leader and backup) take over the tasks that can be technically executed in parallel. An additional workflow is used to check whether the current INUBIT instance is a leader or backup node.

Application status

The cluster manager also runs on every INUBIT instance and checks independently at regular intervals whether the instance is still available. If the INUBIT can no longer be reached, the instance is logged off from the cluster. Logging off in the load balancer is not a task of the cluster manager and must be solved separately.

The following INUBIT REST-API endpoints can be used to check the status:

Configuration

Activation of the cluster manager

The cluster manager can be activated via the file <inubit-installdir>/inubit/server/ibis_root/conf/ibis.xml:

<Properties>
     ...
     <!-- Cluster Manager configuration -->
     <Property name="ActivateClusterManager" type="Boolean">false</Property>
</Properties>

Stop Process Engine
Set property ActivateClusterManager to true
Start Process Engine

Configuration of the cluster manager

The actual configuration details for the cluster manager are controlled via the file <inubit-installdir>/inubit/server/ibis_root/conf/clustermanager/virtimo_cluster_manager.xml. All the settings required for cluster node configuration are made here.

All possible configuration options are documented in the file.
Default JGroups configuration is present in <inubit-installdir>/inubit/server/ibis_root/conf/clustermanager/jgroups.xml. All the settings required for communication between nodes are made here.

The file contains all possible configuration options, which can be accessed through this link JGroups.

Defining the leader node

The priority setting determines which node should be active as the leader in the cluster. Specify the highest integer value for exactly one instance in the configuration. As soon as this instance joins the cluster, it is set as the leader.

If the leader fails, a new leader is selected based on the priority of the other instances. This is the instance with the currently highest priority.

Configure a different priority for each INUIBT instance in the cluster. This is the safest way to control the choice of leader node.

Checking for the leader node

A file is stored in the file system on the instance that is active as the leader. The path to the storage can be adjusted via the configuration. An additional workflow checks for the existence of this file. This can be used to determine at runtime whether the respective INUBIT instance is the leader node or not.

The workflow can be found at: <inubit-installdir>/inubit/server/ibis_root/conf/clustermanager/inubit-cluster-manager-workflow.zip.

Enable custom logging

To redirect the logging output of the cluster manager into a separate file proceed as follows:

Login with a Workbench
Go to Administrator tab and select General Settings
In the tree navigate to Logging > Trace
On the right side panel select Custom server trace and click "…" button
Logger dialog opens
Right click to open the context menu and select Add
Enter the name de.virtimo.inubit.clustermanager, choose Rolling file logger and click OK
If you want to update log file name, select the newly added entry in the table and click "…" button
Select "Output file" and adjust to value to something like $ibis.root.directory$/log/clustermanager.log
Close the "Rolling file logger" dialog with OK
Close the "Logger" dialog with OK
Save the general settings by clicking on the save icon in the global toolbar