Introduction

Using a JS7 - Agent Cluster provides high availability and is a feature that is subject to the JS7 - License.

• Fail-over is an automated operation that occurs when a Subagent is aborted or killed. Fail-over is applied in case of abnormal termination.
• Switch-over is a manual operation performed by users disabling/enabling Subagents.

For command - line references see the JS7 - Agent - Command Line Operation article.

Test Case for the Agent Cluster

In the Article JS7 - How to set up an Agent Cluster we have set up the Agent cluster with multiple subagents.

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Fail-over Operation

Fail-over occurs when an Active Subagent is terminated abnormally. Fail-over means that the task currently being executed by the Subagent is considered to have failed and that the related order is set to a failed state. An Inactive Subagent is no longer considered for execution of jobs by a Director Agent:

• Subagent Clusters configured for round-robin scheduling will execute jobs with the remaining Subagents. 
• Subagent Clusters configured for fixed-priority scheduling will switch execution of jobs to the next Subagent.

Fail-over can be invoked by the following actions:

• The Active Subagent is killed, for example:
  • for Unix with a SIGKILL signal corresponding to the command: kill -9
  • for Windows with the command: taskkill /F
• From the command line the user performs one of the operationsAgent's Instance Start Script can be used like this:
  • agent_<port>.sh | .cmd abort
  • agent_<port>.sh | .cmd kill

Fail-over will not occur when:

• the Active Subagent is stopped normally from the command line:
  • agent_<port>.sh | .cmd stop
• the operating system is shut down and systemd / init.d or a Windows Service are in place to stop the Subagent normally.

Fail-over happens within a short period of time, typically in 2-3s.

How to test fail-over in the Agent Cluster

Round-robin Subagent Cluster

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round_robin_normal_operation round_robin_normal_operation

Scenario for normal Cluster Operation

The In the Article JS7 - How to set up an Agent Cluster we have set up the Agent cluster with multiple subagents article explains how to set up a number of Subagents.

1. Create a workflow from the configuration Configuration view and assigned assign the same Agent Cluster to all the jobs. Once the configuration is completed deploy the workflow.
   
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2. The Agent cluster Cluster is configured as a for round-robin scheduling and executes each next job on with the next Subagent.
3. To test this switch cluster behavior navigate to the Workflows tab view and select the a workflow from the folder tree structure.
   
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4. Expand the workflow and add an order.
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5. Once the workflow completed successfully open the log from the history panel.
   
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6. In the log, you can identify that all jobs use different Subagents as the Agent Cluster is set up for round-robin scheduling. Each next job is executed with the next Subagent.

Scenario for fail-over Cluster Operation

1. Kill one of the Active Subagents from the command line to force fail-over with one of the below commands.
   • An Active Subagent is killed, for example:
     • for Unix with a SIGKILL signal corresponding to the command: kill -9
     • for Windows with the command: taskkill /F
   • From the command line the Agent Instance Start Script can be used like this:
     • agent_<port>.sh | .cmd abort
     • agent_<porr>.sh | .cmd kill

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2. Check the order log to verify that jobs in the workflow are successfully executed with all remaining Subagents.

Fixed-priority Subagent Cluster

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fixed_priority_normal_operation fixed_priority_normal_operation

Scenario for normal Cluster Operation

The scenario is similar to the Scenario for normal Cluster Operation of a round-robin Subagent Cluster with the exception that jobs are assigned a Subagent Cluster that is set up for fixed-priority scheduling.

Fixed-priority means that all jobs will be executed with the first Subagent unless it becomes unavailable and only then jobs will be executed with the next Subagent.

Scenario for fail-over Cluster Operation

1. Kill the Active Subagent from the command line to force fail-over with one of the below commandsKill any of the SubAgent from the windows command line or from the Linux terminal to execute the fail-over test case with the below command.
   • The Active Subagent is killed, for example:
     • for Unix with a SIGKILL signal corresponding to the command: kill -9
     • for Windows with the command: taskkill /F
   • From the command line the user performs one of the operationsAgent Instance Start Script can be used like this:
     • agent_<port>.sh | .cmd abort
     • agent_<porr>.sh | .cmd kill

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2. Check the order log to verify that any jobs in the workflow are successfully executed with the next Subagent.