Scope

• Fault Tolerance, Resilience and Redundancy provide high-availability of JobScheduler for a number of outage scenarios:
  
  • High Availability requires the system including JobScheduler, database, storage etc. to be available, not just one component. 
  • High Availability is oriented towards specific outage scenarios, not towards any possible failure. 
• Master / Agent Resilience includes a number of measures for operational robustness:
  • Master / Agent Reconciliation allows continued execution of tasks in case of recoverable Network Connection Loss.
  • Master Service Recovery includes supported measures after a Master Service Failure.
  • Database Service Recovery includes the capability to recover in case of Database Connection Loss.
• Master / Agent Redundancy includes a number of architecture decisions:
  • Master Clusters provide redundancy of Master instances in a network.
  • Agent Clusters can be used to compensate the outage of a server that runs an Agent.
• Recovery Strategies provide an overview of means how to restore the scheduling service

Master / Agent Redundancy

Master Cluster

Feature

• JobScheduler Master supports Cluster Operation with redundancy of the involved cluster members.
  • see Passive Cluster
  • see Active Cluster
  • see Master / Agent Cluster
• Clustering is frequently used for high-availability and in some cases for improved performance.

Agent Cluster

Feature

• The JobScheduler allows multiple Agents to be specified for a single Process Class.
  • The JobScheduler Master contacts Agents in round-robin mode:
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    • the first Agent that is configured to execute jobs for the process class will be contacted.
    • if the first Agent is not available then the next Agent listed in the process class configuration will be contacted
    • this procedure will be repeated until an Agent is found that can execute the job.
  • Use cases for this scenario include
    • all Agents running on different server nodes: the switch to the next available Agent implements a fail-over to the next server node.
    • a number of Agents running on the same server node: the switch to the next available Agent implements redundancy  of Agents within a single server node.
• Feature Availability
  • FEATURE AVAILABILITY STARTING FROM RELEASE 1.9

Delimitation

• This feature is not intended for load sharing as the JobScheduler will always use the first available Agent.
• This feature is not intended for scalability as it does not allow the execution of jobs in parallel on a number of Agents (clustering).

Change Management References