Job service
The Job service schedules and executes tasks in a cloud environment. Independent services implement these tasks, which can be initiated through any of the supported interaction modes, including HTTP calls or Knative Events delivery.
In OpenShift Serverless Logic, the Job service is responsible for controlling the execution of the time-triggered actions. Therefore, all the time-based states that you can use in a workflow, are handled by the interaction between the workflow and the Job service.
For example, every time the workflow execution reaches a state with a configured timeout, a corresponding job is created in the Job service, and when the timeout is met, an HTTP callback is executed to notify the workflow.
The main goal of the Job service is to manage active jobs, such as scheduled jobs that need to be executed. When a job reaches its final state, the Job service removes it. To retain jobs information in a permanent repository, the Job service produces status change events that can be recorded by an external service, such as the Data Index service.
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You do not need to manually install or configure the Job service if you are using the OpenShift Serverless Operator to deploy workflows. The Operator handles these tasks automatically and manages all necessary configurations for each workflow to connect with it. |
Job service leader election process
The Job service operates as a singleton service, meaning only one active instance can schedule and execute jobs.
To prevent conflicts when the service is deployed in the cloud, where multiple instances might be running, the Job service supports a leader election process. Only the instance that is elected as the leader manages external communication to receive and schedule jobs.
Non-leader instances remain inactive in a standby state but continue attempting to become the leader through the election process. When a new instance starts, it does not immediately assume leadership. Instead, it enters the leader election process to determine if it can take over the leader role.
If the current leader becomes unresponsive or if it is shut down, another running instance takes over as the leader.
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This leader election mechanism uses the underlying persistence backend, which is currently supported only in the PostgreSQL implementation. |