@lokalise/background-jobs-common

Common background jobs library

This library provides a basic abstraction over BullMQ-powered background jobs. There are two types available:

• AbstractBackgroundJobProcessor: a base class for running jobs, it provides a NewRelic and logger integration plus basic API for enqueuing jobs.
• AbstractStepBasedJobProcessor: a base class for step-based jobs. Logic has to be defined in classes that implement a JobStep interface and have a job data which extends StepBasedJobData type

Getting Started

Install all dependencies:

npm install

Run all tests:

npm run test

Usage

See test implementations in ./test/processors folder. Extend either AbstractBackgroundJobProcessor or AbstractStepBasedJobProcessor and implement required methods.

Common jobs

For that type of jobs, you will need to extend AbstractBackgroundJobProcessor and implement a processInternal method. It will be called when a job is dequeued. Processing logic is automatically wrapped into NewRelic and basic logger calls, so you only need to add your domain logic.

Both queue and worker is automatically started when you instantiate the processor. There is a default configuration which you can override by passing queueConfig.queueOptions and workerOptions params to the constructor.

Use dispose() to correctly stop processing any new messages and wait for the current ones to finish.

Step-based jobs

To create a step-based job, extend the AbstractStepBasedJobProcessor. This is a more complex type of job processor (based on the previous one) - it can only run via specific classes which implement the actual logic, and it has some restrictions on the job data generic type.

You will need to implement the following methods:

getStepTransitions(): Record<PropertyKey, JobStep<JobData> | null>

Define a map of your job steps here: keys correspond to the current job state (JobData.execution.state) and values are instances of a JobStep interface or null values (they finish the job execution). Each step has to implement a run method which returns a new execution object - it will replace the existing one after the step is finished.

Example implementation:

protected getStepTransitions(): Record <string | number, JobStep<TestJobData> | null> {
  return {
    initial: new StepFirst(),
    'other-state': new StepSecond(),
    completed: null,
  }
}

In the example above (depending on the getDefaultExecutionState implementation), the job will start in the initial state and proceed as follows:

• StepFirst will be executed
• (if execution.state has changed to other-state) StepSecond will be executed
• (if execution.state has changed to completed) the job will be finished

getDefaultExecutionState(): JobData['execution']

Define the default job execution state here. It will be used when a job is scheduled.

onError(error: Error | unknown, job: Job<JobData>): Promise<void>

Define the error handler here. It will be called when any of the steps throws an exception.