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    job-pipe

    1.0.3 • Public • Published

    job-pipe

    by Vytenis Urbonavičius

    Job Pipe provides a simple way to limit parallel executions of one or more JavaScript functions. Parallel execution limit is configurable.

    If limit is exceeded, further jobs are queued until a configured maximum queue length is reached. When that limit is exceeded, oldest waiting job is dismissed and new job is added to the queue.


    Typical Usage

    import {createPipe} from 'job-pipe'
    
    const pipe = createPipe()
    
    const foo1 = async () => {
      // Do something asynchronous
    }
    
    const foo2 = () =>
      new Promise(resolve => {
        // Do something asynchronous
        resolve(result)
      })
    
    const pipedFoo1 = pipe(foo1)
    const pipedFoo2 = pipe(foo2)
    
    const promise1 = pipedFoo1() // Will be executed at once
    const promise2 = pipedFoo2() // Will wait for promise1 to resolve
    
    // Below call will reject promise2 with JobPipeQueueExceeded
    // and then wait for promise1 before execution
    const promise3 = pipedFoo1()

    Piped functions accept same arguments and return same results as original ones (unless they are rejected due to configured pipe limitations as documented further in this readme).


    Custom Pipe

    Pipe can be customized by providing optional pipe properties to createPipe as object with keys:

    Key Default value Meaning
    throughput 1 Maximum amount of parallel executions
    maxQueueSize 1 Maximum amount of waiting jobs. If additional job is triggered when queue is full, oldest waiting job will be rejected with JobPipeQueueExceeded exception and new job will be added to the end of queue. For unlimited queue use {maxQueueSize: Infinity}.

    Example:

    const pipe = createPipe({
      throughput: 2,
      maxQueueSize: 2,
    })

    Additional API

    When pipe is created, there are additional methods attached to the response:

    const pipe = createPipe()
    
    // Provides amount of jobs which are currently being executed in parallel
    pipe.getFlowWidth()
    
    // Provides amount of jobs which are waiting for execution
    pipe.getQueueLength()
    
    // Rejects promises of all jobs with JobPipeAborted exception
    // Clears the pipe and removes all jobs from queue
    pipe.abort()

    Thrown Exceptions

    Exception Class Meaning
    JobPipeError Any exception which is handled by Job Pipe is a child of this class. JobPipeError extends default JavaScript Error.
    JobPipeQueueExceeded Job is rejected with this exception when it has been cancelled because maximum queue size was exceeded.
    JobPipeAborted Job is rejected with this exception when whole Job Pipe is manually aborted.

    Example of how aborted jobs can be ignored:

    const pipe = createPipe()
    
    const pipedFn = pipe(someFunction)
    
    try {
      await pipedFn()
    } catch (e) {
      if (!(e instanceof JobPipeAborted)) {
        throw e
      }
    }

    Funky Visualization

    Happy Hacking!

    Install

    npm i job-pipe

    DownloadsWeekly Downloads

    1

    Version

    1.0.3

    License

    MIT

    Unpacked Size

    73.5 kB

    Total Files

    10

    Last publish

    Collaborators

    • white-turbine