Package tasks is an easy to use in-process scheduler for recurring tasks in Go. Tasks is focused on high frequency tasks that run quick, and often. The goal of Tasks is to support concurrent running tasks at scale without scheduler induced jitter.

Tasks is focused on accuracy of task execution. To do this each task is called within it's own goroutine. This ensures that long execution of a single invocation does not throw the schedule as a whole off track.

For simplicity this task scheduler uses the time.Duration type to specify intervals. This allows for a simple interface and flexible control over when tasks are executed.

• Concurrent Execution: Tasks are executed in their own goroutines, ensuring accurate scheduling even when individual tasks take longer to complete.
• Optimized Goroutine Scheduling: Tasks leverages Go's time.AfterFunc() function to reduce sleeping goroutines and optimize CPU scheduling.
• Flexible Task Intervals: Tasks uses the time.Duration type to specify intervals, offering a simple interface and flexible control over task execution timing.
• Delayed Task Start: Schedule tasks to start at a later time by specifying a start time, allowing for greater control over task execution.
• One-Time Tasks: Schedule tasks to run only once by setting the RunOnce flag, ideal for single-use tasks or one-time actions.
• Single-Instance Tasks: Prevent overlapping runs by setting RunSingleInstance, which skips a run if the previous invocation is still executing.
• Task Context Support: Pass user-defined context and task metadata into callbacks with FuncWithTaskContext, ErrFuncWithTaskContext, and TaskContext.ID().
• Custom Error Handling: Define a custom error handling function to handle errors returned by tasks, enabling tailored error handling logic.
• Custom Task IDs: Provide your own task IDs with AddWithID when you need deterministic identifiers.

Here are some examples to help you get started with Tasks:

// Start the Scheduler
scheduler := tasks.New()
defer scheduler.Stop()

// Add a task
id, err := scheduler.Add(&tasks.Task{
  Interval: 30 * time.Second,
  TaskFunc: func() error {
    // Put your logic here
    return nil
  },
})
if err != nil {
  // Do Stuff
}

Sometimes schedules need to started at a later time. This package provides the ability to start a task only after a certain time. The below example shows this in practice.

// Add a recurring task for every 30 days, starting 30 days from now
id, err := scheduler.Add(&tasks.Task{
  Interval: 30 * (24 * time.Hour),
  StartAfter: time.Now().Add(30 * (24 * time.Hour)),
  TaskFunc: func() error {
    // Put your logic here
    return nil
  },
})
if err != nil {
  // Do Stuff
}

It is also common for applications to run a task only once. The below example shows scheduling a task to run only once after waiting for 60 seconds.

// Add a one time only task for 60 seconds from now
id, err := scheduler.Add(&tasks.Task{
  Interval: 60 * time.Second,
  RunOnce:  true,
  TaskFunc: func() error {
    // Put your logic here
    return nil
  },
})
if err != nil {
  // Do Stuff
}

One powerful feature of Tasks is that it allows users to specify custom error handling. This is done by allowing users to define a function that is called when a task returns an error. The below example shows scheduling a task that logs when an error occurs.

// Add a task with custom error handling
id, err := scheduler.Add(&tasks.Task{
  Interval: 30 * time.Second,
  TaskFunc: func() error {
    // Put your logic here
    return nil
  },
  ErrFunc: func(e error) {
    log.Printf("An error occurred when executing task %s - %s", id, e)
  },
})
if err != nil {
  // Do Stuff
}

Use RunSingleInstance when a task might take longer than its interval and overlapping executions should be skipped.

id, err := scheduler.Add(&tasks.Task{
  Interval:          30 * time.Second,
  RunSingleInstance: true,
  TaskFunc: func() error {
    // Put your logic here
    return nil
  },
})
if err != nil {
  // Do Stuff
}

Use the context-aware callbacks when you want to pass a user-defined context into task execution and error handling.

ctx := context.Background()

id, err := scheduler.Add(&tasks.Task{
  Interval:    30 * time.Second,
  TaskContext: tasks.TaskContext{Context: ctx},
  FuncWithTaskContext: func(taskCtx tasks.TaskContext) error {
    log.Printf("running task %s", taskCtx.ID())
    return nil
  },
  ErrFuncWithTaskContext: func(taskCtx tasks.TaskContext, err error) {
    log.Printf("task %s failed: %v", taskCtx.ID(), err)
  },
})
if err != nil {
  // Do Stuff
}

Use AddWithID when you want to provide your own stable identifier for a task.

err := scheduler.AddWithID("nightly-report", &tasks.Task{
  Interval: time.Hour,
  TaskFunc: func() error {
    // Put your logic here
    return nil
  },
})
if err != nil {
  // Do Stuff
}

For more details on usage, see the GoDoc.

Contributions are welcome! Please see CONTRIBUTING.md for more details.

Common local workflows are available through the repository Makefile:

• make build
• make tests
• make benchmarks
• make coverage
• make lint
• make format