gocron: A Golang Job Scheduling Package

gocron is a job scheduling package which lets you run Go functions at pre-determined intervals.

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Check out gocron-ui — a lightweight web dashboard to monitor, trigger, and manage your gocron jobs in real time.

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Quick Start

go get github.com/go-co-op/gocron/v2

package main

import (
    "fmt"
    "time"

    "github.com/go-co-op/gocron/v2"
)

func main() {
    // create a scheduler
    s, err := gocron.NewScheduler()
    if err != nil {
        // handle error
    }

    // add a job to the scheduler
    j, err := s.NewJob(
        gocron.DurationJob(
            10*time.Second,
        ),
        gocron.NewTask(
            func(a string, b int) {
                // do things
            },
            "hello",
            1,
        ),
    )
    if err != nil {
        // handle error
    }
    // each job has a unique id
    fmt.Println(j.ID())

    // start the scheduler
    s.Start()

    // block until you are ready to shut down
    select {
    case <-time.After(time.Minute):
    }

    // when you're done, shut it down
    err = s.Shutdown()
    // or for context-aware teardown: 
    // err = s.ShutdownWithContext(ctx)
    if err != nil {
        // handle error
    }
}

Examples

• Go doc examples
• Examples directory

Articles & Blog Posts

Community articles and tutorials about using gocron:

• Building a dynamic, highly available scheduler in Go - A deep dive into building a highly available scheduler using gocron, MongoDB change streams, and leader election patterns for the FACEIT Watch platform.

Concepts

• Job: The job encapsulates a "task", which is made up of a go function and any function parameters. The Job then provides the scheduler with the time the job should next be scheduled to run.
• Scheduler: The scheduler keeps track of all the jobs and sends each job to the executor when it is ready to be run.
• Executor: The executor calls the job's task and manages the complexities of different job execution timing requirements (e.g. singletons that shouldn't overrun each other, limiting the max number of jobs running)

Features

Job types

Jobs can be run at various intervals. - Duration: Jobs can be run at a fixed time.Duration. - Random duration: Jobs can be run at a random time.Duration between a min and max. - Cron: Jobs can be run using a crontab. - Daily: Jobs can be run every x days at specific times. - Weekly: Jobs can be run every x weeks on specific days of the week and at specific times. - Monthly: Jobs can be run every x months on specific days of the month and at specific times. - One time: Jobs can be run at specific time(s) (either once or many times).

Interval Timing

Jobs can be scheduled with different interval timing modes. - Interval from scheduled time (default): By default, jobs calculate their next run time from when they were scheduled to start, resulting in fixed intervals regardless of execution time. Good for cron-like scheduling at predictable times. - Interval from completion time: Jobs can calculate their next run time from when they complete, ensuring consistent rest periods between executions. Ideal for rate-limited APIs, resource-intensive jobs, and scenarios where execution time varies.

Concurrency Limits

Jobs can be limited individually or across the entire scheduler. - Per job limiting with singleton mode: Jobs can be limited to a single concurrent execution that either reschedules (skips overlapping executions) or queues (waits for the previous execution to finish). - Per scheduler limiting with limit mode: Jobs can be limited to a certain number of concurrent executions across the entire scheduler using either reschedule (skip when the limit is met) or queue (jobs are added to a queue to wait for the limit to be available). - Note: A scheduler limit and a job limit can both be enabled.

Distributed instances of gocron

Multiple instances of gocron can be run. - Elector: An elector can be used to elect a single instance of gocron to run as the primary with the other instances checking to see if a new leader needs to be elected. - Implementations: go-co-op electors (don't see what you need? request on slack to get a repo created to contribute it!) - Locker: A locker can be used to lock each run of a job to a single instance of gocron. Locker can be at job or scheduler, if it is defined both at job and scheduler then locker of job will take precedence. - See Notes in the doc for Locker for details and limitations of the locker design. - Implementations: go-co-op lockers (don't see what you need? request on slack to get a repo created to contribute it!)

Events

Job events can trigger actions. - Listeners: Can be added to a job, with event listeners, or all jobs across the scheduler to listen for job events and trigger actions.

Options

Many job and scheduler options are available. - Job options: Job options can be set when creating a job using NewJob. - Global job options: Global job options can be set when creating a scheduler using NewScheduler and the WithGlobalJobOptions option. - Scheduler options: Scheduler options can be set when creating a scheduler using NewScheduler.

Logging

Logs can be enabled. - Logger: The Logger interface can be implemented with your desired logging library. The provided NewLogger uses the standard library's log package.

Metrics

Metrics may be collected from the execution of each job and scheduler lifecycle events. - Monitor: A monitor can be used to collect metrics for each job from a scheduler. - Implementations: There are currently no open source implementations of the Monitor interface available. We'd love for you to be the first to contribute one! Check out the Monitor interface documentation to get started, or reach out on Slack if you'd like to discuss your implementation. - MonitorStatus: Extends Monitor with status and error tracking for each job. - Implementations: There are currently no open source implementations of the MonitorStatus interface available. We'd love for you to be the first to contribute one! Check out the MonitorStatus interface documentation to get started, or reach out on Slack if you'd like to discuss your implementation. - SchedulerMonitor: A scheduler monitor provides comprehensive observability into scheduler and job lifecycle events.

Available Metrics: - Scheduler Lifecycle: SchedulerStarted, SchedulerStopped, SchedulerShutdown - Job Management: JobRegistered, JobUnregistered - track jobs added/removed from scheduler - Job Execution: JobStarted, JobRunning, JobCompleted, JobFailed - monitor job execution flow - Performance: JobExecutionTime, JobSchedulingDelay - measure job duration and scheduling lag - Concurrency: ConcurrencyLimitReached - detect when singleton or limit mode constraints are hit

Derived Metrics (calculable from events): - Error rate: JobFailed / (JobCompleted + JobFailed) - Average execution time: from JobExecutionTime events - Active jobs: JobRegistered - JobUnregistered - Current queue depth: JobStarted - (JobCompleted + JobFailed)

Example - Prometheus Integration: ```go type PrometheusMonitor struct { jobsCompleted prometheus.Counter jobsFailed prometheus.Counter executionTime prometheus.Histogram schedulingDelay prometheus.Histogram }

func (p *PrometheusMonitor) JobExecutionTime(job gocron.Job, duration time.Duration) { p.executionTime.Observe(duration.Seconds()) }

func (p *PrometheusMonitor) JobSchedulingDelay(job gocron.Job, scheduled, actual time.Time) { if delay := actual.Sub(scheduled); delay > 0 { p.schedulingDelay.Observe(delay.Seconds()) } }

// Initialize scheduler with monitor s, _ := gocron.NewScheduler(gocron.WithSchedulerMonitor(monitor)) ```

Use Cases: Prometheus metrics, custom dashboards, alerting systems, performance monitoring

• Implementations: There are currently no open source implementations of the SchedulerMonitor interface available. We'd love for you to be the first to contribute one! Check out the SchedulerMonitor interface documentation to get started, or reach out on Slack if you'd like to discuss your implementation.

Testing

The gocron library is set up to enable testing. - Mocks are provided in the mock package using gomock. - Time can be mocked by passing in a FakeClock to WithClock - see the example on WithClock.

Supporters

We appreciate the support for free and open source software!

This project is supported by:

JetBrains

Sentry

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