River is a robust high-performance job processing system for Go and Postgres.
See homepage, docs, and godoc, as well as the River UI and its live demo.
Being built for Postgres, River encourages the use of the same database for application data and job queue. By enqueueing jobs transactionally along with other database changes, whole classes of distributed systems problems are avoided. Jobs are guaranteed to be enqueued if their transaction commits, are removed if their transaction rolls back, and aren't visible for work until commit. See transactional enqueueing for more background on this philosophy.
Jobs are defined in struct pairs, with an implementation of JobArgs and one
of Worker.
Job args contain json annotations and define how jobs are serialized to and
from the database, along with a "kind", a stable string that uniquely identifies
the job.
type SortArgs struct {
// Strings is a slice of strings to sort.
Strings []string `json:"strings"`
}
func (SortArgs) Kind() string { return "sort" }Workers expose a Work function that dictates how jobs run.
type SortWorker struct {
// An embedded WorkerDefaults sets up default methods to fulfill the rest of
// the Worker interface:
river.WorkerDefaults[SortArgs]
}
func (w *SortWorker) Work(ctx context.Context, job *river.Job[SortArgs]) error {
sort.Strings(job.Args.Strings)
fmt.Printf("Sorted strings: %+v\n", job.Args.Strings)
return nil
}Jobs are uniquely identified by their "kind" string. Workers are registered on start up so that River knows how to assign jobs to workers:
workers := river.NewWorkers()
// AddWorker panics if the worker is already registered or invalid:
river.AddWorker(workers, &SortWorker{})A River Client provides an interface for job insertion and manages job
processing and maintenance services. A client's created with a database pool,
driver, and config struct containing a Workers bundle and other settings.
Here's a Client working one queue ("default") with up to 100 worker
goroutines at a time:
riverClient, err := river.NewClient(riverpgxv5.New(dbPool), &river.Config{
Queues: map[string]river.QueueConfig{
river.QueueDefault: {MaxWorkers: 100},
},
Workers: workers,
})
if err != nil {
panic(err)
}
// Run the client inline. All executed jobs will inherit from ctx:
if err := riverClient.Start(ctx); err != nil {
panic(err)
}Workers can also be omitted, but it's better to include it so River can check
that inserted job kinds have a worker that can run them.
The client should also be stopped on program shutdown. There's a number of ways
to go about this (see graceful shutdown), but the shortest is to cancel the
context send to Start when the program's ready to stop. For example, to stop
on SIGINT/SIGTERM:
riverClient, err := river.NewClient(riverpgxv5.New(dbPool), &river.Config{
SoftStopTimeout: 10 * time.Second,
...
})
if err != nil {
panic(err)
}
signalCtx, stop := signal.NotifyContext(ctx, syscall.SIGINT, syscall.SIGTERM)
defer stop()
// Stop fetching new work and wait for active jobs to finish. Cancel jobs after
// SoftStopTimeout elapses.
if err := riverClient.Start(signalCtx); err != nil {
panic(err)
}
<-riverClient.Stopped()Alternatively, use an explicit call to Stop:
if err := riverClient.Stop(ctx); err != nil {
panic(err)
}Insert-only clients will insert jobs, but not work them, and don't need to be started or stopped.
Client.InsertTx is used in conjunction with an instance of job args to
insert a job to work on a transaction:
_, err = riverClient.InsertTx(ctx, tx, SortArgs{
Strings: []string{
"whale", "tiger", "bear",
},
}, nil)
if err != nil {
panic(err)
}See the InsertAndWork example for complete code.
River supports inserting jobs in some non-Go languages which are then worked by Go implementations. This may be desirable in performance sensitive cases so that jobs can take advantage of Go's fast runtime.
See developing River.
River was in large part inspired by our experiences with other background job libraries over the years, most notably:
Thank you for driving the software ecosystem forward.