e277501ca3
Once a job has been enqueued, there is no way to query its dependencies. This makes dequeue more symmetric to enqueue by returning the dependencies that were passed to enqueue, allowing the caller to query the dependencies and their results. Signed-off-by: Tom Gundersen <teg@jklm.no>
66 lines
2.4 KiB
Go
66 lines
2.4 KiB
Go
// Package jobqueue provides a generic interface to a simple job queue.
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//
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// Jobs are pushed to the queue with Enqueue(). Workers call Dequeue() to
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// receive a job and FinishJob() to report one as finished.
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//
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// Each job has a type and arguments corresponding to this type. These are
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// opaque to the job queue, but it mandates that the arguments must be
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// serializable to JSON. Similarly, a job's result has opaque result arguments
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// that are determined by its type.
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//
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// A job can have dependencies. It is not run until all its dependencies have
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// finished.
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package jobqueue
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import (
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"context"
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"encoding/json"
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"errors"
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"time"
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"github.com/google/uuid"
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)
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// JobQueue is an interface to a simple job queue. It is safe for concurrent use.
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type JobQueue interface {
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// Enqueues a job.
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//
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// `args` must be JSON-serializable and fit the given `jobType`, i.e., a worker
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// that is running that job must know the format of `args`.
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//
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// All dependencies must already exist, but the job isn't run until all of them
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// have finished.
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//
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// Returns the id of the new job, or an error.
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Enqueue(jobType string, args interface{}, dependencies []uuid.UUID) (uuid.UUID, error)
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// Dequeues a job, blocking until one is available.
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//
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// Waits until a job with a type of any of `jobTypes` is available, or `ctx` is
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// canceled.
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//
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// Returns the job's id, dependencies, type, and arguments, or an error. Arguments
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// can be unmarshaled to the type given in Enqueue().
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Dequeue(ctx context.Context, jobTypes []string) (uuid.UUID, []uuid.UUID, string, json.RawMessage, error)
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// Mark the job with `id` as finished. `result` must fit the associated
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// job type and must be serializable to JSON.
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FinishJob(id uuid.UUID, result interface{}) error
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// Cancel a job. Does nothing if the job has already finished.
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CancelJob(id uuid.UUID) error
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// Returns the current status of the job, in the form of three times:
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// queued, started, and finished. `started` and `finished` might be the
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// zero time (check with t.IsZero()), when the job is not running or
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// finished, respectively.
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//
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// If the job is finished, its result will be returned in `result`.
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JobStatus(id uuid.UUID, result interface{}) (queued, started, finished time.Time, canceled bool, err error)
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}
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var (
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ErrNotExist = errors.New("job does not exist")
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ErrNotRunning = errors.New("job is not running")
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ErrCanceled = errors.New("job ws canceled")
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)
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