Introduction

Qrono is a time-ordered queue server.

⚠️ Qrono is a hobby project. It is not production ready.

Values in a Qrono queue are ordered by their deadline and can only be dequeued once their deadline has passed. A deadline can be specified when enqueuing or requeuing a value and defaults to the current time. Values with equal deadlines are processed in FIFO order.

Qrono provides multiple interfaces. In addition to standard HTTP and gRPC interfaces, Qrono provides a Redis-compatible RESP interface allowing redis-cli and many existing Redis client libraries to be used.

Queue operations

Enqueue

ENQUEUE queue value [DEADLINE milliseconds-timestamp]
  (integer) id
  (integer) deadline

Add a value to the queue with the given deadline which defaults to now. After being enqueued the value is considered pending.

Dequeue

DEQUEUE queue
  (integer) id
  (integer) deadline
  (integer) enqueue-time
  (integer) requeue-time
  (integer) dequeue-count
  (bulk) value

Dequeue the next pending value from the queue if available. Returns null if the queue is empty, or the deadline of the next value in the queue lies in the future. On success, the next pending value in the queue is moved into the dequeued state.

Requeue

REQUEUE queue id [DEADLINE milliseconds-timestamp]
  OK

Requeue a dequeued value by id, returning it to pending status. If not specified, deadline will default to now.

Release

RELEASE queue id
  OK

Release a dequeued value by id.

Peek

PEEK queue
  (integer) id
  (integer) deadline
  (integer) enqueue-time
  (integer) requeue-time
  (integer) dequeue-count
  (bulk) value

Returns, but does not dequeue the next pending value from the queue. Returns null if the queue is empty.

Stat

STAT queue
  (integer) pending-count
  (integer) dequeued-count

Returns statistics for the queue including the number of pending and dequeued values. The pending count includes dequeued values.