simpleq

A super simple Redis-backed queue.

Operation

Install:

npm install simpleq

Creation:

varredis=require('redis'),cli=redis.createClient();varsimpleq=require('simpleq'),q=newsimpleq.Q(cli,'my-simpleq');

Operations:

• q.push(el, cb) Returns number of elements in queue.
• q.pop(cb) and q.bpop(cb) (blocking) Returns element popped or null
• q.pull(el, cb) Pull out a specific el (the highest/oldest el in the queue to be specific if elements are repeated) from the queue. Returns number of elements removed (0 or 1).
• q1.pullpipe(q2, el, cb) Pull and push into another queue atomicly. Returns elements in second queue. (Note, that if el does not exist in q1, it will still be put into q2)
  • q1.spullpipe(q2, el, cb) is a safe version which will not insert el into q2 unless it has been successfully pulled out of q1. This is done atomically using a lua script.
• q1.poppipe(q2, cb) and q1.bpoppipe(q2, cb) (blocking): Pop and push to another queue; returns popped element (also atomic).
• q.clear(cb) Clear out the queue
• q.list(cb) List all elements in the queue

Listeners:

simpleq's can start listeners that run bpoppipe or bpop continuously and make callbacks when they occur. These two functions are .poplisten and .poppipelisten. The both accept two options:

• max_out (default: 0 ~ infinity) Maximum number of callbacks allowed to be out at one time.

The callbacks on a message from a listener pass a done function that must be called when processing is complete. If not in the same closure, listener.done() and listener.emit('done'); will suffice.

Note: Calling listen will clone the redis connection, allowing .push to still work because another connection is being blocked. Calling a listen function more than once will result in a thrown error, as this is not prudent.

Examples below:

varlistener=q.poplisten({redisClone: newRedis(),max_out: 10});// orvarlistener=q.poppipelistener(otherq,{redisClone: newRedis(),max_out: 10});// thenlistener.on('ready',function(){// listener is ready to go and running}).on('message',function(msg,done){// do stuffdone();// idempotent. you can call it more than once.}).on('error',function(err){console.error(err);});// eventuallylistener.once('end',functionwhenItIsReallyReadyToEnd(){...})// after all jobs have finished.end();// idempotent if you've already ended the listener

Tests

npm install -g nodeunit
nodeunit test

License

See LICENSE file.