mongo-dequeue

= Mongo::Dequeue

A de-duplicating priority queue that uses mongodb as the storage engine.

Heavily inspired by Mongo::Queue https://github.com/skiz/mongo_queue

== Features

• Atomic Locking (provided by Mongo)
• Thread Safe
• Priority Support
• Fully Tested
• Simple API

== Examples

=== Setting up a queue Mongo::Dequeue requires a Mongo::Collection, and allows you to configure the default read timeout of items in your queue. Items popped from the queue must be confirmed complete, or they will be reissued after the timeout specified.

mc = Mongo::Connection.new
collection = mc.db("whateverdb").collection("my_queue")

options   = {
  :timeout    => 60
}

queue = Mongo::Dequeue.new(collection, options)

=== Pushing Items Items have a body, passed as the first argument to push(). A body can be a string, number, hash, or array. These values are preserved in the Mongo collection used to store the queue, allowing you to inspect the queue and see these values. The optional options argument is a hash of values. you can set a custom duplicate_key that will be used to de-duplicate queue items. There are no keys or reserved values in the body of an item. Pass in anything you like.

options = {
    :duplicate_key => 'match'
}

body = "foo"
body = 5
body = {
    :stuff => "here"
}
body = ["a", "b", "c"]

queue.push(body,options)

=== Batch Pushing When you need to push more then a few items, the delay of network requests can start to add up. In these cases, you can add more then a single item with a single call, like so:

queue.batchpush("foo")
queue.batchpush("bar")

To perform the actual push, call the batchprocess method:

queue.batchprocess()

=== Popping Items Pop items with the pop() method. Specifying a timeout (in seconds) will override the default timeout set in the queue options. After the timeout, the popped item will be available in another pop() call.

item = queue.pop(:timeout => 1)

The pop call will return a hash, with an :id and a :body. After the queue item is done, be sure to call the complete() method, with the id of the message.

queue.complete(item[:id])

Note that completed items are not removed from the database immediately, allowing inspection of completion times, duplication numbers, etc. Calling the cleanup() method removes completed items.

queue.cleanup()

=== Queue Status You can call the +stats+ method to take a quick peek at your queue. Locked items are items that have been popped, but not confirmed.

queue.stats

=> {:available => 3, :locked => 2, :complete => 5, :total => 10}

=== Mongo::Queue Comparison

• Items are not deleted immediately after completion.
• Item locks auto-expire
• Items are de-duplicated
• No reserved words in item body

=== TODO

• Adjust auto generated duplication_key to be more accurate.
• Full examples