Redis based queues and workers.
Ost makes it easy to enqueue object ids and process them with workers.
Say you want to process video uploads. In your application you will have something like this:
Ost[:videos_to_process].push(@video.id)
Then, you will have a worker that will look like this:
require "ost"
Ost[:videos_to_process].each do |id|
# Do something with it!
end
Ost connects to Redis automatically with the default options (localhost:6379, database 0).
You can customize the connection by calling connect:
Ost.connect port: 6380, db: 2
Then you only need to refer to a queue for it to pop into existence:
Ost[:rss_feeds] << @feed.id
A worker is a Ruby file with this basic code:
require "ost"
Ost[:rss_feeds].each do |id|
...
end
It will pop items from the queue with a timeout of two seconds and retry indefinitely. If you want to configure the timeout, set the environment variable OST_TIMEOUT.
Available methods for a queue are push (aliased to <<) and pop (aliased to each).
Note that in these examples we are pushing numbers to the queue. As we have unlimited queues, each queue should be specialized and the workers must be smart enough to know what to do with the numbers they pop.
If the block raises an error, it is captured by Ost and the exception is logged in Redis.
Consider this example:
require "ost"
Ost[:rss_feeds].each do |id|
...
raise "Invalid format"
end
Then, in the console you can do:
>> Ost[:rss_feeds].push 1
=> 1
>> Ost[:rss_feeds].errors
=> ["2010-04-12 21:57:23 -0300 ost:rss_feeds:1 => #<RuntimeError: Invalid format>"]
Both Delayed::Job and Resque provide queues and workers (the latter using Redis). They provide dumb workers that process jobs, which are specialized for each task. The specialization takes place in the application side, and the job is serialized and pushed into a queue.
Ost, by contrast, just pushes numbers into specialized queues, and uses workers that are subscribed to specific queues and know what to do with the items they get. The total sum of logic is almost the same.
$ gem install ost
Copyright (c) 2010 Michel Martens
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