Class: EventMachine::ThreadedResource
- Inherits:
-
Object
- Object
- EventMachine::ThreadedResource
- Defined in:
- lib/em/threaded_resource.rb
Overview
= EventMachine::ThreadedResource
A threaded resource is a "quick and dirty" wrapper around the concept of wiring up synchronous code into a standard EM::Pool. This is useful to keep interfaces coherent and provide a simple approach at "making an interface async-ish".
General usage is to wrap libraries that do not support EventMachine, or to have a specific number of dedicated high-cpu worker resources.
== Basic Usage example
This example requires the cassandra gem. The cassandra gem contains an EventMachine interface, but it's sadly Fiber based and thus only works on 1.9. It also requires (potentially) complex stack switching logic to reach completion of nested operations. By contrast this approach provides a block in which normal synchronous code can occur, but makes no attempt to wire the IO into EventMachines C++ IO implementations, instead relying on the reactor pattern in rb_thread_select.
cassandra_dispatcher = ThreadedResource.new do Cassandra.new('allthethings', '127.0.0.1:9160') end
pool = EM::Pool.new
pool.add cassandra_dispatcher
# If we don't care about the result: pool.perform do |dispatcher| # The following block executes inside a dedicated thread, and should not # access EventMachine things: dispatcher.dispatch do |cassandra| cassandra.insert(:Things, '10', 'stuff' => 'things') end end
# Example where we care about the result: pool.perform do |dispatcher| # The dispatch block is executed in the resources thread. completion = dispatcher.dispatch do |cassandra| cassandra.get(:Things, '10', 'stuff') end
# This block will be yielded on the EM thread:
completion.callback do |result|
EM.do_something_with(result)
end
completion
end
Instance Method Summary collapse
-
#dispatch ⇒ Object
Called on the EM thread, generally in a perform block to return a completion for the work.
-
#initialize ⇒ ThreadedResource
constructor
The block should return the resource that will be yielded in a dispatch.
-
#shutdown ⇒ Object
Kill the internal thread.
Constructor Details
#initialize ⇒ ThreadedResource
The block should return the resource that will be yielded in a dispatch.
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# File 'lib/em/threaded_resource.rb', line 56 def initialize @resource = yield @running = true @queue = ::Queue.new @thread = Thread.new do @queue.pop.call while @running end end |
Instance Method Details
#dispatch ⇒ Object
Called on the EM thread, generally in a perform block to return a completion for the work.
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# File 'lib/em/threaded_resource.rb', line 68 def dispatch completion = EM::Completion.new @queue << lambda do begin result = yield @resource completion.succeed result rescue Exception => e completion.fail e end end completion end |
#shutdown ⇒ Object
Kill the internal thread. should only be used to cleanup - generally only required for tests.
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# File 'lib/em/threaded_resource.rb', line 83 def shutdown @running = false @queue << lambda {} @thread.join end |