Class: OpenWFE::Extras::SqsListener

Inherits:
Service
  • Object
show all
Includes:
MonitorMixin, Schedulable, WorkItemListener
Defined in:
lib/openwfe/extras/listeners/sqslisteners.rb

Overview

Polls an Amazon SQS queue for workitems

Workitems can be instances of InFlowWorkItem or LaunchItem.

require 'openwfe/extras/listeners/sqslisteners'

ql = OpenWFE::SqsListener("workqueue1", engine.application_context)

engine.add_workitem_listener(ql, "2m30s")
    #
    # thus, the engine will poll our "workqueue1" SQS queue
    # every 2 minutes and 30 seconds

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(queue_name, application_context) ⇒ SqsListener

Returns a new instance of SqsListener.



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# File 'lib/openwfe/extras/listeners/sqslisteners.rb', line 81

def initialize (queue_name, application_context)

    @queue_name = queue_name.to_s

    service_name = "#{self.class}::#{@queue_name}"

    super(service_name, application_context)

    linfo { "new() queue is '#{@queue_name}'" }
end

Instance Attribute Details

#queue_name ⇒ Object (readonly)

The name of the Amazon SQS whom this listener cares for



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# File 'lib/openwfe/extras/listeners/sqslisteners.rb', line 79

def queue_name
  @queue_name
end

Instance Method Details

#decode_object(message) ⇒ Object

Extracts a workitem from the message’s body.

By default, this listeners assumes the workitem is stored in its “hash form” (not directly as a Ruby InFlowWorkItem instance).

LaunchItem instances (as hash as well) are also accepted.



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# File 'lib/openwfe/extras/listeners/sqslisteners.rb', line 138

def decode_object (message)

    o = Base64.decode64(message.message_body)
    o = YAML.load(o)
    o = OpenWFE::workitem_from_h(o)
    o
end

#trigger(params) ⇒ Object

Will ‘find’ files in the work directory (by default ./work/in/), extract the workitem in them and feed it back to the engine.



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# File 'lib/openwfe/extras/listeners/sqslisteners.rb', line 96

def trigger (params)
    synchronize do

        ldebug { "trigger()" }

        qs = SQS::QueueService.new

        qs.create_queue(@queue_name)
            # just to be sure it is there

        while true

            l = qs.get_messages(
                @queue_name, :timeout => 0, :count => 255)

            break if l.length < 1

            l.each do |msg|

                o = decode_object(msg)

                handle_item o

                msg.delete

                ldebug do 
                    "trigger() " +
                    "handled successfully msg #{msg.message_id}" 
                end
            end
        end
    end
end