Updated Nov 26, 2007 by kookster

TenMinuteIntroduction

Start to finish example of sending and receiving

Ten Minute Introduction

We create a simple message consumer to receive messages, and a rails web controller that allows you to send a message when you click a button. This example uses the stomp adapter and an activemq message broker, but other brokers and adapters are now available.

Steps

Start ActiveMQ

bin/activemq

Create the rails application

rails demo

Add the activemessaging plugin

script/plugin install http://activemessaging.googlecode.com/svn/trunk/plugins/activemessaging

Create a processor

script/generate processor HelloWorld

This does the following if they don't exist already:

add the 'config/broker.yml' file to specify broker connections by environment
add the 'config/messaging.rb' file to map Stomp destinations to symbolic names
add the 'app/processor' folder where all prcessors that handle messages go
add the 'app/processor/application.rb' ApplicationProcessor class, parent to all processors

For your particular HelloWorld processor:

add the 'app/processor/hello_world_processor.rb'

By default, the processor will be subscribed to a queue ':hello_world'

class HelloWorldProcessor < ApplicationProcessor

  subscribes_to :hello_world

  def on_message(message)
    logger.debug "received: " + message
  end

end

If the generator created a new 'config/messaging.rb', it will have by default the queue symbol name to Stomp destination mapping:

    s.destination :hello_world, '/queue/HelloWorld'

Create a controller with an index action. We will use this to send our messages

script/generate controller SayHelloWorld index

Add the following to the new controller to allow us to access activemessaging

require 'activemessaging/processor'
include ActiveMessaging::MessageSender

publishes_to :hello_world

Modify the controller to send a message

def say_hello
  publish :hello_world, "<say>Hello World!</say>"
end

Add a button to send the message

<%=button_to "Say Hello", :action=>"say_hello" %>

Send a message. Browse to http://localhost:3000/say_hello_world and click the "Say Hello" button.

This adds a say action to the queue, which automatically gets created on first request.

Now, to begin consuming the queue, start the poller.rb script by running the poller daemon script:

script/poller run

The Processor logs the message to the console.

Comment by tieg.zaharia, Jul 13, 2007

Minor intro correction: it looks like the queue() method on the following line has been renamed to destination():

 s.queue :hello_world, '/queue/HelloWorld'

Comment by Tomasz.Wegrzanowski, Mar 18, 2008

'app/processor/hello_world_processor.rb' filename is wrong, it should be 'app/processors/hello_world_processor.rb'

Comment by james.wintermute, Jul 04, 2008

publishes_to :hello_world

This can be negated- indeed, it does not appear to exist. Argument to publish defines this.

Comment by sacketty, Sep 05, 2008

script/generate processor HelloWorld?

didn't work for me. I had a "class not found javax.jms.MessageListerner?" error I had to copy activemq-all-5.1.0.jar into the jruby/lib directory to fix it

Comment by l.rieder, Sep 23, 2008

How persistent are those messages?

Comment by erik.scheirer, Sep 27, 2008

Rails 2.1.0.

Followed the steps above exactly. Set the broker.yml to point at remote activeMQ. Ports, etc. all work, have run remote tests to it all day long, no issues.

I hit the 'say_hello_world' action URL in my browser, page comes up fine.

Started script/poller run just fine, no exceptions.

when click the 'say hello' button on the page, I get an exception:

"Template is missing

Missing template say_hello_world/say_hello.html.erb in view path /Users/me/code/ybur/deepdebate.with.activemessaging.test/deepdebate/app/views"

Comment by erik.scheirer, Sep 27, 2008

...so I added the template in app/views/say_hello_world/say_hello.html.erb as a copy of the index... that was there. Restarted mongrel cluster, hit first instance with the right url, got the page, clicked the 'say hello' button and nada on the console.

I checked the activeMQ Q itself for a queue/ named "HelloWorld?' and its there -- every time I press the 'say hello' button in the page I see the msgs send and msgs received # increasing by one, so its definitely going to the Q and back.

BUt no console output from 'script/poller run'

This is ruby 1.8.6 and still rails 2.1.0.

Thanks anyone who can verify or correct me, I am keen to start using this nifty too NOW !! ;-)

Comment by heru.on.merb, Nov 18, 2008

I try to generate processor but trap in error like this:

PS C:\temp\demo> ruby C:\temp\demo\script\generate processor HelloWorld? c:/ruby/lib/ruby/gems/1.8/gems/activesupport-2.1.2/lib/active_support/dependenci es.rb:276:in `load_missing_constant': uninitialized constant RI::Paths (NameErro? r)

from c:/ruby/lib/ruby/gems/1.8/gems/activesupport-2.1.2/lib/active_suppo

rt/dependencies.rb:468:in `const_missing'

from c:/ruby/lib/ruby/1.8/rdoc/ri/ri_options.rb:53 from c:/ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:27:in `ge

m_original_require'

from c:/ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:27:in `re

quire'

from c:/ruby/lib/ruby/gems/1.8/gems/activesupport-2.1.2/lib/active_suppo

rt/dependencies.rb:510:in `require'

from c:/ruby/lib/ruby/gems/1.8/gems/activesupport-2.1.2/lib/active_suppo

rt/dependencies.rb:355:in `new_constants_in'

from c:/ruby/lib/ruby/gems/1.8/gems/activesupport-2.1.2/lib/active_suppo

rt/dependencies.rb:510:in `require'

from c:/ruby/lib/ruby/1.8/rdoc/usage.rb:72
... 48 levels...
from c:/ruby/lib/ruby/gems/1.8/gems/rails-2.1.2/lib/commands/generate.rb

from c:/ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:27:in `ge

m_original_require'

from c:/ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:27:in `re

quire'

from C:/temp/demo/script/generate:3

from c:/ruby/lib/ruby/gems/1.8/gems/activesupport-2.1.2/lib/active_suppo

rt/dependencies.rb:468:in `const_missing'

from c:/ruby/lib/ruby/1.8/rdoc/ri/ri_options.rb:53 from c:/ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:27:in `ge

m_original_require'

from c:/ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:27:in `re

quire'

from c:/ruby/lib/ruby/gems/1.8/gems/activesupport-2.1.2/lib/active_suppo

rt/dependencies.rb:510:in `require'

from c:/ruby/lib/ruby/gems/1.8/gems/activesupport-2.1.2/lib/active_suppo

rt/dependencies.rb:355:in `new_constants_in'

from c:/ruby/lib/ruby/gems/1.8/gems/activesupport-2.1.2/lib/active_suppo

rt/dependencies.rb:510:in `require'

from c:/ruby/lib/ruby/1.8/rdoc/usage.rb:72
... 48 levels...
from c:/ruby/lib/ruby/gems/1.8/gems/rails-2.1.2/lib/commands/generate.rb

from c:/ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:27:in `ge

m_original_require'

from c:/ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:27:in `re

quire'

from C:/temp/demo/script/generate:3

I'm using rails 2.1.2 on windows.

Any suggestion ?

Comment by javajames, Nov 18, 2008

For those struggling like Erik did, the message seems to go to the Rails log, not the console, as it did for me. FYI.

Comment by bramski, Mar 30, 2009

Can you please add the requirement for "gem install reliable-msg" to this demo? Seems like that is a required gem of this particular plugin. The application throws a very nasty exception without this gem being installed. A quick google search brings up this forum posting:

http://markmail.org/message/qmt5wvmjs4oluwsw

And that should REALLy be documented here. Thanks and great work, this will save me a handful in debugging and testing our JMS services.

-Bram

Comment by bramski, Mar 30, 2009

"stomp" is apparently also a required gem.