Messaging API supporting acknowledgements and request-response
Setup
- Inject the appropriate logger and set up connection parameters:
logger = Logger.new(STDOUT)
freddy = Freddy.build(logger, host: 'localhost', port: 5672, user: 'guest', pass: 'guest')
Supported message queues
These message queues have been tested and are working with Freddy. Other queues can be added easily:
Delivering messages
Simple delivery
Send and forget
Sends a message
to the given destination
. If there is no consumer then the
message stays in the queue until somebody consumes it.
freddy.deliver(destination, )
Expiring messages
Sends a message
to the given destination
. If nobody consumes the message in
timeout
seconds then the message is discarded. This is useful for showing
notifications that must happen in a certain timeframe but where we don't really
care if it reached the destination or not.
freddy.deliver(destination, , timeout: 5)
Request delivery
Expiring messages
Sends a message
to the given destination
. Has a default timeout of 3 and
discards the message from the queue if a response hasn't been returned in that
time.
response = freddy.deliver_with_response(destination, )
Persistant messages
Sends a message
to the given destination
. Keeps the message in the queue if
a timeout occurs.
response = freddy.deliver_with_response(destination, , timeout: 4, delete_on_timeout: false)
Errors
deliver_with_response
raises an error if an error is returned. This can be handled by rescuing from Freddy::InvalidRequestError
and Freddy::TimeoutError
as:
begin
response = freddy.deliver_with_response 'Q', {}
# ...
rescue Freddy::InvalidRequestError => e
e.response # => { error: 'InvalidRequestError', message: 'Some error message' }
rescue Freddy::TimeoutError => e
e.response # => { error: 'RequestTimeout', message: 'Timed out waiting for response' }
Responding to messages
freddy.respond_to destination do |, msg_handler|
# ...
end
The callback is called with 2 arguments
- the parsed message (note that in the message all keys are symbolized)
- the
MessageHandler
(described further down)
The MessageHandler
When responding to messages the MessageHandler is given as the second argument.
The following operations are supported:
responding with a successful response
msg_handler.success(response = nil)
responding with an error response
msg_handler.error(error: "Couldn't process message")
Tapping into messages
When it's necessary to receive messages but not consume them, consider tapping.
freddy.tap_into pattern do |message, destination|
destination
refers to the destination that the message was sent to- Note that it is not possible to respond to the message while tapping.
- When tapping the following wildcards are supported in the
pattern
:#
matching 0 or more words*
matching exactly one word
Examples:
freddy.tap_into "i.#.free"
receives messages that are delivered to "i.want.to.break.free"
freddy.tap_into "somebody.*.love"
receives messages that are delivered to somebody.to.love
but doesn't receive messages delivered to someboy.not.to.love
The ResponderHandler
When responding to a message or tapping the ResponderHandler is returned.
responder_handler = freddy.respond_to ....
The following operations are supported:
- stop responding
ruby responder_handler.shutdown
Notes about concurrency
freddy uses a thread pool to run concurrent responders. The thread pool is unique for each tap_into and respond_to responder. Thread pool size can be configured by passing the configuration option max_concurrency. Its default value is 4. e.g. If your application has 2 respond_to responders and 1 tap_into responder with max_concurrency set to 3 then your application may process up to 9 messages in parallel.
Note that while it is possible to use deliver_with_response inside a respond_to block, it is not possible to use another respond_to block inside a different respond_to block.
Note also that other configuration options for freddy users such as pool sizes for DB connections need to match or exceed max_concurrency to avoid running out of resources.
Read more from http://rubybunny.info/articles/concurrency.html.
Credits
freddy was originally written by Urmas Talimaa as part of SaleMove development team.
freddy is maintained and funded by SaleMove, Inc.
The names and logos for SaleMove are trademarks of SaleMove, Inc.