Jim Suchy recently laid down some basics of Rinda in his blog Rinda
101. I would like to build on that and talk a little about the
process that is listening to the
tuplespace, waiting to
read or take messages.
tuple is written to the
rindlet will look at the message and determine if this
tuple of interest to it. If it is, then the engines
warm up and the
tuple gets processed by the logic in the
rindlet. Otherwise, the
rindlet will take a
pass, and wait for another message to be written to the
rindlets are autonomous and asynchronous pieces of
business logic that are messaging across many systems, or across many
modules of the same system. We deploy them as daemon processes.
As a proof of concept, Jim and I built a trivia game, with two different interfaces. One will be a rich client, developed using a Ruby framework called Limelight, and one will be a command line Ruby client.
Lets look at the code in the rich client application which updates the question on a screen for all the trivia participants to answer.
This code spawns a thread to sit and listen to the
server to see if there are any new questions. The questioner
rindlet will post a
tuple called “current
question” every 30 seconds to change the question. After we create a
rinda client, we set up the match criteria for the
tuples we are interested in.
We want to read all
tuples that match the fourth parameter,
which is the question text to display on the screen:
This example shows you can integrate your application with rinda. Your
application can listen to the
tuplespace to get messages
that are relevant only to it.
If you are writing a rails application, then you would have to use the view helper periodically call remote, since rails is single threaded, it isn’t as easy as firing a thread and moving on.
Lets start with some
with_standard_tuple method is a standard
wrapper to match elements and take the
tuple if it matches and
pass it into the block. Alternatively, you could do:
rindlet itself then gets the next question from the
game, and writes a
tuple back to the
tuplespace with a response, containing the question text.
Notice the code in this
rindlet feels like
MVC controller code.
rinda is a technology and notation of communication,
it will just call the business logic in the models and respond to the
actions performed if needed.
rindlets often behave as
system level controllers, not specific to any one application.
I have had lots of fun getting
rindlets to work, and they
have been an interesting tool for decoupling business logic from any