Hi,
I haven't been updating you for a long time - I had really busy semester
at my university. Happily I've passed all the exams and now it's good
moment to continue working on what I picked some time ago, which is
Erlang binding.
I've created some base code which can be found under
sandbox/wjaniszewski. It implements:
1. Reference side - passing messages to Erlang nodes
2. Reference side - RPC
3. Service side - RPC
This code is dirty and needs much attention - especially for handling
non standard situations. However it's already good enough to show
intention and used mappings between Java and Erlang:
Rule 1. Each reference binding may be configured to communicate using
Erlang messaging system. Following reference can be only used to send
messages to node "MboxServer". Node can operate many message boxes, so
target message box name will be taken from method executed in referenced
object.
<reference name="mboxReference">
<tuscany:binding.erlang node="MboxServer" mbox="true"/>
</reference>
Rule 2. Each reference binding may be configured to be a RPC client to
certain program module (which is hosted on Erlang node and one Erlang
node may host many modules). Following reference can be only used to
execute functions declared in "hello" module on "RPCServer" node. Module
can contain many functions so target name will be taken from method
executed in referenced object. To access different modules separate
references should be created.
<reference name="moduleReference">
<tuscany:binding.erlang node="RPCServer" module="hello"/>
</reference>
Rule 3. Each service may be configured to be RPC server. If so then it
acts as program module on node - it's similar to rule 2, but reversed.
<service name="ServiceTest" promote="ServiceTest">
<interface.java interface="...ServiceTestComponent" />
<tuscany:binding.erlang node="RPCServer" module="hello"/>
</service>
Sample uses of this binding can be found in JUnit tests in
binding-erlang-runtime module.
I also have/had some problems, which are infrastructure related:
Problem 1. Erlang binding uses official jinterface library which I
didn't found in official maven repositories. It can be added locally to
maven repository, but it obviously breaks automation of building
project. What is your experience for such case?
Problem 2. Testing- Erlang uses Erlang Port Mapper Demon (epmd) to
register nodes etc. Epmd is standalone, non-java program and Erlang
binding tests needs it to be launched - it also can break automation of
building and testing project. I don't feel like rewriting it in Java ;)
Also having native Erlang nodes would be the best (not emulating them by
jinterface) and to do that we need to execute native erl binary. Any
thoughts?
I'll greatly appreciate any comments.
Thanks,
Wojtek
