I'd like to use multiple services on one transport ( Thrift )

Question

I'd like to create several services, and I want to use them with different identifiers. So I mean :

I've got a Users and Projects service . I want to use these at the same time.

I mean I can add more 'services' to the "handlermap" on xmlrpc.

http://ws.apache.org/xmlrpc/server.html

phm.addHandler("Users",
             Users.class); 
phm.addHandler("Projects",
               Projects.class);

I would like to do the same in the thrift.

Here is a simple example : test.thrift

typedef i64 UserId

struct Bonk
{
  1: string message,
  2: i32 type
}

struct Insanity
{
  1: map<Bonk, UserId> userMap,
  2: list<Bonk> xtructs
}



service ThriftTest
{
  void         testVoid(),
  string       testString(1: string test),
  byte         testByte(1: byte test),
  i32          testI32(1: i32 test),
  i64          testI64(1: i64 test),
  double       testDouble(1: double test),
  list<map<i32,i32>> testMap(1: map<i32,i32> test),
  map<string,string> testStringMap(1: map<string,string> test),
  set<i32>     testSet(1: set<i32> test),
  map<i32,map<i32,i32>> testMapMap(1: i32 test),
  map<UserId, map<i32,Insanity>> testInsanity(1: Insanity argument)
}

Then I create an implementatino, then add it to the instance of TServer .

Users.Processor users_proccesor = new Users.Processor(New UsersImpl());
Projects.Processor project_processor = new Projects.Processors(new ProjectsImp());
// I would like to add Users and Projects  
ThriftTest.Processor prc = new ThriftTest.Processor(new ThiftTestImp());
            TServerTransport serverTransport = new TServerSocket(9090);
            TServer server = new TSimpleServer(new Args(serverTransport).processor( prc ));

And here's my big problem, I can't add multiple instances of the server.

Thank you for your help in advance.

Answer 1

Multiplexed Services (in essence that's what you want to do here) are being integrated right now. There are already patches for a number of languages available, either already accepted or in the process of being reviewed.

https://issues.apache.org/jira/browse/THRIFT-563 is a good place to start.

PS: Reviewers and contributions are welcome ;-)

Answer 2

RPC invocation is transmitted over the wire in TMessage structure that doesn't have 'targetService' field. So there's no straightforward way to bind several services to a single port without adding this field to TMessage and recompiling thrift.

It's possible to do a hack by implementing custom TServer similar to TSimpleSever (or any other TServer).

Server should read target service in the loop and get corresponding processor:

      ...
      inputProtocol = inputProtocolFactory_.getProtocol(inputTransport);
      outputProtocol = outputProtocolFactory_.getProtocol(outputTransport);
      do {
        String target = inputProtocol.readString();
        processor = processorFactoryMap.get(target).getProcessor(client);
      while (processor.process(inputProtocol, outputProtocol));
      ...

Client should prefix each message with target service string. This can be done by wrapping TBinaryProtocol in a custom protocol:

public void writeMessageBegin(TMessage message) throws TException {
    wrapped.writeString(target);
    wrapped.writeMessageBegin(message);
}

The main disadvantage of this approach is losing interoperability with other clients. So, probably it's better either to start two different TServers on different ports, or define all methods in a single thrift service, and then delegate invocations to appropriate handlers.