David Robakowski created THRIFT-2110:
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             Summary: Erlang: Support for Multiplexing Services on any 
Transport, Protocol and Server
                 Key: THRIFT-2110
                 URL: https://issues.apache.org/jira/browse/THRIFT-2110
             Project: Thrift
          Issue Type: Sub-task
          Components: Java - Library
            Reporter: David Robakowski
             Fix For: 0.9.1


*Motivation and Benefits*

We plan to use Thrift with a large number of functions communicating among (at 
least) three languages.  To keep maintainability high, we hope to avoid a 
single service defined with a large number of functions.  This would require 
monolithic, unwieldy service implementations as the number of functions grows.

Breaking up our API into multiple IDLs gives us multiple abstract base classes, 
which provides more flexibility in the object-oriented design of our server 
platform.

Before our changes, the alternative was to open up additional ports with 
smaller service implementations on each.  We'd rather not open additional ports.

*Our Approach*

We pursued an approach with the following in mind:

- No modifications to existing Thrift code.
- No modification to the Thrift protocol as described in the whitepaper.
- No modification to any {{TServer}}, {{TProtocol}} or {{TTransport}}.
- No need for any new {{TServer}} implementation.  Works with any {{TServer}} 
implementation.
- Work with any combination of {{TServer}}, {{TProtocol}} or {{TTransport}}.
- Avoid language-specific features, to ease implementation in other languages.

*Additions to Thrift*

Convenience class:
- {{TProtocolDecorator}} (extends {{TProtocol}}).  This is a no-op decorator 
around the {{TProtocol}} abstract class.

For use by clients:
- {{TMultiplexedProtocol}} (extends {{TProtocolDecorator}}).  This decorates 
any {{TProtocol}} by modifying the behaviour of {{writeMessageBegin(TMessage)}} 
to change {{TMessage.name}} from {{function_name}} to {{service_name + 
separator + function_name}}.

For use by the server:
- {{TMultiplexedProcessor}} (implements {{TProcessor}}).  It should be used to 
communicate with a client that was written using {{TMultiplexedProtocol}}.  It 
removes {{service_name + separator}} from {{TMessage.name}}, turning it back 
into the standard message format.  It then brokers the service request to the 
{{TProcessor}} which is registered to handle requests for that service.

*Sample Usage - Client*

In this example, we've chosen to use {{TBinaryProtocol}} with two services: 
{{Calculator}} and {{WeatherReport}}.

{code}
TSocket transport = new TSocket("localhost", 9090);
transport.open();

TBinaryProtocol protocol = new TBinaryProtocol(transport);

TMultiplexedProtocol mp = new TMultiplexedProtocol(protocol, "Calculator");
Calculator.Client service = new Calculator.Client(mp);

TMultiplexedProtocol mp2 = new TMultiplexedProtocol(protocol, "WeatherReport");
WeatherReport.Client service2 = new WeatherReport.Client(mp2);

System.out.println(service.add(2,2));
System.out.println(service2.getTemperature());
{code}

*Sample Usage - Server*

{code}
TMultiplexedProcessor processor = new TMultiplexedProcessor();

processor.registerProcessor(
    "Calculator",
    new Calculator.Processor(new CalculatorHandler()));

processor.registerProcessor(
    "WeatherReport",
    new WeatherReport.Processor(new WeatherReportHandler()));

TServerTransport t = new TServerSocket(9090);
TSimpleServer server = new TSimpleServer(processor, t);

server.serve();
{code}


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