[jira] [Created] (THRIFT-1914) Python: Support for Multiplexing Services on any Transport, Protocol and Server

["Doug MacEachern (JIRA)" <ji...@apache.org>]

Doug MacEachern created THRIFT-1914:
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             Summary: Python: Support for Multiplexing Services on any Transport, Protocol and Server
                 Key: THRIFT-1914
                 URL: https://issues.apache.org/jira/browse/THRIFT-1914
             Project: Thrift
          Issue Type: New Feature
          Components: Java - Library
            Reporter: Doug MacEachern
             Fix For: 1.0


*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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