[THRIFT-5104] Forwarding callContext into methods of handler as very last parameter

• Type: Improvement
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Component/s: C++ - Compiler, C++ - Library
• Assignee: Unassigned
• Reporter: Nikolay Rapotkin
• Created: 19/Feb/20 13:51
• Updated: 20/Dec/20 14:28

Description

I faced with common issue: I want be able to check if sender is a authorized user and to know who she/he is. I Decided to provide some heads to every single call by Injecting authorization token. For this purpose i made a ProtocolWrapper that do stuff like the following:

uint32_t ProtocolWrapper ::writeMessageBegin_virt(const std::string& name, const MessageType type, const int32_t seqid)
{
  auto size = TProtocolDecorator::writeMessageBegin_virt(name, type, seqid);
  if (type == MessageType::T_CALL || type == MessageType::T_ONEWAY)
    size += TProtocolDecorator::writeString(token);
  
  return size;
}

 

Then It's needed to process request , take out this authorization token, change it on user information and provide access to it inside methods of a heandler.

Taking out authorization token from data stream is pretty easy to do. For instance TMultiplexProcessor does the same stuff. Or there is even a better way - providing a ProcessorEventHandler which operates callContext which can do this work.

But the accessing taken data inside methods of a handler appeared a very difficult thing because callContext CAN NOT really influence on a method call or method arguments!

So, the idea is to generate a handler interface which can take callContext of Processor for it's direct access.

 

For example from this thrift service definition

 

service SomeService {
  void someMethod(),
  void anotherMethod(
   1: int value,
  ),
}

would generate the following code:

 

 

class SomeServiceIf {
public:
  virtual ~SomeServiceIf() {}

  virtual void someMethod() = 0;             // usual
  virtual void anotherMethod(int value) = 0; // methods

  // virtual methods but
  // with default implementation
  // for backward compatibility
  virtual void someMethod(void* ctx) {
    someMethod();
  }
  virtual void anotherMethod(int value, void* ctx) {
     anotherMethod(value);
  }
}

 

 

This requires small change in a SomeServiceProcessor. It should call method with context.

But this change wont break an existing code because of forwarding calls to non-context methods by default.

Does it make any sense or there is a better way to do what I want?

 

you can look at prototype of this change in my fork

Issue Links

• links to: GitHub Pull Request #2180