[THRIFT-5547] C++ - Can't interrupt the handler on the server side while using TMultiplexedProcessor in case of client deconnection

• Type: Brainstorming
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 0.16.0
• Component/s: C++ - Library

Language

C++

• Assignee: Unassigned
• Reporter: julien greard
• Created: 05/Apr/22 06:43
• Updated: 05/Apr/22 06:45

Description

Hello,

I have the following architecture in my code:

 * 1 thrift Server
 * 1 thrift MultiplexedProcessor
 * several Services & associated processors/handlers
 * N thrift clients (several by processor/handler)
 * 1 queue which contains the tasks asked by the clients

What I*really*want is to be able cancel a task when a client crashes.

Let me explain:

Let's say I have the following service handler method :

// inside thrift handler // this method is currently instanciated once and called by every client void do_stuff(const std::string& parameter) { auto task = make_task(parameter); auto future_result = task .get_future(); add_to_queue(task); auto status = resultFuture.wait_for(timeout); // wait here until the task is over if (status != std::future_status::timeout) {     return future_result.get(); } }

If the client crashes/disconnects, there is no need to process with the task anymore, so I would like to cancel it (remove from my queue) asap.

To do so, I had the following ideas:

1/ Using the*setServerEventHandler*method from my Thrift Server to be notified when a client disconnects (deleteContext method). It works very well but I am not able to know which request was made by which specific client: within my handler I do not have access to the client infos, and I can't use (or didnt managed to) the void * context created by the method creatContext in my ServerEventHandler

2/ Using the contructor & destructor of my handler object to link 1 client to 1 handler. Then when the client disconnects, I only have to cancel every task he asked in the handler destructor. Currently I have N client and 1 handler, so it doesn't work. I figured I could use a TMultiplexedProcessorFactory but there is no such class in thrift. The TMultiplexedProcessor has to register Processor (with single handler) when I'd like to register a Factory which will create one handler instance by client. I could implement my own TMultiplexedProcessorFactory but I think there might be a good reason this doesn't exist yet.

Any idea of what I should do ?

I can post it inhttps://issues.apache.org/but it's not exactly an issue with thrift (great lib btw), rather than a question.

Thanks in advance, don't hesitate to ask for more details

This post is a duplicate of a StackOverflow question I asked last Friday <https://stackoverflow.com/questions/71707726/using-a-processor-factory-with-tmultiplexedprocessor-in-thrift>

Thanks in advance,

Julien Greard 

 

 

There has been an answer to this request in [e-mail] : the user Yuxuan Wang has described having the same issue in Go and he solved it by adding  a context to the handler services + a thread watchding regularly the opened sockets