[DIRMINA-1013] Threading model is supressed by ProtocolCodecFilter

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.0.9
• Fix Version/s: 2.0.10
• Component/s: Core, Filter
• Environment: Windows 7 x32 ; Java(TM) SE Runtime Environment (build 1.8.0_45-b14) ; Java HotSpot(TM) Client VM (build 25.45-b02, mixed mode, sharing)
• Flags: Important
• Assignee: Unassigned
• Reporter: Marat Gainullin
• Created: 04/Jun/15 14:26
• Updated: 07/Dec/15 09:53
• Resolved: 07/Dec/15 09:53

Description

ProtocolCodecFilter.messageReceived uses a semaphore to protect the following critical section:

                lock.acquire();
                // Call the decoder with the read bytes
                decoder.decode(session, in, decoderOut);
                // Finish decoding if no exception was thrown.
                decoderOut.flush(nextFilter, session);
                ...

in such fragment of code:

        // Loop until we don't have anymore byte in the buffer,
        // or until the decoder throws an unrecoverable exception or
        // can't decoder a message, because there are not enough
        // data in the buffer
        while (in.hasRemaining()) {
            int oldPos = in.position();
            try {
                lock.acquire();
                // Call the decoder with the read bytes
                decoder.decode(session, in, decoderOut);
                // Finish decoding if no exception was thrown.
                decoderOut.flush(nextFilter, session);
            } catch (Exception e) {
                ProtocolDecoderException pde;
                if (e instanceof ProtocolDecoderException) {
                    pde = (ProtocolDecoderException) e;
                } else {
                    pde = new ProtocolDecoderException(e);
                }
                if (pde.getHexdump() == null) {
                    // Generate a message hex dump
                    int curPos = in.position();
                    in.position(oldPos);
                    pde.setHexdump(in.getHexDump());
                    in.position(curPos);
                }
                // Fire the exceptionCaught event.
                decoderOut.flush(nextFilter, session);
                nextFilter.exceptionCaught(session, pde);
                // Retry only if the type of the caught exception is
                // recoverable and the buffer position has changed.
                // We check buffer position additionally to prevent an
                // infinite loop.
                if (!(e instanceof RecoverableProtocolDecoderException) || (in.position() == oldPos)) {
                    break;
                }
            } finally {
                lock.release();
            }
        }

Using of semaphore

public class ProtocolCodecFilter extends IoFilterAdapter {
...
    private final Semaphore lock = new Semaphore(1, true);

pushs other threads to wait while one of them is decoding. In MINA 2.0.7 there was a synchronized block at the same place, but on other point - decoderOut, wich is created per ioSession. Thus it was a stripped lock.

Issue Links

• is related to: DIRMINA-934 Replace synchronized with a Semaphore for better performance