Hi Emmanuel,
not the gathering of the data is stopped. Instead (already successful) the
processed data
is repeatedly process again by my implementation of
class XXX extends MessageDecoderAdapter implements MessageDecoder {
…
public MessageDecoderResult decodable( final IoSession session,final IoBuffer
buffer ) {
try {
final int index =
CONTENT_LENGTH_HEADER.length();
if( buffer.remaining() < index )
return
MessageDecoderResult.NEED_DATA;
final CharsetDecoder
UTF_DECODER = StandardCharsets.UTF_8.newDecoder();
if(
!CONTENT_LENGTH_HEADER.equals( buffer.getString( index,UTF_DECODER ) ) )
return
MessageDecoderResult.NOT_OK;
final StringBuilder
contentLengthStr = new StringBuilder();
while( buffer.remaining() > 0 )
{
final byte
digit = buffer.get();
if( digit == LF
)
break;
contentLengthStr.append( (char)digit );
}
if( buffer.get() != LF )
return
MessageDecoderResult.NEED_DATA;
final int contentLength =
Integer.parseInt( contentLengthStr.toString().trim() );
if( buffer.remaining() <
contentLength )
return
MessageDecoderResult.NEED_DATA;
if( !decodeableXML(
session,buffer.getString( contentLength,UTF_DECODER ) ) )
return
MessageDecoderResult.NOT_OK;
return MessageDecoderResult.OK;
}
catch( final BufferUnderflowException buf ) {
buffer.reset();
return
MessageDecoderResult.NEED_DATA;
}
catch( final CharacterCodingException cce ) {
throw new RuntimeException(
cce.getMessage(),cce );
}
}
...
}
(Sorry I cannot post the whole code, but the code is more than 5 years old and
reliably working in production
environments.)
Thus I don’t use a limiter directly, it has a header the bytes is send of the
payload.
HTH
Max
From: Emmanuel Lecharny <[email protected]>
Date: Thursday, 24. July 2025 at 10:27
To: [email protected] <[email protected]>
Subject: Re: Possible bug in CumulativeProtocolDecoder
Hi Max,
if I understand correctly,n the message that the Handler receives may
contain more than one protocol message (m3 m4), as if the gathering of
data is not stopped?
I'll try to check the code, there may be something fishy...
Could you tell which limiter you use?
On 21/07/2025 11:20, Max Larsson wrote:
> Hi everyone,
>
> especially to Emmanuel for driving mina forward.
>
> I think I found a bug in mina core 2.1.10 in 2.1.9 I cannot reproduce it.
> It has to do with CumulativeProtocolDecoder class and I think it was
> introduced with the following patch:
> https://github.com/apache/mina/commit/88cb55397c414c6d09ce2d085ce912ab4bf45bf3
>
> The bug isn’t easily reproducible, so I will first describe how the bug
> expresses. Best to describe is
> A simple visualization. We have real messages t1 to tx which are really send
> via a TCP/IP connection
> And we have decoded message m1 to mx, which appears finally in the
> messageReceived method
> Of my IOHandler. During the communication the following happens “out of the
> blue”:
>
> t1 -> m1
> t2 -> m2
> t3 -> m3
> t4 -> m3 m4
> t5 -> m3 m4 m5
> …..
>
> I don’t know if it ever “resets” itself, because my business logic is getting
> panic at t4.
>
> The prerequisite for triggering this behaviour is that the MessageDecoder
> returns a NEED_DATA,
> but it isn’t always the case that a NEED_DATA triggers the behaviour.
>
> Now comes my observations:
>
>
> * The NEED_DATA converts the IoBuffer used into a session buffer
> * It copies un the unprocessed data into the session buffer
> * Waits for more data to received
> * No if new data arrives it is appended to the session buffer
> * The message encoder decodes the messages return OK
> * There aren’t any remaining bytes in the session buffer
> * Lets assume position in the session buffer is 256
> * Now the session buffer gets “freed”
> * If now new data arrives it is appended to the session buffer
> * Than flip gest called on the session buffer
>
> That sets the position of the buffer to 0, at that position is still
>
> The data from the previous successful decoded data.
>
>
>
> To “fix” it the position should either be set to 256 or the “freed”
>
> Operation should really discard the successful decoded data.
>
>
>
> HTH and is understandable. In doubt ask me.
>
>
>
> Kind regards
>
>
>
> Max
>
>
>
>
>
> Mit freundlichen Grüßen
> Best regards
>
> Dipl.-Inform. Max Larsson
> Geschäftsleitung
>
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