Hello,
I've just started with Mina and am facing a problem I've been stuck with
for days.
Environment:
- Mina 2.0.0 RC1
- Sun JDK 1.5 / 1.6 / 1.6 x64
- Windows Vista x64
I'm currently trying to switch an open source grid computing project
(http://www.jppf.org), of which I am a developer, to Mina's
communication framework, as I believe it would be easier to maintain and
extend, and I'm very excited by the built-in SSL and in-JVM
communication capabilities.
The architecture of the project is of type master / worker where the
master acts as the Mina server, and the worker nodes as the clients.
Currently, I am at a point where the communication between server and
client is working, but only with a single client/node. As soon as I have
more than one client, exceptions are thrown on the clients' side on
write operations.
Each message exchanged between server and client is made of a set of
serialized Java objects, with a header for each object which is a
4-bytes integer that indicates the length of the serialized block of
data. The first serialized object (i.e. message header) tells how many
objects are in the message.
Basically each message is as follows: [ length1, data1, ... , lengthN,
dataN ] where lengthX is the length of block dataX, which is a
serialized object graph.
From the tracing and debugging I've done, the first object is always
read and deserialized properly, and it is always on the second object
that the exceptions occur. The exceptions are of types
StreamCorruptedException, NegativeArraySizeException, OutOfMemoryError,
apparently due to the fact that the block length is not read or written
properly.
On the server side, serialization/deserialization occurs only for the
first (header) object of the message. The other objects are actually
handled as arrays of bytes, but not necessarily in memory: some or all
of them may be stored in temporary files, depending on the remaining
available memory in the server's JVM. The goal is to allow the server to
work with data structures that are much larger than the JVM heap. This
is why I implemented a custom IoFilter, rather than for instance a codec
like CumulativeProtocolDecoder, as I do not want the entire message to
be in memory (only the header object, which is relatively small, has to be).
Sorry for the lengthy explanation, I hope it is clear enough. I am
puzzled as to why this is working with a single client, but not with 2
or more. Would you have any idea as to where I can look, and as to what
I could have missed, overlooked, or done wrong?
Please let me know if you need more information or code snippets.
Sincerely,
-Laurent
