I have a client/server system, one mina app is the client, one the
server.
I'm using my own decoders and encoders to send byte arrays over the
wire instead of using serialization.
Its almost exactly like the example of the image server:
http://mina.apache.org/tutorial-on-protocolcodecfilter-for-
mina-2x.html
I have the server hardcoded to send back a byte array of a known
size, the same one, over and over, its 68 bytes.
The client makes a Request object, its encoder writes out to the
wire, the decoder on the server side decodes that, services it in a
handler, makes a Response object, which is then encoded for the wire,
the client reads that in using its decoder and its done.
The problem is, after exactly 482 request/responses, each which occur
in basically .2ms each on my local machine as expected, all of a
sudden the client waits for nearly 180ms but without cpu being
consumed very much, as if one or other sides are in sleeps. 482*68
is almost exactly 32k.
If I shrink the # of bytes sent over, it runs fast more times, but
always until the total # of bytes sent back adds up to 32k.
The request is a 1byte command and the response is the byte array of
a string.
After a slow response, there are 3 more slow responses and then it
works fast again... until the 32k mark is hit again, and then a few
slow ones. it continues like that 482 fast back and forths, then 3
or 4 slow ones of about 200ms each, then 482 fast ones, etc.
Its all over the same socket.
I cant find in the mina code any 32k settings.
I thought perhaps it was related to a buffer being autoexpand or
autoshrunk but I havent been able to research that theory.
The most perplexing thing is that the cpu during the slow ones is
nearly idle, there's no disk activity, so its as if its network
blocking. When running the whole thing, it does not run full cpu
like it should, it uses a an average of about 15% only.
One thing I am doing that I'm not sure is allowed is using TWO
IoBuffers to write out to the stream during encoding, like this:
IoBuffer sizeBuf = IoBuffer.allocate(4, false);
sizeBuf.putInt(b.length);
sizeBuf.flip();
out.write(sizeBuf);
IoBuffer dataBuf = IoBuffer.wrap(b);
out.write(dataBuf);
this constitutes the entire response from the server. it writes 4
bytes and then it writes the contents of a byte buffer b.
It works, I read 4 bytes on the client and then i read the byte[].
I don't think its java 1.6 specific or mac specific (on an intel mac,
10.4.x, jdk 1.6) because I get the same behavior from a redhat linux
box I tried this on, both still talking to each other through the
localhost interface.
Does *anyone* have *any* ideas ??
Thanks,
Drew
