Question

I have an input stream coming form a blackbox (say B). All the messages coming in from this stream are serialized binary data and each message starts with a four byte int. Most of it is logging data and runs 24 hrs a day. I read these four bytes using readInt() method. Now, ocasionally, the main thread would exit with EOFException and crash the program.

After researching on this, I found that it happens when there are less than four bytes in the input stream at the time of readInt(). My guess is that the buffer is not filling in fast enough between successive reads. Some of the possible solutions I am thinking of include checking available() before reading (consumes too many cycles considering the amt of data) or restart when exception occurs (sounds like poor programing). If only I could block using readInt(), it would be the best way, I think. I’ve looked at implementation of readInt() but again it boils down to blocking with read().

Anyone knows of a better solution?

Answer 1

Any blocking call down the call hierarchy is “bound” to make all the calls up the chain blocking as along as both calls are part of same thread of execution. The readInt method of DataInputStream makes four calls to the read method of the underlying input stream which will surely block as long as the data is not made available hence your fear of “buffer doesn’t fill in fast enough” doesn’t seem to be logical.

I have encountered these kind of exceptions in cases where either the server process dies or or drops the connection in which case the client ends up reading a -1 and throws an exception. Are you gobbling any sort of exceptions in your client/server code? Do your logs show anything suspicious?