Non-Blocking I/O

Non-blocking I/O avoids the client being blocked while waiting for a request to be accepted by the transport layer during one-way messaging for connection-oriented protocols.

For connection-oriented protocols, there is a limit to the amount of data that can be put in a network protocol queue. The limit depends on the transport protocols used. When a client sending a request reaches the data limit, this client is blocked from processing until its request has entered the queue. You cannot determine how long a message will wait before being added to the queue.

In non-blocking I/O, when the transport queue is full, there is an additional buffer available between the client and the transport layer. As requests not accepted by the transport queue can be stored in this buffer, the client is not blocked. The client is free to continue processing as soon as it has put the request in the buffer. The client does not wait until the request is put in the queue and does not receive information on the status of the request after the buffer accepts the request.

By using non-blocking I/O you gain further processing time as compared to two-way and one-way messaging. The client can send requests in succession without being blocked from processing.

The following figure shows a case where you choose the non-blocking argument of the I/O mode and the transport layer queue is full.

Figure 8-3  Non-Blocking Messaging