QNX PPS Service

The QNX Persistent Publish/Subscribe (PPS) service is a small, extensible publish/subscribe service that offers persistence across reboots. It is designed to provide a simple and easy to use solution for both publish/subscribe and persistence in embedded systems, answering a need for building loosely connected systems using asynchronous publications and notifications.

With PPS, publishing is asynchronous: the subscriber need not be waiting for the publisher. In fact, the publisher and subscriber rarely know each other; their only connection is an object which has a meaning and purpose for both publisher and subscriber.

The QNX Smart Energy Reference uses PPS.

Running PPS

The PPS service can be run with the options listed below.

Syntax:

pps [options]

Options:

-b

Do not run in the background. Useful for debugging.

-l argument

Set the object load behavior, as follows:

• 0 — load directory names and objects on demand. Default.
• 1 — load all directory and object names on startup, but do not load object contents. Load object contents on demand.
• 2 — load directories, objects, and object contents on startup.

-m mount

Specify the mountpath for PPS. Default is /pps/

-p path

Set the path for backing up the persistent storage.

-t period

Specify the periodicity of the forced persistence, in milliseconds. For example -t 5000 forces the PPS service to write to persistent storage every five seconds. Default is no forced persistence.

-v

Enable verbose mode. Increase the number of “v”s to increase verbosity.