When a Web Agent is reporting the following error:
[28785/3076462880][Thu Jan 01 2009 12:30:09][SmClient.cpp:1798][ERROR] Response time is negative,
can not update performance stats.
What is the precise meaning of this error?
To keep track of the performance of the policy server, the web agent calculates the response time for every request sent to the policy server and accordingly updates the performance statistics.
The system clock functions are used at the start of the Web Agent request to the Policy Server and after request completion, to compute the time taken by the Policy Server to process the request.
The difference in the two timings recorded gives the response time of the Policy Server, from the Web Agent's point of view.
The above error message is logged when the response time is found to be negative (though this should not happen ideally) and due to this web agent does not update the performance stats. The response time can possibly come out to be negative if system clock function fails to fetch the current time and on failure the system call returns -1.
The error simply implies that the response time for the current request came out to be negative (possibly due to momentary failure of system clock function) and so performance stats for a particular Policy Server will not be updated with the data from the request.