Re: Web Service slow on first call of the day

Each web service has a pool of host server jobs. In startup, the pool is
empty, As requests come in, host server jobs are instantiated and put in
the pool to be reused on subsequent requests.

At this time you would have to initiate a client request to populate the
pool.

In the future IBM is studying how to get around this by allowing users to
specify how many host server jobs should be put in the pool.






From: "Koester, Michael" <mkoester@xxxxxxxxxxxxx>
To: "midrange-l@xxxxxxxxxxxx" <midrange-l@xxxxxxxxxxxx>
Date: 03/09/2015 08:00 AM
Subject: Web Service slow on first call of the day
Sent by: "MIDRANGE-L" <midrange-l-bounces@xxxxxxxxxxxx>



(cross-posting to WEB-400)
I have developed a web service with the Integrated Web Services facility
(IWS) that is almost production ready, but I'm noticing that the very
first call of the day takes 30-45 seconds to return a response. A
subsequent calls provide sub-second responses, and that continues
throughout the day. I'm normally pretty patient, but this will be used to
provide data to a customer-facing web site, and if I was the first
customer of the day to the web site, I'd give up if it hung for more than
10 seconds -- by 30 seconds I'd be off doing other things for sure.

My questions are:
1. What are the likely causes for the delay-on-first-call behavior?
2. What might I do to either eliminate the problem, or perhaps simulate a
call on web server start-up, so that the first customer gets an acceptable
response time?

In our environment, we take down most subsystems overnight, for database
back-ups, for about 2 hours. When that completes, a n orderly CL-driven
start-up occurs, and the various subsystems are restarted and are ready
for action by about 4:30 AM. The web services are automatically active as
the web server comes up.

The web service itself calls an ILE-RPG program that calls a number of
service program procedures to gather data elements needed for the web site
presentation and navigation. Most of those procedures use embedded static
SQL. In my testing, I use the SOAPUI utility to simulate the calls that
the web site script would use, and it is with the SOAPUI calls that I
observe the delay in response on that first call.
My guess is that at least one component along the way takes a long time to
set up open data paths or something else that all the subsequent calls get
a free ride on, but I don't know enough about what goes on behind the IWS
curtain to know if there isn't an obstacle there.

All ideas are welcome. Let me know what other details might be helpful.
Thanks!

Michael Koester
Programmer/Analyst

DataEast