Re: Web Service slow on first call of the day

[Nadir Amra <amra@xxxxxxxxxx>]

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