Question & Answer
Provide guidelines on how to possibly monitor 3000 web servers. How many agents are required as a estimate to perform a 'http get', once a minute, on each server / application, to check its availability, and check the content for a specific string.
No detailed capacity planning figures in ITCAM for Tx - Internet Service Monitoring documentation.
To monitor basic web server http availability, the best possible solution using ITCAM for Transactions product would be to use the ISM (Internet Service Monitoring) type of agent and its "http monitor" feature.
A rough estimate to start with, and that would need to be refined during a trial or proof of concept, could be to set up at least 3 ISM agents in the environment, and configure 1000 "http monitors" simple tests on each ISM agent, to perform basic http get availability and check the content for a specific string.
But an estimate per ISM agent could be around 1000 "http monitors" simple tests per minute.
Of course these numbers can vary based on many factors, like hardware performance (CPU, network, network card) where the ISM agent is installed, and how quickly the web servers respond
As a base of work, on a basic AIX test system, querying a nearby web server plus a few failures, can run around 1000 tests per minute. Name look ups, delays, time-outs, redirects and other issues will decrease that figure.
There are also some settings that can be tuned to ensure better performance, like :
At the element level:
- keep timeouts to a minimum, say 3 seconds
- keep retries and retests set to 0
- keep the HTTP action limited to just GET or POST
- avoid hostnames that fail to resolve, DNS failures take up a lot of time
- keep regular expressions simple and to a minimum
At the monitor level (http.props):
- increase ConfigurationCheckInterval to avoid spending time checking
if the XML file has changed:
- keep FullHostInfo at 0 as it can waste up to a minute for each test
- increase MaxCCA to 50 tests concurrently
- set Pause to 10 milliseconds for less time between spawning threads
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17 June 2018