Verint Community 11.1 - Cache monitoring

Verint Community (aka Telligent Community) 11.1 was released recently and had a couple of new features that caught my eye, so I decided to take a look and write about it here!

Last time I took a look at the blog workflows feature, this time I'm going to look at the new cache monitoring and how this could be useful to developers and administrators.

What is caching?

I'm not going to try answering this question in much detail here (there is plenty of information on your search engine of choice), but essentially it means keeping a copy of frequently used data in a way that is quicker to access than retrieving the data from storage each time.

In the Verint Community case this means keeping a copy in memory on the web and job server processes rather than calling SQL server each time, this gives better performance as getting the information from the cache is much faster than getting it from the database (and becomes more and more important the larger your site is).

The cache is limited in size to stop the server running out of memory, if too much data is added to the cache then somethings will have to be removed, which in turn can lead to worse performance as a database call will need to be made the next time the removed data is required.

What is the cache monitor?

The cache monitor is a new feature in version 11.1 which you can view by going to the administration area and clicking "Monitoring", then "Cache".

Clicking "Start" will start the cache monitoring session and after about 15 seconds you will see some details of the caches.

I'm running an install of 11.1 on my development machine with both the job server and web server running on the same machine.

Summary and Filters

The first section gives a summary of each community process that is running, how many hits (pieces of data that have been retrieved from the cache without having to call the database), how many misses (pieces of data that weren't in the cache so the database had to be called), how many items are in the cache in total, how much memory the cache is taking up and how much space it is allowed to use.

Hits and Misses

This graph shows a summary of the hits and misses over time, as people browse the site and the job service runs those numbers should change, ideally you want as many hits and as few misses as possible.

There are a few times you'd expect a large number of misses (such as when a site first starts up after a deployment/restart etc.) but if this happens continually this would be something to keep an eye on.

Memory Usage

The memory usage section shows how much memory each process is using for caching in comparison to the limit.

If you have a site with some content that isn't viewed often you may see jumps when a user or search engine hits them for the first time, and items will be cleared from the cache occasionally to ensure the data is up to date, other than this though once a site has been running for a little while without restarting I'd expect these to be pretty stable and not spike up and down too much.

Top Cache Hits and Misses

This shows the data items that have been requested a lot and if they were found in the cache or not. The name of these data items isn't particularly readable but might give you some idea of what is being looked at.

What if the cache gets too full?

If the cache gets too full you'll see the memory usage graph hitting (or maybe even going above) the maximum allowed memory for the cache, this will probably cause more cache hits and items are flushed from the cache and is likely to make your community slower.

If you have more memory (RAM) available on the servers hosting your community you can look at upping the cache limits by going to the administration area, selecting "Site" and then "Cache".

Here you can change the cache size limit, be careful when doing this and be sure to read and understand the details shown. In addition to this be aware this limit applies to all website and job processes so you'll need to ensure there is enough memory available on each of those servers for the increased cache size.

If you are at the max of your cache limit solutions become harder, you can look at removing old content, or upgrading the RAM available on the servers but that should be looked at on a case by case basis.

Summary

The new cache monitoring feature is Verint Community 11.1 could be a useful tool for developers and admins hitting performance problems with there community and when trying to plan server capacity for your community.

Ardour Digital can help you get the most out of Verint Community (aka Telligent Community). Providing development, training, and advice.

To find out more email hello@ardourdigital.co.uk or call +44 (0)177 3254 150.

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