redis memory increasing linearly

[Anders Håål]

Hi Francesco,

Redis memory will increase with the number of data points you collect 
and how long time you configured to keep them.

So what was the memory before it started to grow? Was it steady on this 
level? How much is it growing? And not using the redis instance for 
anything else? (redis-cli info)

It's a good sign that your memory is the same between restarts, since 
that means that the redis persistence works.

Have you restarted bischeck after the 20 Nov?

When it comes to the memory config in redis there are a number of 
strategies to manage memory, but in the bischeck setup redis is used as 
a data store and not as a cache, so you would not like to have any 
eviction polices. Setting max-memory will just make any write fail when 
redis is at its max-memory.

I think its safe to upgrade redis to a later version, but please try it 
first. Currently I run bischeck on 4.0.2 without problem. At the same 
time I do not think this is a redis bug.

To track what goes on in the your redis instance you can check with 
redis-cli. Every servicedefinition becomes its own list in redis. You 
can check the size (llen) of the list and see if its relates to your 
purge configuration. You can also read the first and last entities in 
the list to check the time stamp (lrange). Depending on the bischeck 
config you may also have additional lists for the servicedefinition for 
aggregrations.

/Anders


On 12/04/2017 10:11 AM, Francesco Giuseppe Toffoli wrote:
>
> Hi everybody,
> since a coupe of weeks the memory used by Redis in increasing 
> linearly, continuosly.
> We are a bit worried as also after a Redis server restart the 
> situation is the same (the RAM taken is equal before and after the 
> restart).
> I would exclude the issued has been caused by a configuration change, 
> the issue started on 20 November at 11:44PM when nobody was working on 
> bischeck.
> I'm enabling logs in order to see if there is something wrong.
>
> In the meanwhile does anyone have a suggestion on how to proceed?
> Upgrading to Redis 4.0 (stable) can be done maintaining the 
> retro-compatibility with Bischeck? (we have Redis 2.8.23)
>
>
> As a workaround I was thinking to enable the Redis option 'maxmemory' 
> with the 'maxmemory policy': about this last option, as we need all 
> keys to be maintained on database, does anyone know as can be set? 
> (I've read something about key eviction but i still don't have any 
> clear idea).
>
>
> Regards,
> Francesco
>
>
> -- 
>
> Francesco Giuseppe Toffoli
> Monitoring Engineer
>
> GSE Department
>
> Tel: +39 01127387488
>
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