[Hawkular-dev] Availability (Service and UI)

[Michael Burman]

Hi,

We already have dependency to Google's Guava, so there's a well tested 
cache implementation (with filling strategies and eviction strategies) 
already. No need to reinvent this one ;)

   - Micke

On 17.02.2015 12:52, Heiko W.Rupp wrote:
>> Am 17.02.2015 um 10:21 schrieb Thomas Heute <theute at redhat.com>:
>> IMHO typically one would be happy with a check every 20s/30s or even a minute if the cost is "low", ie: the cost of the monitoring infrastructure is a small fraction of the infrastructure itself.
> We need to consider this at different levels.
>
> An agent may be able to determine process availability every second cheaply. This does not imply
> that it needs to forward that information every second to the server. And even if it did, it does not
> imply that we need to store a data point for every second.
>
> One thing we did never really fit into classical RHQ is caching.
> A Map<Long,Byte> for the last known state of a resource (*) can easily store the last known
> availability state for a huge number of resources. This way we would not need to query the
> database for each incoming point, but we'd look up the value in the cache and only store
> when it differs.
> Needs a bit more investigating + modelling to expire entries in the cache that do not get a
> data point every now and then and inform other subsystems (alerting) - that is not too heavy to implement.
> The agent can do similar caching for its resources and only forwarding when the state changes.
>
> This way we can scale to a lot of checks agent side without overwhelming server and data store.
>
>
> *) Yes I know we are currently using string IDs in many places. We may reconsider that for resource ids.
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