Re: [MirageOS-devel] Monitoring MirageOS guests on CubieBoard2

[Thomas Gazagnaire <thomas@xxxxxxxxxxxxxx>]

>>> The medium-term goal is to sample the RRD stats into the Irmin git backend 
>>> (https://github.com/mirage/irmin) that Thomas Gazagnaire is working on.  
>>> This will let applications have a non-blocking stats delivery model via 
>>> RRD, and still provide a persistent data structure for long-term accrual of 
>>> data (e.g. via Git pushing to an aggregation server that isn't a tiny 
>>> embedded device).
>> 
>> I think we should be careful here. The main goal of RRD stats is to report 
>> long-running -- and possibly very intensive -- program stats with a bounded 
>> amount of memory. If you store the RRDs in irmin, you'll loose that 
>> property: your history will grow forever, possibly quite fast. I get you'll 
>> loose some performance as well as persistent arrays are less far efficient 
>> than the usual mutable arrays.
>> 
>> So yes, that's possible to store RRDs stats in irmin, but I'm not sure that 
>> what we really want usually in this scenario.
> 
> Agreed -- I was thinking about longer running analytics though.  RRDs 
> normally rotate and aggregate their statistics across a particular time 
> period, and ensure they are fixed size.
> 
> So we could either use the built-in RRD facility for this, or take advantage 
> of Irmin to take a distributed snapshot of all the VM's RRDs via an Irmin 
> commit (e.g. in order to figure out the total number of TCP connections 
> across a cluster).
> 
> This data would be pushed *off-cluster* into a bigger aggregation Irmin 
> database, so provides a way out of the RRD world into doing more analytics 
> (perhaps correlating these statistics with log files and other streaming data 
> sources that are also being fed into Irmin)

Ha right I see. That's indeed a good idea.

Thomas
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