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

[Anil Madhavapeddy <anil@xxxxxxxxxx>]

On 16 Jun 2014, at 10:39, Thomas Gazagnaire <thomas@xxxxxxxxxxxxxx> wrote:

>> 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)

-anil


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