Re: Time to replace the hit ratio with something more intuitive?

[Tollef Fog Heen]

]] Rob S 

| I'd also caution against replacing, as people may have monitoring
| against the old figures...

Given this number only is displayed in interactive mode and not oneshot
mode, people should not be running automated checks against it.  Also,
as this would be quite confusing to people running 2.0, it'll not be
backported.  And it'll be marked well in the documentation that the
behaviour has changed.

-- 
Tollef Fog Heen 
Redpill Linpro -- Changing the game!
t: +47 21 54 41 73
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Re: Time to replace the hit ratio with something more intuitive?

[Michael Fischer]

On Tue, Jan 19, 2010 at 1:40 PM, Rob S  wrote:

> Michael Fischer wrote:
>
>  On Tue, Jan 19, 2010 at 12:09 PM, Nils Goroll > sl...@schokola.de>> wrote:
>>
>>I am suggesting to amend (or replace ?) this figure by a ratio of
>>client
>>requests being handled by the cache by total number of requests.
>>In other words,
>>a measure for how many of the client requests do not result in a
>>backend request.
>>
>>
>> I vote for the replacement option.  In my view, the ratio should be (total
>> requests)/(requests satisfied from cache).
>>
> That'd give odd figures (eg 1.25), when you'd expect to see 0.8.  Can we
> flip it the other way up?
>

Oops!  Yes.

I'd also caution against replacing, as people may have monitoring against
> the old figures...
>

Well, under the current regime, the figures may lead to a false sense of
complacency since the hit ratio may be falsely high.  If changing it causes
additional alerts to be raised, they probably needed to know all along. :)

--Michael
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Re: Time to replace the hit ratio with something more intuitive?

[Rob S]

Michael Fischer wrote:
> On Tue, Jan 19, 2010 at 12:09 PM, Nils Goroll  > wrote:
>
> I am suggesting to amend (or replace ?) this figure by a ratio of
> client
> requests being handled by the cache by total number of requests.
> In other words,
> a measure for how many of the client requests do not result in a
> backend request.
>
>
> I vote for the replacement option.  In my view, the ratio should be 
> (total requests)/(requests satisfied from cache).
That'd give odd figures (eg 1.25), when you'd expect to see 0.8.  Can we 
flip it the other way up?

I'd also caution against replacing, as people may have monitoring 
against the old figures...

Rob
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Re: Time to replace the hit ratio with something more intuitive?

[Michael Fischer]

On Tue, Jan 19, 2010 at 12:09 PM, Nils Goroll  wrote:

> The varnishstat cache hit rate basically gives a ratio for how many
> requests
> being directed to the cache component of varnish have been answered from
> it. It
> does not say anything about the number of requests being passed onto the
> backend
> for whatever reason. So it is possible to see cache hit rates of 0.
> (99.99%)
> but still 99% of the client requests hit your backend, if only 1% of the
> requests qualify for being served from the cache.


> I am suggesting to amend (or replace ?) this figure by a ratio of client
> requests being handled by the cache by total number of requests. In other
> words,
> a measure for how many of the client requests do not result in a backend
> request.


I vote for the replacement option.  In my view, the ratio should be (total
requests)/(requests satisfied from cache).

--Michael
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Re: Time to replace the hit ratio with something more intuitive?

[Darryl Dixon - Winterhouse Consulting]

> Hi,
>
> in http://varnish.projects.linpro.no/ticket/613 I have suggested to add a
> measure to varnishstat which I thought could be called the "efficiency
> ratio".
>
> Here's how the two figures look like on a production system:
>
> Hitrate ratio:  10  100 1000
> Hitrate avg:0.9721   0.9721   0.9731
> Efficiency ratio:  10  100 1000
> Efficiency avg:0.9505   0.9522   0.9533
>
>  55697963   200.97   256.93 Client connections accepted
> 402992210  1518.81  1858.98 Client requests received
> 390022582  1471.82  1799.15 Cache hits
>  1549 0.00 0.01 Cache hits for pass
>   905363722.0041.76 Cache misses
>
>
> Now it's up to you, what do you think about this?

+1

regards,
Darryl Dixon
Winterhouse Consulting Ltd
http://www.winterhouseconsulting.com
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