rtstatus backend counters.

[Arianna Aondio]

Hi everyone,
some time ago I wrote a vmod called
libvmod-rtstatus(https://github.com/varnish/libvmod-rtstatus).
this vmod has two functions:
1- rtstatus(delta): creates a json object containing different Varnish counters.
2- html(): this function is just a nice interface for the user, it
uses the json object provided by the other function and shows them in
a "nice" way (https://github.com/varnish/libvmod-rtstatus/blob/4.0/varnishstatus.png).
In function 2 some math is done on counters related to backends.

Now, I think having function 1 as part of std_vmod is a good idea,
having an overview on what is happening on backends can be very
important for understanding how Varnish works and debugging various
situations.
The json file collect all the counters we have in varnishstat, but
there are also new counters, such as:
*hitrate and load calculated on a delta time decided by the user.
*total amount of KB and KB/s sent to backends.
*total amount of KB and KB/s received from backends.
*piped KB.
*health of backends.
etc,etc...

Please note I'd like to move the math from function 2 to function 1 so
the json object will have counters and numbers ready to be used and
analyzed , if some users feel like using a nicer interface than the
raw json object they can write their own html/javascript or just use
the default one I provide on my github page, but that will be a
different vmod and a different story.

Comments much appreciated.


Arianna Aondio
Software Developer | Varnish Software AS
Mobile: +47 98062619
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