In many default installations ceph and varnish binaries require root
permissions or specific user permissions to actually gather metrics.
Although it's possible to instrumented system configuration to either
run telegraf with root privileges or share the same user/permissions as
measured software it's not a default setup.
In my opinion ability to run binary with `sudo` makes entire setup
simpler without additional interaction.
My changes allow to use configuration like:
```
binary = "/usr/bin/sudo /usr/bin/varnishstat"
ceph_binary = "/usr/bin/sudo /usr/bin/ceph"
```
With a proper sudo configuration it will simplify amount of changes
needed to collect metrics.
I've also changed type of varnish metrics. It was `int` but in varnish source
code we can find all metrics are actually uint64
(https://github.com/varnishcache/varnish-cache/blob/master/include/tbl/vsc_f_main.h)
I hit that issue with some metrics:
```
~# varnishstat -1 | grep -i MAIN.n_objectcore
MAIN.n_objectcore 18446744073709550877 . objectcore structs made
```
* Adding Varnish HTTP Cache input plugin
* Applying PR feedback
- Linked to varnish in input README
- Updated README/CHANGELOG
- Cleaned up sampleConfig to remove formatting
- Shorted lines to 80 chars (except where test input requires long strings)
- Using internal.RunTimeout to wrap call to varnishtat
- Added dummy file for windows
Lukasz Jagiello
robinpercy-xm