switch to go-kit logger

[jkroepke]

Fixes #979
Replaces #987

See

• switch to go-kit logger prometheus/node_exporter#1575
• Make per-probe logs more accessible and useful prometheus/blackbox_exporter#218
• Switch to go-kit for logs. prometheus/mysqld_exporter#433

for similar changes

depends on

• Allow custom log.Logger prometheus/common#474
• Add Windows Eventlog logger go-kit/log#31

---

This is a breaking change for the log.format CLI flags.

• --log.format logger:stderr -> --log.file stderr --log.format logfmt
• --log.format logger:stdout?json=true -> --log.file stdout --log.format json
• --log.format logger:eventlog?name=windows_exporter -> --log.file eventlog

The breaking change happens on node_exporter before version 1, too. They dont add any backwards compability.

windows_exporter is still < version 1. In terms of semver, a breaking change is fine here.

[jkroepke]

@breed808 can you do take a look here?

[jkroepke]

@breed808 I would appreciate a review here.

[jkroepke]

rebased

[jkroepke]

@breed808 I would appreciate a review here, please let me know, if I can assist here.

[breed808]

Apologies for my absence in reviewing this. Thanks very much for the time and effort you've put into this change, it's another really good PR 😄

I've left a few minor comments, but aside from those I have no issues with change proposed by this PR.

[jkroepke]

I addressed all your changes. I hope thats fine now.

[breed808]

Looks good, thanks for integrating those changes 👍