Add monitors.d directory + config to default configuration

[andrewvc]

This makes heartbeat much easier to use by default, and less confusing in terms of where/how
to create this directory.

[andrewvc]

For any reviewers out there, how can we test this in the context of apt/deb to make sure those packages add the same files to the directory layout?

[andrewkroh]

For each package type you’ll need to apply a bit of customization to add your monitors.d directory to the package. Take a look at the magefile.go for filebeat/metricbeat/auditbeat for an example.

After building the packages (mage package) we execute a test that checks the contents of each package type. We have a way of checking for modules.d in each package type. Maybe you could change the existing checks to be configurable (like allow monitors.d to be changed to monitors.d via a CLI flag). See
https://github.com/elastic/beats/blob/master/dev-tools/packaging/package_test.go#L61.

Hopefully this will get you started. I’m happy to chat after you’ve taken a look at this stuff.

[elasticmachine]

Pinging @elastic/uptime

[ruflin]

@andrewvc Anything I can help with to push this PR forward?

[andrewvc]

@ruflin not quite ready for review yet. I just rebased it and added support in the magefile.
I still need to write tests (and manually test it).

Also fixed heartbeat.yml to point at a relative path

[andrewvc]

OK, things seem to work and package tests are added. I actually haven't manually tested them yet. Can do tomorrow.

There's a lot of opportunity to DRY things up in the package tests, but it feels premature to me for the effort. WDYT @ruflin / @andrewkroh ?

[ruflin]

@andrewvc Code LGTM. Would be good if you could also test it locally and after merging keep an eye on the packaging tests.

In case you rebase again on master or do an additonal push, could you also make Hound happy? CI failures are not related.

[andrewvc]

@ruflin I tested this on OSX/Ubuntu Server/Fedora VMs using .tar.gz/.deb/.rpm respectively .

Everything worked great. On the linux box I set things up as a service using ES as a service. All I had to do to get a working monitor was remove the .disabled from a monitor in the sample dir and customize it to my liking.

I've improved the PR somewhat adding separate sample files per protocol to monitors.d.

[andrewvc]

jenkins, please retest this

looks like weird transient yum/docker issues

[ruflin]

CI failure do not seem to be related and the ones failing are "in the works" AFAIK.

[andrewvc]

@ruflin I've set reload: false as the default, squashed and rebased as well. LMK when we're good to merge.

[ruflin]

CI failures are not related.