fix: align compliancy to Prometheus naming convention

[izonder]

Fixes #283

[dswarbrick]

There seems to be some confusion about how to expose a "good" Prometheus metric in this library. Take this example:

# HELP nodejs_active_handles Number of active libuv handles grouped by handle type. Every handle type is C++ class name.
# TYPE nodejs_active_handles gauge
nodejs_active_handles{type="WriteStream",component="billing-dc-traffic",worker="0"} 2
nodejs_active_handles{type="Server",component="billing-dc-traffic",worker="0"} 1
nodejs_active_handles{type="Timer",component="billing-dc-traffic",worker="0"} 2
nodejs_active_handles{type="Socket",component="billing-dc-traffic",worker="0"} 1

# HELP nodejs_active_handles_total Total number of active handles.
# TYPE nodejs_active_handles_total gauge
nodejs_active_handles_total{component="billing-dc-traffic",worker="0"} 6

Aside from the fact that the _total suffix in a the name of non-counter metric will trigger a warning about violating best practice naming conventions, the mere existence of this nodejs_active_handles_total is something of a Prometheus anti-pattern.

If I wanted a total of active handles (by component & worker), I could simply use the following promql query:

sum without (type) (nodejs_active_handles)

[SimenB]

@izonder CI is broken, which is why I haven't reviewed this yet.

---

@dswarbrick that was to avoid a breaking change, see discussion in #260. If there are other examples, we'd be happy to fix them 🙂

Merging this PR is also a breaking change, so we can clean up all names at once.

[izonder]

@SimenB please pay your attention there are some troubles with Node.js v6.x.x environment in Travis: https://travis-ci.org/siimon/prom-client/jobs/586419309

Seems the problem is out of the task scope.

[markmsmith]

Are CI issues still blocking this PR? I was kind of hoping all the renaming would settle before we roll out prometheus and have to deal with updating queries, alerts and graphs from these breaking changes.

[zbjornson]

The latest CI failures are real test failures that need to be addressed before this can be merged.

I haven't had a chance to look at this in depth though, considering #284 (comment) and the desire to clean up all metric names at once.

[WOLFinBULLcity]

It looks like the failed tests are potentially as simple as just needing to account for the addition of the timestamp property: https://travis-ci.org/siimon/prom-client/jobs/615513387?utm_medium=notification&utm_source=github_status

FAIL  test/clusterTest.js
  ● AggregatorRegistry › AggregatorRegistry.aggregate() › uses `aggregate` method defined for nodejs_eventloop_lag_seconds
    expect(received).toEqual(expected) // deep equality
    - Expected
    + Received
    @@ -4,9 +4,10 @@
        "name": "nodejs_eventloop_lag_seconds",
        "type": "gauge",
        "values": Array [
          Object {
            "labels": Object {},
    +       "timestamp": 1502075832298,
            "value": 0.0085,
          },
        ],
      }
      203 | 				.getSingleMetric('nodejs_eventloop_lag_seconds')
      204 | 				.get();
    > 205 | 			expect(ell).toEqual({
          | 			            ^
      206 | 				help: 'Lag of event loop in seconds.',
      207 | 				name: 'nodejs_eventloop_lag_seconds',
      208 | 				type: 'gauge',
      at Object.toEqual (test/clusterTest.js:205:16)

[sam-github]

I just checked this out, rebased it against master, and it passed. The last commit adds timestamp support, and all timestampe support is unneeded. So, I pushed that commit off my branch, and retested, and it passed.... that shows the last commit lacked unit tests! :-)

But, since it should be removed, it doesn't matter.

I didn't actually look at the output and run it pass the promtool checker, though, so I've no comment on the substance of the PR yet.

[sam-github]

The core problem here is that promtool thinks that anything called *_total should be COUNT, right, not a GAUGE? Would renaming to nodejs_active_handles also address this?

[izonder]

Every renaming is very easy to check with built-in prometheus "linter". Probably, it even could be a good idea just to add the linting as a job to CI pipeline

[RichardWright]

Do you need any help with this? I've love to pay it forward