Fix duplicated tags in InfluxDB

vendor/github.com/go-kit/kit/metrics/doc.go

@@ -1,23 +1,54 @@
-// Package metrics provides a framework for application instrumentation. All
-// metrics are safe for concurrent use. Considerable design influence has been
-// taken from https://github.com/codahale/metrics and https://prometheus.io.
+// Package metrics provides a framework for application instrumentation. It's
+// primarily designed to help you get started with good and robust
+// instrumentation, and to help you migrate from a less-capable system like
+// Graphite to a more-capable system like Prometheus. If your organization has
+// already standardized on an instrumentation system like Prometheus, and has no
+// plans to change, it may make sense to use that system's instrumentation
+// library directly.
 //
-// This package contains the common interfaces. Your code should take these
-// interfaces as parameters. Implementations are provided for different
-// instrumentation systems in the various subdirectories.
+// This package provides three core metric abstractions (Counter, Gauge, and
+// Histogram) and implementations for almost all common instrumentation
+// backends. Each metric has an observation method (Add, Set, or Observe,
+// respectively) used to record values, and a With method to "scope" the
+// observation by various parameters. For example, you might have a Histogram to
+// record request durations, parameterized by the method that's being called.
+//
+//    var requestDuration metrics.Histogram
+//    // ...
+//    requestDuration.With("method", "MyMethod").Observe(time.Since(begin))
+//
+// This allows a single high-level metrics object (requestDuration) to work with
+// many code paths somewhat dynamically. The concept of With is fully supported
+// in some backends like Prometheus, and not supported in other backends like
+// Graphite. So, With may be a no-op, depending on the concrete implementation
+// you choose. Please check the implementation to know for sure. For
+// implementations that don't provide With, it's necessary to fully parameterize
+// each metric in the metric name, e.g.
+//
+//    // Statsd
+//    c := statsd.NewCounter("request_duration_MyMethod_200")
+//    c.Add(1)
+//
+//    // Prometheus
+//    c := prometheus.NewCounter(stdprometheus.CounterOpts{
+//        Name: "request_duration",
+//        ...
+//    }, []string{"method", "status_code"})
+//    c.With("method", "MyMethod", "status_code", strconv.Itoa(code)).Add(1)
 //
 // Usage
 //
-// Metrics are dependencies and should be passed to the components that need
+// Metrics are dependencies, and should be passed to the components that need
 // them in the same way you'd construct and pass a database handle, or reference
-// to another component. So, create metrics in your func main, using whichever
-// concrete implementation is appropriate for your organization.
+// to another component. Metrics should *not* be created in the global scope.
+// Instead, instantiate metrics in your func main, using whichever concrete
+// implementation is appropriate for your organization.
 //
 //    latency := prometheus.NewSummaryFrom(stdprometheus.SummaryOpts{
 //        Namespace: "myteam",
 //        Subsystem: "foosvc",
 //        Name:      "request_latency_seconds",
-//        Help:      "Incoming request latency in seconds."
+//        Help:      "Incoming request latency in seconds.",
 //    }, []string{"method", "status_code"})
 //
 // Write your components to take the metrics they will use as parameters to
@@ -40,8 +71,14 @@
 //    api := NewAPI(store, logger, latency)
 //    http.ListenAndServe("/", api)
 //
+// Note that metrics are "write-only" interfaces.
+//
 // Implementation details
 //
+// All metrics are safe for concurrent use. Considerable design influence has
+// been taken from https://github.com/codahale/metrics and
+// https://prometheus.io.
+//
 // Each telemetry system has different semantics for label values, push vs.
 // pull, support for histograms, etc. These properties influence the design of
 // their respective packages. This table attempts to summarize the key points of
@@ -54,7 +91,7 @@
 //    expvar      1    atomic                 atomic                 synthetic, batch, in-place expose
 //    influx      n    custom                 custom                 custom
 //    prometheus  n    native                 native                 native
-//    circonus    1    native                 native                 native
 //    pcp         1    native                 native                 native
+//    cloudwatch  n    batch push-aggregate   batch push-aggregate   synthetic, batch, push-aggregate
 //
 package metrics