metrics: add collectd exporter metrics excluding [ch1233] (#5)

This change allows the `collectd` metrics exporter to be configured to
exclude specific metrics using a pattern matching system.

README.md

@@ -16,7 +16,7 @@ It can also be configured through a YAML file.
 Currently, due to a technical limitation, if a key is unknown, it will
 just be ignored. Be extra-careful that all keys are correctly spelled.
 
-## Yaml
+## Configuration
 
 The reporter encompasses the following aspects, each of them having its
 own subsection:
@@ -69,6 +69,11 @@ reporting:
  metrics:
  - expvar:
  listen: 127.0.0.1:8123
+ - collectd:
+ connect: 127.0.0.1:25826
+ interval: 10s
+ exclude:
+ - go.runtime.*
 ```
 
 The support outputs are:
@@ -107,6 +112,7 @@ The ``collectd`` output supports the following keys:
 
  - ``connect`` to specify the target (default to ``127.0.0.1:25826``)
  - ``interval`` to specify an interval (mandatory)
+ - ``exclude`` to specify a list of metric names patterns (shell globbing) to exclude from reporting
 
 For collectd output to work correctly, you need to append the
 following to ``types.db`` file::

metrics/collectd.go

@@ -3,6 +3,7 @@ package metrics
 import (
  "context"
  "os"
+ "path"
  "strings"
  "time"
 
@@ -21,6 +22,7 @@ var separator = "."
 type CollectdConfiguration struct {
  Connect config.Addr
  Interval config.Duration
+ Exclude []string
 }
 
 // UnmarshalYAML parses a configuration for collectd from YAML.
@@ -55,7 +57,7 @@ func (c *CollectdConfiguration) initExporter(m *Metrics) error {
  for {
  select {
  case <-tick.C:
- collectdReportOnce(m.Registry, client, time.Duration(c.Interval), m.prefix)
+ collectdReportOnce(m.Registry, client, time.Duration(c.Interval), m.prefix, c.Exclude)
  case <-m.t.Dying():
  break L
  }
@@ -69,7 +71,8 @@ func (c *CollectdConfiguration) initExporter(m *Metrics) error {
 }
 
 // collectdReportOnce will export the current metrics to collectd
-func collectdReportOnce(r metrics.Registry, client *network.Client, interval time.Duration, prefix string) {
+func collectdReportOnce(r metrics.Registry, client *network.Client, interval time.Duration,
+ prefix string, excluded []string) {
  ctx := context.Background()
  hostname, err := os.Hostname()
  if err != nil {
@@ -78,6 +81,14 @@ func collectdReportOnce(r metrics.Registry, client *network.Client, interval tim
  now := time.Now()
  vls := make([]*api.ValueList, 0, 10)
  r.Each(func(name string, i interface{}) {
+ // Filter metrics matching any configured pattern
+ // Any error parsing an exclusion pattern is silently ignored.
+ for _, pattern := range excluded {
+ if matched, _ := path.Match(pattern, name); matched {
+ return
+ }
+ }
+
  var identifierType string
  var values []api.Value
  switch metric := i.(type) {

metrics/collectd_test.go

@@ -39,6 +39,7 @@ func TestCollectd(t *testing.T) {
  configuration[0] = &CollectdConfiguration{
  Connect: address,
  Interval: config.Duration(500 * time.Millisecond),
+ Exclude: []string{"metrics.test.donot*"},
  }
  m, err := New(configuration, "project")
  if err != nil {
@@ -55,6 +56,9 @@ func TestCollectd(t *testing.T) {
  metrics.NewUniformSample(10)).Update(1871)
  metrics.NewRegisteredMeter("metrics.test.meter", m.Registry).Mark(19)
 
+ // Create a metric that we'll exclude from reporting
+ metrics.NewRegisteredGauge("metrics.test.donotwant", m.Registry).Update(13)
+
  // For timer, we would like to test percentiles too. 50 and 75
  // percentile will be 16, but others will be 18.
  tt := metrics.NewRegisteredTimer("metrics.test.timer", m.Registry)
@@ -193,6 +197,7 @@ L:
  },
  },
  }
+
  for _, c := range cases {
  found := false
  var v *api.ValueList
@@ -228,4 +233,10 @@ L:
  t.Errorf("Received metric %+v (-got +want):\n%s", v, diff)
  }
  }
+
+ for _, v := range values {
+ if v.PluginInstance == "donotwant" {
+ t.Error("Excluded metric found in received metrics")
+ }
+ }
 }