From 97c4780bc8c89b8cc0988c0acee8e22dab6792fb Mon Sep 17 00:00:00 2001
From: Marc Falzon <falzm@users.noreply.github.com>
Date: Fri, 1 Mar 2019 16:12:47 +0100
Subject: [PATCH] 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                |  8 +++++++-
 metrics/collectd.go      | 15 +++++++++++++--
 metrics/collectd_test.go | 11 +++++++++++
 3 files changed, 31 insertions(+), 3 deletions(-)

diff --git a/README.md b/README.md
index 56fc592..739ecd3 100644
--- a/README.md
+++ b/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::
diff --git a/metrics/collectd.go b/metrics/collectd.go
index 29a650a..74c37a7 100644
--- a/metrics/collectd.go
+++ b/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) {
diff --git a/metrics/collectd_test.go b/metrics/collectd_test.go
index 1593704..f897409 100644
--- a/metrics/collectd_test.go
+++ b/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")
+		}
+	}
 }