new flag to disable all default collectors (#1460)

* new flag to disable all default collectors

Signed-off-by: Paul Gier <pgier@redhat.com>

Co-authored-by: Ben Kochie <superq@gmail.com>

3 files changed, 36 insertions, 5 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index a109af1..f017b57 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -18,6 +18,7 @@
 * [CHANGE] Refactor mdadm collector #1403
 * [CHANGE] Add `mountaddr` label to NFS metrics. #1417
 * [CHANGE] Don't count empty collectors as success. #...
+* [FEATURE] New flag to disable default collectors #1276
 * [FEATURE] Add new schedstat collector #1389
 * [FEATURE] Add uname support for Darwin and OpenBSD #1433
 * [FEATURE] Add new metric node_cpu_info #1489
diff --git a/collector/collector.go b/collector/collector.go
index 0fec09c..e9ea14c 100644
--- a/collector/collector.go
+++ b/collector/collector.go
@@ -23,7 +23,7 @@ import (
         "github.com/go-kit/kit/log"
         "github.com/go-kit/kit/log/level"
         "github.com/prometheus/client_golang/prometheus"
-        "gopkg.in/alecthomas/kingpin.v2"
+        kingpin "gopkg.in/alecthomas/kingpin.v2"
 )
 
 // Namespace defines the common namespace to be used by all metrics.
@@ -50,8 +50,9 @@ const (
 )
 
 var (
-        factories      = make(map[string]func(logger log.Logger) (Collector, error))
-        collectorState = make(map[string]*bool)
+        factories        = make(map[string]func(logger log.Logger) (Collector, error))
+        collectorState   = make(map[string]*bool)
+        forcedCollectors = map[string]bool{} // collectors which have been explicitly enabled or disabled
 )
 
 func registerCollector(collector string, isDefaultEnabled bool, factory func(logger log.Logger) (Collector, error)) {
@@ -66,7 +67,7 @@ func registerCollector(collector string, isDefaultEnabled bool, factory func(log
         flagHelp := fmt.Sprintf("Enable the %s collector (default: %s).", collector, helpDefaultState)
         defaultValue := fmt.Sprintf("%v", isDefaultEnabled)
 
-        flag := kingpin.Flag(flagName, flagHelp).Default(defaultValue).Bool()
+        flag := kingpin.Flag(flagName, flagHelp).Default(defaultValue).Action(collectorFlagAction(collector)).Bool()
         collectorState[collector] = flag
 
         factories[collector] = factory
@@ -78,6 +79,28 @@ type NodeCollector struct {
         logger     log.Logger
 }
 
+// DisableDefaultCollectors sets the collector state to false for all collectors which
+// have not been explicitly enabled on the command line.
+func DisableDefaultCollectors() {
+        for c := range collectorState {
+                if _, ok := forcedCollectors[c]; !ok {
+                        *collectorState[c] = false
+                }
+        }
+}
+
+// collectorFlagAction generates a new action function for the given collector
+// to track whether it has been explicitly enabled or disabled from the command line.
+// A new action function is needed for each collector flag because the ParseContext
+// does not contain information about which flag called the action.
+// See: https://github.com/alecthomas/kingpin/issues/294
+func collectorFlagAction(collector string) func(ctx *kingpin.ParseContext) error {
+        return func(ctx *kingpin.ParseContext) error {
+                forcedCollectors[collector] = true
+                return nil
+        }
+}
+
 // NewNodeCollector creates a new NodeCollector.
 func NewNodeCollector(logger log.Logger, filters ...string) (*NodeCollector, error) {
         f := make(map[string]bool)
diff --git a/node_exporter.go b/node_exporter.go
index 6e92cc3..88039bd 100644
--- a/node_exporter.go
+++ b/node_exporter.go
@@ -29,7 +29,7 @@ import (
         "github.com/prometheus/common/version"
         "github.com/prometheus/node_exporter/collector"
         "github.com/prometheus/node_exporter/https"
-        "gopkg.in/alecthomas/kingpin.v2"
+        kingpin "gopkg.in/alecthomas/kingpin.v2"
 )
 
 // handler wraps an unfiltered http.Handler but uses a filtered handler,
@@ -153,6 +153,10 @@ func main() {
                         "web.max-requests",
                         "Maximum number of parallel scrape requests. Use 0 to disable.",
                 ).Default("40").Int()
+                disableDefaultCollectors = kingpin.Flag(
+                        "collector.disable-defaults",
+                        "Set all collectors to disabled by default.",
+                ).Default("false").Bool()
                 configFile = kingpin.Flag(
                         "web.config",
                         "Path to config yaml file that can enable TLS or authentication.",
@@ -166,6 +170,9 @@ func main() {
         kingpin.Parse()
         logger := promlog.New(promlogConfig)
 
+        if *disableDefaultCollectors {
+                collector.DisableDefaultCollectors()
+        }
         level.Info(logger).Log("msg", "Starting node_exporter", "version", version.Info())
         level.Info(logger).Log("msg", "Build context", "build_context", version.BuildContext())