prometheus: Implement mgmt_checkapply_total metric

Signed-off-by: Julien Pivotto <roidelapluie@inuits.eu>

lib/main.go

@@ -439,6 +439,7 @@ func (obj *Main) Run() error {
 			// pass in the information we need
 			newGraph.AssociateData(&resources.Data{
 				Converger:  converger,
+				Prometheus: prom,
 				Prefix:     pgraphPrefix,
 				Debug:      obj.Flags.Debug,
 			})

pgraph/actions.go

@@ -224,6 +224,12 @@ func (g *Graph) Process(v *Vertex) error {
 		// if this fails, don't UpdateTimestamp()
 		checkOK, err = obj.CheckApply(!noop)
 
+		if obj.Prometheus() != nil {
+			if promErr := obj.Prometheus().UpdateCheckApplyTotal(obj.Kind(), !noop, !checkOK, err != nil); promErr != nil {
+				// TODO: how to error correctly
+				log.Printf("%s[%s]: Prometheus.UpdateCheckApplyTotal() errored: %v", v.Kind(), v.GetName(), err)
+			}
+		}
 		// TODO: Can the `Poll` converged timeout tracking be a
 		// more general method for all converged timeouts? this
 		// would simplify the resources by removing boilerplate

prometheus/prometheus.go

@@ -21,7 +21,9 @@ package prometheus
 
 import (
 	"net/http"
+	"strconv"
 
+	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/promhttp"
 )
 
@@ -33,6 +35,9 @@ const DefaultPrometheusListen = "127.0.0.1:9233"
 // prometheus instance. Run Init() on it.
 type Prometheus struct {
 	Listen string // the listen specification for the net/http server
+
+	checkApplyTotal *prometheus.CounterVec // total of CheckApplies that have been triggered
+
 }
 
 // Init some parameters - currently the Listen address.
@@ -40,6 +45,20 @@ func (obj *Prometheus) Init() error {
 	if len(obj.Listen) == 0 {
 		obj.Listen = DefaultPrometheusListen
 	}
+	obj.checkApplyTotal = prometheus.NewCounterVec(
+		prometheus.CounterOpts{
+			Name: "mgmt_checkapply_total",
+			Help: "Number of CheckApply that have run.",
+		},
+		// Labels for this metric.
+		// kind: resource type: Svc, File, ...
+		// apply: if the CheckApply happened in "apply" mode
+		// eventful: did the CheckApply generate an event
+		// errorful: did the CheckApply generate an error
+		[]string{"kind", "apply", "eventful", "errorful"},
+	)
+	prometheus.MustRegister(obj.checkApplyTotal)
+
 	return nil
 }
 
@@ -57,3 +76,12 @@ func (obj *Prometheus) Stop() error {
 	// https://stackoverflow.com/questions/39320025/go-how-to-stop-http-listenandserve/41433555#41433555
 	return nil
 }
+
+// UpdateCheckApplyTotal refreshes the failing gauge by parsing the internal
+// state map.
+func (obj *Prometheus) UpdateCheckApplyTotal(kind string, apply, eventful, errorful bool) error {
+	labels := prometheus.Labels{"kind": kind, "apply": strconv.FormatBool(apply), "eventful": strconv.FormatBool(eventful), "errorful": strconv.FormatBool(errorful)}
+	metric := obj.checkApplyTotal.With(labels)
+	metric.Inc()
+	return nil
+}

resources/resources.go

@@ -33,6 +33,7 @@ import (
 	// TODO: should each resource be a sub-package?
 	"github.com/purpleidea/mgmt/converger"
 	"github.com/purpleidea/mgmt/event"
+	"github.com/purpleidea/mgmt/prometheus"
 
 	errwrap "github.com/pkg/errors"
 	"golang.org/x/time/rate"
@@ -58,6 +59,7 @@ type Data struct {
 	//Hostname string         // uuid for the host
 	//Noop     bool
 	Converger  converger.Converger
+	Prometheus *prometheus.Prometheus
 	Prefix     string // the prefix to be used for the pgraph namespace
 	Debug      bool
 	// NOTE: we can add more fields here if needed for the resources.
@@ -164,6 +166,7 @@ type Base interface {
 	Started() <-chan struct{}        // returns when the resource has started
 	Starter(bool)
 	Poll(chan *event.Event) error // poll alternative to watching :(
+	Prometheus() *prometheus.Prometheus
 }
 
 // Res is the minimum interface you need to implement to define a new resource.
@@ -193,6 +196,7 @@ type BaseRes struct {
 	events     chan *event.Event
 	converger  converger.Converger // converged tracking
 	cuid       converger.ConvergerUID
+	prometheus *prometheus.Prometheus
 	prefix     string // base prefix for this resource
 	debug      bool
 	state      ResState
@@ -348,6 +352,7 @@ func (obj *BaseRes) Events() chan *event.Event {
 // AssociateData associates some data with the object in question.
 func (obj *BaseRes) AssociateData(data *Data) {
 	obj.converger = data.Converger
+	obj.prometheus = data.Prometheus
 	obj.prefix = data.Prefix
 	obj.debug = data.Debug
 }
@@ -561,6 +566,11 @@ func (obj *BaseRes) Poll(processChan chan *event.Event) error {
 	}
 }
 
+// Prometheus returns the prometheus instance.
+func (obj *BaseRes) Prometheus() *prometheus.Prometheus {
+	return obj.prometheus
+}
+
 // ResToB64 encodes a resource to a base64 encoded string (after serialization)
 func ResToB64(res Res) (string, error) {
 	b := bytes.Buffer{}

test/shell/prometheus-3.sh

@@ -0,0 +1,20 @@
+#!/bin/bash -e
+
+# run empty graph, with prometheus support
+timeout --kill-after=20s 15s ./mgmt run --tmp-prefix --prometheus --yaml prometheus-3.yaml &
+pid=$!
+sleep 10s	# let it converge
+
+# For test debugging purpose
+curl 127.0.0.1:9233/metrics
+
+# Three CheckApply for a File ; with events
+curl 127.0.0.1:9233/metrics | grep '^mgmt_checkapply_total{apply="true",errorful="false",eventful="true",kind="File"} 3$'
+
+# One CheckApply for a File ; in noop mode.
+curl 127.0.0.1:9233/metrics | grep '^mgmt_checkapply_total{apply="false",errorful="false",eventful="true",kind="File"} 1$'
+
+
+killall -SIGINT mgmt	# send ^C to exit mgmt
+wait $pid	# get exit status
+exit $?

test/shell/prometheus-3.yaml

@@ -0,0 +1,26 @@
+---
+graph: mygraph
+resources:
+  file:
+  - name: file1
+    path: "/tmp/mgmt/f1"
+    content: |
+      i am f1
+    state: exists
+  - name: file2
+    path: "/tmp/mgmt/f2"
+    content: |
+      i am f2
+    state: exists
+  - name: file3
+    path: "/tmp/mgmt/f3"
+    content: |
+      i am f3
+    state: exists
+  - name: file4
+    path: "/tmp/mgmt/f4"
+    content: |
+      i am f4
+    state: exists
+    meta:
+      noop: true