prometheus: Add detailed metrics

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

prometheus/prometheus.go

@@ -20,17 +20,33 @@
 package prometheus
 
 import (
+	"errors"
 	"net/http"
 	"strconv"
+	"sync"
 
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/promhttp"
+
+	errwrap "github.com/pkg/errors"
 )
 
 // DefaultPrometheusListen is registered in
 // https://github.com/prometheus/prometheus/wiki/Default-port-allocations
 const DefaultPrometheusListen = "127.0.0.1:9233"
 
+// ResState represents the status of a resource.
+type ResState int
+
+const (
+	// ResStateOK represents a working resource
+	ResStateOK ResState = iota
+	// ResStateSoftFail represents a resource in soft fail (will be retried)
+	ResStateSoftFail
+	// ResStateHardFail represents a resource in hard fail (will NOT be retried)
+	ResStateHardFail
+)
+
 // Prometheus is the struct that contains information about the
 // prometheus instance. Run Init() on it.
 type Prometheus struct {
@@ -38,7 +54,18 @@ type Prometheus struct {
 
 	checkApplyTotal        *prometheus.CounterVec // total of CheckApplies that have been triggered
 	pgraphStartTimeSeconds prometheus.Gauge       // process start time in seconds since unix epoch
+	managedResources       *prometheus.GaugeVec   // Resources we manage now
+	failedResourcesTotal   *prometheus.CounterVec // Total of failures since mgmt has started
+	failedResources        *prometheus.GaugeVec   // Number of current resources
 
+	resourcesState map[string]resStateWithKind // Maps the resources with their current kind/state
+	mutex          *sync.Mutex                 // Mutex used to update resourcesState
+}
+
+// resStateWithKind is used to count the failures by kind
+type resStateWithKind struct {
+	state ResState
+	kind  string
 }
 
 // Init some parameters - currently the Listen address.
@@ -46,6 +73,10 @@ func (obj *Prometheus) Init() error {
 	if len(obj.Listen) == 0 {
 		obj.Listen = DefaultPrometheusListen
 	}
+
+	obj.mutex = &sync.Mutex{}
+	obj.resourcesState = make(map[string]resStateWithKind)
+
 	obj.checkApplyTotal = prometheus.NewCounterVec(
 		prometheus.CounterOpts{
 			Name: "mgmt_checkapply_total",
@@ -68,6 +99,38 @@ func (obj *Prometheus) Init() error {
 	)
 	prometheus.MustRegister(obj.pgraphStartTimeSeconds)
 
+	obj.managedResources = prometheus.NewGaugeVec(
+		prometheus.GaugeOpts{
+			Name: "mgmt_resources",
+			Help: "Number of managed resources.",
+		},
+		// kind: resource type: Svc, File, ...
+		[]string{"kind"},
+	)
+	prometheus.MustRegister(obj.managedResources)
+
+	obj.failedResourcesTotal = prometheus.NewCounterVec(
+		prometheus.CounterOpts{
+			Name: "mgmt_failures_total",
+			Help: "Total of failed resources.",
+		},
+		// kind: resource type: Svc, File, ...
+		// failure: soft or hard
+		[]string{"kind", "failure"},
+	)
+	prometheus.MustRegister(obj.failedResourcesTotal)
+
+	obj.failedResources = prometheus.NewGaugeVec(
+		prometheus.GaugeOpts{
+			Name: "mgmt_failures",
+			Help: "Number of failing resources.",
+		},
+		// kind: resource type: Svc, File, ...
+		// failure: soft or hard
+		[]string{"kind", "failure"},
+	)
+	prometheus.MustRegister(obj.failedResources)
+
 	return nil
 }
 
@@ -107,3 +170,94 @@ func (obj *Prometheus) UpdatePgraphStartTime() error {
 	obj.pgraphStartTimeSeconds.SetToCurrentTime()
 	return nil
 }
+
+// AddManagedResource increments the Managed Resource counter and updates the resource status.
+func (obj *Prometheus) AddManagedResource(resUUID string, rtype string) error {
+	if obj == nil {
+		return nil // happens when mgmt is launched without --prometheus
+	}
+	obj.managedResources.With(prometheus.Labels{"kind": rtype}).Inc()
+	if err := obj.UpdateState(resUUID, rtype, ResStateOK); err != nil {
+		return errwrap.Wrapf(err, "can't update the resource status in the map")
+	}
+	return nil
+}
+
+// RemoveManagedResource decrements the Managed Resource counter and updates the resource status.
+func (obj *Prometheus) RemoveManagedResource(resUUID string, rtype string) error {
+	if obj == nil {
+		return nil // happens when mgmt is launched without --prometheus
+	}
+	obj.managedResources.With(prometheus.Labels{"kind": rtype}).Dec()
+	if err := obj.deleteState(resUUID); err != nil {
+		return errwrap.Wrapf(err, "can't remove the resource status from the map")
+	}
+	return nil
+}
+
+// deleteState removes the resources for the state map and re-populates the failing gauge.
+func (obj *Prometheus) deleteState(resUUID string) error {
+	if obj == nil {
+		return nil // happens when mgmt is launched without --prometheus
+	}
+	obj.mutex.Lock()
+	delete(obj.resourcesState, resUUID)
+	obj.mutex.Unlock()
+	if err := obj.updateFailingGauge(); err != nil {
+		return errwrap.Wrapf(err, "can't update the failing gauge")
+	}
+	return nil
+}
+
+// UpdateState updates the state of the resources in our internal state map
+// then triggers a refresh of the failing gauge.
+func (obj *Prometheus) UpdateState(resUUID string, rtype string, newState ResState) error {
+	defer obj.updateFailingGauge()
+	if obj == nil {
+		return nil // happens when mgmt is launched without --prometheus
+	}
+	obj.mutex.Lock()
+	obj.resourcesState[resUUID] = resStateWithKind{state: newState, kind: rtype}
+	obj.mutex.Unlock()
+	if newState != ResStateOK {
+		var strState string
+		if newState == ResStateSoftFail {
+			strState = "soft"
+		} else if newState == ResStateHardFail {
+			strState = "hard"
+		} else {
+			return errors.New("state should be soft or hard failure")
+		}
+		obj.failedResourcesTotal.With(prometheus.Labels{"kind": rtype, "failure": strState}).Inc()
+	}
+	return nil
+}
+
+// updateFailingGauge refreshes the failing gauge by parsking the internal
+// state map.
+func (obj *Prometheus) updateFailingGauge() error {
+	if obj == nil {
+		return nil // happens when mgmt is launched without --prometheus
+	}
+	var softFails, hardFails map[string]float64
+	softFails = make(map[string]float64)
+	hardFails = make(map[string]float64)
+	for _, v := range obj.resourcesState {
+		if v.state == ResStateSoftFail {
+			softFails[v.kind]++
+		} else if v.state == ResStateHardFail {
+			hardFails[v.kind]++
+		}
+	}
+	// TODO: we might want to Zero the metrics we are not using
+	// because in prometheus design the metrics keep living for some time
+	// even after they are removed.
+	obj.failedResources.Reset()
+	for k, v := range softFails {
+		obj.failedResources.With(prometheus.Labels{"kind": k, "failure": "soft"}).Set(v)
+	}
+	for k, v := range hardFails {
+		obj.failedResources.With(prometheus.Labels{"kind": k, "failure": "hard"}).Set(v)
+	}
+	return nil
+}