Add external labels to template expansion

This affects the expansion of templates in alert labels and
annotations and console templates.

Signed-off-by: Sylvain Rabot <sylvain@abstraction.fr>

cmd/prometheus/main.go

@@ -748,6 +748,12 @@ func reloadConfig(filename string, logger log.Logger, rls ...func(*config.Config
 		return errors.Errorf("one or more errors occurred while applying the new configuration (--config.file=%q)", filename)
 	}
 	promql.SetDefaultEvaluationInterval(time.Duration(conf.GlobalConfig.EvaluationInterval))
+
+	// Register conf as current config.
+	config.CurrentConfigMutex.Lock()
+	config.CurrentConfig = conf
+	config.CurrentConfigMutex.Unlock()
+
 	level.Info(logger).Log("msg", "Completed loading of configuration file", "filename", filename)
 	return nil
 }

config/config.go

@@ -20,6 +20,7 @@ import (
 	"path/filepath"
 	"regexp"
 	"strings"
+	"sync"
 	"time"
 
 	"github.com/pkg/errors"
@@ -68,6 +69,10 @@ func LoadFile(filename string) (*Config, error) {
 
 // The defaults applied before parsing the respective config sections.
 var (
+	// CurrentConfig is a pointer to the current configuration.
+	CurrentConfig      *Config
+	CurrentConfigMutex sync.RWMutex
+
 	// DefaultConfig is the default top-level configuration.
 	DefaultConfig = Config{
 		GlobalConfig: DefaultGlobalConfig,

docs/configuration/alerting_rules.md

@@ -43,7 +43,7 @@ The `annotations` clause specifies a set of informational labels that can be use
 #### Templating
 
 Label and annotation values can be templated using [console templates](https://prometheus.io/docs/visualization/consoles).
-The `$labels` variable holds the label key/value pairs of an alert instance
+The `$labels` & `$externalLabels` variables hold the label key/value pairs of an alert instance
 and `$value` holds the evaluated value of an alert instance.
 
     # To insert a firing element's label values:

pkg/rulefmt/rulefmt.go

@@ -155,7 +155,7 @@ func testTemplateParsing(rl *Rule) (errs []error) {
 	}
 
 	// Trying to parse templates.
-	tmplData := template.AlertTemplateData(make(map[string]string), 0)
+	tmplData := template.AlertTemplateData(make(map[string]string), make(map[string]string), 0)
 	defs := "{{$labels := .Labels}}{{$value := .Value}}"
 	parseTest := func(text string) error {
 		tmpl := template.NewTemplateExpander(

rules/alerting.go

@@ -28,6 +28,7 @@ import (
 	"github.com/go-kit/kit/log/level"
 	"github.com/pkg/errors"
 	"github.com/prometheus/common/model"
+	"github.com/prometheus/prometheus/config"
 
 	"github.com/prometheus/prometheus/pkg/labels"
 	"github.com/prometheus/prometheus/pkg/rulefmt"
@@ -79,8 +80,9 @@ func (s AlertState) String() string {
 type Alert struct {
 	State AlertState
 
-	Labels      labels.Labels
-	Annotations labels.Labels
+	Labels         labels.Labels
+	ExternalLabels labels.Labels
+	Annotations    labels.Labels
 
 	// The value at the last evaluation of the alerting expression.
 	Value float64
@@ -300,15 +302,27 @@ func (r *AlertingRule) Eval(ctx context.Context, ts time.Time, query QueryFunc,
 	var vec promql.Vector
 	for _, smpl := range res {
 		// Provide the alert information to the template.
-		l := make(map[string]string, len(smpl.Metric))
+		l := make(map[string]string)
 		for _, lbl := range smpl.Metric {
 			l[lbl.Name] = lbl.Value
 		}
 
-		tmplData := template.AlertTemplateData(l, smpl.V)
+		// Add external labels.
+		el := make(map[string]string)
+		if config.CurrentConfig != nil {
+			config.CurrentConfigMutex.RLock()
+			for eln, elv := range (*config.CurrentConfig).GlobalConfig.ExternalLabels {
+				el[string(eln)] = string(elv)
+			}
+			config.CurrentConfigMutex.RUnlock()
+		}
+
+		tmplData := template.AlertTemplateData(l, el, smpl.V)
 		// Inject some convenience variables that are easier to remember for users
 		// who are not used to Go's templating system.
-		defs := "{{$labels := .Labels}}{{$value := .Value}}"
+		defs := "{{$labels := .Labels}}"
+		defs += "{{$externalLabels := .ExternalLabels}}"
+		defs += "{{$value := .Value}}"
 
 		expand := func(text string) string {
 			tmpl := template.NewTemplateExpander(

template/template.go

@@ -28,9 +28,10 @@ import (
 	text_template "text/template"
 
 	"github.com/pkg/errors"
+
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/common/model"
-
+	"github.com/prometheus/prometheus/config"
 	"github.com/prometheus/prometheus/promql"
 	"github.com/prometheus/prometheus/util/strutil"
 )
@@ -133,6 +134,19 @@ func NewTemplateExpander(
 			"label": func(label string, s *sample) string {
 				return s.Labels[label]
 			},
+			"externalLabel": func(label string) string {
+				if config.CurrentConfig == nil {
+					return ""
+				}
+				config.CurrentConfigMutex.RLock()
+				defer config.CurrentConfigMutex.RUnlock()
+				for eln, elv := range (*config.CurrentConfig).GlobalConfig.ExternalLabels {
+					if label == string(eln) {
+						return string(elv)
+					}
+				}
+				return ""
+			},
 			"value": func(s *sample) float64 {
 				return s.Value
 			},
@@ -261,13 +275,15 @@ func NewTemplateExpander(
 }
 
 // AlertTemplateData returns the interface to be used in expanding the template.
-func AlertTemplateData(labels map[string]string, value float64) interface{} {
+func AlertTemplateData(labels map[string]string, externalLabels map[string]string, value float64) interface{} {
 	return struct {
-		Labels map[string]string
-		Value  float64
+		Labels         map[string]string
+		ExternalLabels map[string]string
+		Value          float64
 	}{
-		Labels: labels,
-		Value:  value,
+		Labels:         labels,
+		ExternalLabels: externalLabels,
+		Value:          value,
 	}
 }
 

web/web.go

@@ -541,19 +541,39 @@ func (h *Handler) consoles(w http.ResponseWriter, r *http.Request) {
 	for k, v := range rawParams {
 		params[k] = v[0]
 	}
+
+	// External labels
+	el := make(map[string]string)
+	if config.CurrentConfig != nil {
+		config.CurrentConfigMutex.RLock()
+		for eln, elv := range (*config.CurrentConfig).GlobalConfig.ExternalLabels {
+			el[string(eln)] = string(elv)
+		}
+		config.CurrentConfigMutex.RUnlock()
+	}
+
+	// Inject some convenience variables that are easier to remember for users
+	// who are not used to Go's templating system.
+	defs := "{{$rawParams := .RawParams }}"
+	defs += "{{$params := .Params}}"
+	defs += "{{$path := .Path}}"
+	defs += "{{$externalLabels := .ExternalLabels}}"
+
 	data := struct {
-		RawParams url.Values
-		Params    map[string]string
-		Path      string
+		RawParams      url.Values
+		Params         map[string]string
+		Path           string
+		ExternalLabels map[string]string
 	}{
-		RawParams: rawParams,
-		Params:    params,
-		Path:      strings.TrimLeft(name, "/"),
+		RawParams:      rawParams,
+		Params:         params,
+		Path:           strings.TrimLeft(name, "/"),
+		ExternalLabels: el,
 	}
 
 	tmpl := template.NewTemplateExpander(
 		h.context,
-		string(text),
+		defs+string(text),
 		"__console_"+name,
 		data,
 		h.now(),