Refactor cluster info collector

collector/cluster_info.go

@@ -0,0 +1,109 @@
+// Copyright 2022 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package collector
+
+import (
+	"context"
+	"encoding/json"
+	"io/ioutil"
+	"net/http"
+	"net/url"
+
+	"github.com/blang/semver"
+	"github.com/go-kit/log"
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+func init() {
+	registerCollector("cluster-info", defaultEnabled, NewClusterInfo)
+}
+
+type ClusterInfoCollector struct {
+	logger log.Logger
+	u      *url.URL
+	hc     *http.Client
+}
+
+func NewClusterInfo(logger log.Logger, u *url.URL, hc *http.Client) (Collector, error) {
+	return &ClusterInfoCollector{
+		logger: logger,
+		u:      u,
+		hc:     hc,
+	}, nil
+}
+
+var clusterInfoDesc = map[string]*prometheus.Desc{
+	"version": prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, "", "version"),
+		"Elasticsearch version information.",
+		[]string{
+			"cluster",
+			"cluster_uuid",
+			"build_date",
+			"build_hash",
+			"version",
+			"lucene_version",
+		},
+		nil,
+	),
+}
+
+// ClusterInfoResponse is the cluster info retrievable from the / endpoint
+type ClusterInfoResponse struct {
+	Name        string      `json:"name"`
+	ClusterName string      `json:"cluster_name"`
+	ClusterUUID string      `json:"cluster_uuid"`
+	Version     VersionInfo `json:"version"`
+	Tagline     string      `json:"tagline"`
+}
+
+// VersionInfo is the version info retrievable from the / endpoint, embedded in ClusterInfoResponse
+type VersionInfo struct {
+	Number        semver.Version `json:"number"`
+	BuildHash     string         `json:"build_hash"`
+	BuildDate     string         `json:"build_date"`
+	BuildSnapshot bool           `json:"build_snapshot"`
+	LuceneVersion semver.Version `json:"lucene_version"`
+}
+
+func (c *ClusterInfoCollector) Update(ctx context.Context, ch chan<- prometheus.Metric) error {
+	resp, err := c.hc.Get(c.u.String())
+	if err != nil {
+		return err
+	}
+	defer resp.Body.Close()
+	b, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		return err
+	}
+	var info ClusterInfoResponse
+	err = json.Unmarshal(b, &info)
+	if err != nil {
+		return err
+	}
+
+	ch <- prometheus.MustNewConstMetric(
+		clusterInfoDesc["version"],
+		prometheus.GaugeValue,
+		1,
+		info.ClusterName,
+		info.ClusterUUID,
+		info.Version.BuildDate,
+		info.Version.BuildHash,
+		info.Version.Number.String(),
+		info.Version.LuceneVersion.String(),
+	)
+
+	return nil
+}

collector/collector.go

@@ -16,6 +16,8 @@ package collector
 
 import (
 	"context"
+	"errors"
+	"fmt"
 	"net/http"
 	"net/url"
 	"sync"
@@ -24,10 +26,26 @@ import (
 	"github.com/go-kit/log"
 	"github.com/go-kit/log/level"
 	"github.com/prometheus/client_golang/prometheus"
+	"gopkg.in/alecthomas/kingpin.v2"
 )
 
-// Namespace defines the common namespace to be used by all metrics.
-const namespace = "elasticsearch"
+const (
+	// Namespace defines the common namespace to be used by all metrics.
+	namespace = "elasticsearch"
+
+	defaultEnabled = true
+	// defaultDisabled = false
+)
+
+type factoryFunc func(logger log.Logger, u *url.URL, hc *http.Client) (Collector, error)
+
+var (
+	factories              = make(map[string]factoryFunc)
+	initiatedCollectorsMtx = sync.Mutex{}
+	initiatedCollectors    = make(map[string]Collector)
+	collectorState         = make(map[string]*bool)
+	forcedCollectors       = map[string]bool{} // collectors which have been explicitly enabled or disabled
+)
 
 var (
 	scrapeDurationDesc = prometheus.NewDesc(
@@ -50,16 +68,92 @@ type Collector interface {
 	Update(context.Context, chan<- prometheus.Metric) error
 }
 
+func registerCollector(name string, isDefaultEnabled bool, createFunc factoryFunc) {
+	var helpDefaultState string
+	if isDefaultEnabled {
+		helpDefaultState = "enabled"
+	} else {
+		helpDefaultState = "disabled"
+	}
+
+	// Create flag for this collector
+	flagName := fmt.Sprintf("collector.%s", name)
+	flagHelp := fmt.Sprintf("Enable the %s collector (default: %s).", name, helpDefaultState)
+	defaultValue := fmt.Sprintf("%v", isDefaultEnabled)
+
+	flag := kingpin.Flag(flagName, flagHelp).Default(defaultValue).Action(collectorFlagAction(name)).Bool()
+	collectorState[name] = flag
+
+	// Register the create function for this collector
+	factories[name] = createFunc
+}
+
 type ElasticsearchCollector struct {
 	Collectors map[string]Collector
 	logger     log.Logger
+	esURL      *url.URL
+	httpClient *http.Client
 }
 
+type Option func(*ElasticsearchCollector) error
+
 // NewElasticsearchCollector creates a new ElasticsearchCollector
-func NewElasticsearchCollector(logger log.Logger, httpClient *http.Client, esURL *url.URL) (*ElasticsearchCollector, error) {
+func NewElasticsearchCollector(logger log.Logger, filters []string, options ...Option) (*ElasticsearchCollector, error) {
+	e := &ElasticsearchCollector{logger: logger}
+	// Apply options to customize the collector
+	for _, o := range options {
+		if err := o(e); err != nil {
+			return nil, err
+		}
+	}
+
+	f := make(map[string]bool)
+	for _, filter := range filters {
+		enabled, exist := collectorState[filter]
+		if !exist {
+			return nil, fmt.Errorf("missing collector: %s", filter)
+		}
+		if !*enabled {
+			return nil, fmt.Errorf("disabled collector: %s", filter)
+		}
+		f[filter] = true
+	}
 	collectors := make(map[string]Collector)
+	initiatedCollectorsMtx.Lock()
+	defer initiatedCollectorsMtx.Unlock()
+	for key, enabled := range collectorState {
+		if !*enabled || (len(f) > 0 && !f[key]) {
+			continue
+		}
+		if collector, ok := initiatedCollectors[key]; ok {
+			collectors[key] = collector
+		} else {
+			collector, err := factories[key](log.With(logger, "collector", key), e.esURL, e.httpClient)
+			if err != nil {
+				return nil, err
+			}
+			collectors[key] = collector
+			initiatedCollectors[key] = collector
+		}
+	}
+
+	e.Collectors = collectors
+
+	return e, nil
+}
 
-	return &ElasticsearchCollector{Collectors: collectors, logger: logger}, nil
+func WithElasticsearchURL(esURL *url.URL) Option {
+	return func(e *ElasticsearchCollector) error {
+		e.esURL = esURL
+		return nil
+	}
+}
+
+func WithHTTPClient(hc *http.Client) Option {
+	return func(e *ElasticsearchCollector) error {
+		e.httpClient = hc
+		return nil
+	}
 }
 
 // Describe implements the prometheus.Collector interface.
@@ -89,7 +183,11 @@ func execute(ctx context.Context, name string, c Collector, ch chan<- prometheus
 	var success float64
 
 	if err != nil {
-		_ = level.Error(logger).Log("msg", "collector failed", "name", name, "duration_seconds", duration.Seconds(), "err", err)
+		if IsNoDataError(err) {
+			_ = level.Debug(logger).Log("msg", "collector returned no data", "name", name, "duration_seconds", duration.Seconds(), "err", err)
+		} else {
+			_ = level.Error(logger).Log("msg", "collector failed", "name", name, "duration_seconds", duration.Seconds(), "err", err)
+		}
 		success = 0
 	} else {
 		_ = level.Debug(logger).Log("msg", "collector succeeded", "name", name, "duration_seconds", duration.Seconds())
@@ -98,3 +196,22 @@ func execute(ctx context.Context, name string, c Collector, ch chan<- prometheus
 	ch <- prometheus.MustNewConstMetric(scrapeDurationDesc, prometheus.GaugeValue, duration.Seconds(), name)
 	ch <- prometheus.MustNewConstMetric(scrapeSuccessDesc, prometheus.GaugeValue, success, name)
 }
+
+// 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
+	}
+}
+
+// ErrNoData indicates the collector found no data to collect, but had no other error.
+var ErrNoData = errors.New("collector returned no data")
+
+func IsNoDataError(err error) bool {
+	return err == ErrNoData
+}

main.go

@@ -157,6 +157,20 @@ func main() {
 	// version metric
 	prometheus.MustRegister(version.NewCollector(name))
 
+	// create the exporter
+	exporter, err := collector.NewElasticsearchCollector(
+		logger,
+		[]string{},
+		collector.WithElasticsearchURL(esURL),
+		collector.WithHTTPClient(httpClient),
+	)
+	if err != nil {
+		_ = level.Error(logger).Log("msg", "failed to create Elasticsearch collector", "err", err)
+		os.Exit(1)
+	}
+	prometheus.MustRegister(exporter)
+
+	// TODO(@sysadmind): Remove this when we have a better way to get the cluster name to down stream collectors.
 	// cluster info retriever
 	clusterInfoRetriever := clusterinfo.New(logger, httpClient, esURL, *esClusterInfoInterval)