Add support for adding aliases to index and shard stats (#563)

* Add support for adding aliases to index and shard stats

Optionally will include aliases in a label to index and shard stats

Signed-off-by: Steven Cipriano <cipriano@squareup.com>

* move aliases to separate informational metrics

Signed-off-by: Steven Cipriano <cipriano@squareup.com>

* address review

- switch boolean flag
- fix linting errors

Signed-off-by: Steven Cipriano <cipriano@squareup.com>

README.md

@@ -54,6 +54,7 @@ elasticsearch_exporter --help
 | es.indices              | 1.0.2                 | If true, query stats for all indices in the cluster. | false |
 | es.indices_settings     | 1.0.4rc1              | If true, query settings stats for all indices in the cluster. | false |
 | es.indices_mappings     | 1.2.0                 | If true, query stats for mappings of all indices of the cluster. | false |
+| es.aliases              | 1.0.4rc1              | If true, include informational aliases metrics. | true |
 | es.shards               | 1.0.3rc1              | If true, query stats for all indices in the cluster, including shard-level stats (implies `es.indices=true`). | false |
 | es.snapshots            | 1.0.4rc1              | If true, query stats for the cluster snapshots. | false |
 | es.slm                  |                       | If true, query stats for SLM. | false |

collector/indices.go

@@ -16,16 +16,16 @@ package collector
 import (
 	"encoding/json"
 	"fmt"
+	"github.com/go-kit/log"
+	"github.com/go-kit/log/level"
+	"github.com/prometheus-community/elasticsearch_exporter/pkg/clusterinfo"
+	"github.com/prometheus/client_golang/prometheus"
 	"io/ioutil"
 	"net/http"
 	"net/url"
 	"path"
+	"sort"
 	"strconv"
-
-	"github.com/go-kit/log"
-	"github.com/go-kit/log/level"
-	"github.com/prometheus-community/elasticsearch_exporter/pkg/clusterinfo"
-	"github.com/prometheus/client_golang/prometheus"
 )
 
 type labels struct {
@@ -47,12 +47,20 @@ type shardMetric struct {
 	Labels labels
 }
 
+type aliasMetric struct {
+	Type   prometheus.ValueType
+	Desc   *prometheus.Desc
+	Value  func() float64
+	Labels labels
+}
+
 // Indices information struct
 type Indices struct {
 	logger          log.Logger
 	client          *http.Client
 	url             *url.URL
 	shards          bool
+	aliases         bool
 	clusterInfoCh   chan *clusterinfo.Response
 	lastClusterInfo *clusterinfo.Response
 
@@ -62,10 +70,11 @@ type Indices struct {
 
 	indexMetrics []*indexMetric
 	shardMetrics []*shardMetric
+	aliasMetrics []*aliasMetric
 }
 
 // NewIndices defines Indices Prometheus metrics
-func NewIndices(logger log.Logger, client *http.Client, url *url.URL, shards bool) *Indices {
+func NewIndices(logger log.Logger, client *http.Client, url *url.URL, shards bool, includeAliases bool) *Indices {
 
 	indexLabels := labels{
 		keys: func(...string) []string {
@@ -95,11 +104,26 @@ func NewIndices(logger log.Logger, client *http.Client, url *url.URL, shards boo
 		},
 	}
 
+	aliasLabels := labels{
+		keys: func(...string) []string {
+			return []string{"index", "alias", "cluster"}
+		},
+		values: func(lastClusterinfo *clusterinfo.Response, s ...string) []string {
+			if lastClusterinfo != nil {
+				return append(s, lastClusterinfo.ClusterName)
+			}
+			// this shouldn't happen, as the clusterinfo Retriever has a blocking
+			// Run method. It blocks until the first clusterinfo call has succeeded
+			return append(s, "unknown_cluster")
+		},
+	}
+
 	indices := &Indices{
 		logger:        logger,
 		client:        client,
 		url:           url,
 		shards:        shards,
+		aliases:       includeAliases,
 		clusterInfoCh: make(chan *clusterinfo.Response),
 		lastClusterInfo: &clusterinfo.Response{
 			ClusterName: "unknown_cluster",
@@ -1022,6 +1046,21 @@ func NewIndices(logger log.Logger, client *http.Client, url *url.URL, shards boo
 				Labels: shardLabels,
 			},
 		},
+
+		aliasMetrics: []*aliasMetric{
+			{
+				Type: prometheus.GaugeValue,
+				Desc: prometheus.NewDesc(
+					prometheus.BuildFQName(namespace, "indices", "aliases"),
+					"Record aliases associated with an index",
+					aliasLabels.keys(), nil,
+				),
+				Value: func() float64 {
+					return float64(1)
+				},
+				Labels: aliasLabels,
+			},
+		},
 	}
 
 	// start go routine to fetch clusterinfo updates and save them to lastClusterinfo
@@ -1070,9 +1109,63 @@ func (i *Indices) fetchAndDecodeIndexStats() (indexStatsResponse, error) {
 		u.RawQuery = "ignore_unavailable=true"
 	}
 
+	bts, err := i.queryURL(&u)
+	if err != nil {
+		return isr, err
+	}
+
+	if err := json.Unmarshal(bts, &isr); err != nil {
+		i.jsonParseFailures.Inc()
+		return isr, err
+	}
+
+	if i.aliases {
+		isr.Aliases = map[string][]string{}
+		asr, err := i.fetchAndDecodeAliases()
+		if err != nil {
+			_ = level.Error(i.logger).Log("err", err.Error())
+			return isr, err
+		}
+
+		for indexName, aliases := range asr {
+			var aliasList []string
+			for aliasName := range aliases.Aliases {
+				aliasList = append(aliasList, aliasName)
+			}
+
+			if len(aliasList) > 0 {
+				sort.Strings(aliasList)
+				isr.Aliases[indexName] = aliasList
+			}
+		}
+	}
+
+	return isr, nil
+}
+
+func (i *Indices) fetchAndDecodeAliases() (aliasesResponse, error) {
+	var asr aliasesResponse
+
+	u := *i.url
+	u.Path = path.Join(u.Path, "/_alias")
+
+	bts, err := i.queryURL(&u)
+	if err != nil {
+		return asr, err
+	}
+
+	if err := json.Unmarshal(bts, &asr); err != nil {
+		i.jsonParseFailures.Inc()
+		return asr, err
+	}
+
+	return asr, nil
+}
+
+func (i *Indices) queryURL(u *url.URL) ([]byte, error) {
 	res, err := i.client.Get(u.String())
 	if err != nil {
-		return isr, fmt.Errorf("failed to get index stats from %s://%s:%s%s: %s",
+		return []byte{}, fmt.Errorf("failed to get resource from %s://%s:%s%s: %s",
 			u.Scheme, u.Hostname(), u.Port(), u.Path, err)
 	}
 
@@ -1087,21 +1180,15 @@ func (i *Indices) fetchAndDecodeIndexStats() (indexStatsResponse, error) {
 	}()
 
 	if res.StatusCode != http.StatusOK {
-		return isr, fmt.Errorf("HTTP Request failed with code %d", res.StatusCode)
+		return []byte{}, fmt.Errorf("HTTP Request failed with code %d", res.StatusCode)
 	}
 
 	bts, err := ioutil.ReadAll(res.Body)
 	if err != nil {
-		i.jsonParseFailures.Inc()
-		return isr, err
-	}
-
-	if err := json.Unmarshal(bts, &isr); err != nil {
-		i.jsonParseFailures.Inc()
-		return isr, err
+		return []byte{}, err
 	}
 
-	return isr, nil
+	return bts, nil
 }
 
 // Collect gets Indices metric values
@@ -1125,6 +1212,24 @@ func (i *Indices) Collect(ch chan<- prometheus.Metric) {
 	}
 	i.up.Set(1)
 
+	// Alias stats
+	if i.aliases {
+		for _, metric := range i.aliasMetrics {
+			for indexName, aliases := range indexStatsResp.Aliases {
+				for _, alias := range aliases {
+					labelValues := metric.Labels.values(i.lastClusterInfo, indexName, alias)
+
+					ch <- prometheus.MustNewConstMetric(
+						metric.Desc,
+						metric.Type,
+						metric.Value(),
+						labelValues...,
+					)
+				}
+			}
+		}
+	}
+
 	// Index stats
 	for indexName, indexStats := range indexStatsResp.Indices {
 		for _, metric := range i.indexMetrics {

collector/indices_response.go

@@ -18,6 +18,15 @@ type indexStatsResponse struct {
 	Shards  IndexStatsShardsResponse           `json:"_shards"`
 	All     IndexStatsIndexResponse            `json:"_all"`
 	Indices map[string]IndexStatsIndexResponse `json:"indices"`
+	Aliases map[string][]string
+}
+
+// aliasesResponse is a representation of a Elasticsearch Alias Query
+type aliasesResponse map[string]aliasMapping
+
+// aliasMapping is a mapping of index names to a map of associated alias names where the alias names are keys
+type aliasMapping struct {
+	Aliases map[string]map[string]interface{} `json:"aliases"`
 }
 
 // IndexStatsShardsResponse defines index stats shards information structure