Fix cluster settings collection when max_shards_per_node is manually set (prometheus-community#603)

Signed-off-by: akazs <[email protected]>

Author: akazs

collector/cluster_settings.go

@@ -174,8 +174,10 @@ func (cs *ClusterSettings) Collect(ch chan<- prometheus.Metric) {
 
 	cs.shardAllocationEnabled.Set(float64(shardAllocationMap[csr.Cluster.Routing.Allocation.Enabled]))
 
-	maxShardsPerNode, err := strconv.ParseInt(csr.Cluster.MaxShardsPerNode, 10, 64)
-	if err == nil {
-		cs.maxShardsPerNode.Set(float64(maxShardsPerNode))
+	if maxShardsPerNodeString, ok := csr.Cluster.MaxShardsPerNode.(string); ok {
+		maxShardsPerNode, err := strconv.ParseInt(maxShardsPerNodeString, 10, 64)
+		if err == nil {
+			cs.maxShardsPerNode.Set(float64(maxShardsPerNode))
+		}
 	}
 }

collector/cluster_settings_response.go

@@ -27,8 +27,9 @@ type ClusterSettingsResponse struct {
 
 // Cluster is a representation of a Elasticsearch Cluster Settings
 type Cluster struct {
-	Routing          Routing `json:"routing"`
-	MaxShardsPerNode string  `json:"max_shards_per_node"`
+	Routing Routing `json:"routing"`
+	// This can be either a JSON object (which does not contain the value we are interested in) or a string
+	MaxShardsPerNode interface{} `json:"max_shards_per_node"`
 }
 
 // Routing is a representation of a Elasticsearch Cluster shard routing configuration

collector/cluster_settings_test.go

@@ -53,18 +53,22 @@ func TestClusterSettingsStats(t *testing.T) {
 			if nsr.Cluster.Routing.Allocation.Enabled != "ALL" {
 				t.Errorf("Wrong setting for cluster routing allocation enabled")
 			}
-			if nsr.Cluster.MaxShardsPerNode != "" {
+			if nsr.Cluster.MaxShardsPerNode != nil {
 				t.Errorf("MaxShardsPerNode should be empty on older releases")
 			}
 		}
 	}
 }
 
 func TestClusterMaxShardsPerNode(t *testing.T) {
-	// Testcases created using:
+	// settings-7.3.0.json testcase created using:
 	//  docker run -d -p 9200:9200 elasticsearch:VERSION-alpine
 	//  curl http://localhost:9200/_cluster/settings/?include_defaults=true
-	files := []string{"../fixtures/settings-7.3.0.json"}
+	// settings-persistent-clustermaxshartspernode-7.17.json testcase created using:
+	//  docker run -d -p 9200:9200 elasticsearch:VERSION
+	//  curl -X PUT http://localhost:9200/_cluster/settings -H 'Content-Type: application/json' -d '{"persistent":{"cluster.max_shards_per_node":1000}}'
+	//  curl http://localhost:9200/_cluster/settings/?include_defaults=true
+	files := []string{"../fixtures/settings-7.3.0.json", "../fixtures/settings-persistent-clustermaxshartspernode-7.17.5.json"}
 	for _, filename := range files {
 		f, _ := os.Open(filename)
 		defer f.Close()