fix invalid memory address, added collect.shardingstatus flag (#199)

* fix "panic: runtime error: invalid memory address or nil pointer dereference"

* replace spaces with tabs

* changelog, version

* recommendation: from collect.shardingstatus to suppress.collectshardingstatus

* add new flag to test help

CHANGELOG.md

@@ -7,6 +7,16 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## [0.11.2]
+### Added
+- [PMM-6361](https://jira.percona.com/browse/PMM-6361): New flag `--suppress.collectshardingstatus` can be used to disable the collection of Sharding Status. This flag is not set by default. 
+On a large scale cluster it could help you to disable the mongoS exporters induced load to config tables. [@vrazvan-adobe](https://github.com/vrazvan-adobe)
+
+### Fixed
+- [PMM-6361](https://jira.percona.com/browse/PMM-6361): `runtime error: invalid memory address or nil pointer dereference`, source="sharding_status.go:166" .
+When chunks collection is very big, the aggregate on it can take longer then default default 1000ms SocketTimeout. [@vrazvan-adobe](https://github.com/vrazvan-adobe)                                        
+
+
 ## [0.11.0]
 ### Changed
 - `go.mongodb.org/mongo-driver` was updated to `v1.3.2`.

VERSION

@@ -1 +1 @@
-0.10.0
+0.11.2

collector/mongodb_collector.go

@@ -40,6 +40,7 @@ type MongodbCollectorOpts struct {
 	CollectTopMetrics        bool
 	CollectIndexUsageStats   bool
 	CollectConnPoolStats     bool
+	SuppressCollectShardingStatus    bool
 }
 
 func (in *MongodbCollectorOpts) toSessionOps() *shared.MongoSessionOpts {
@@ -226,10 +227,12 @@ func (exporter *MongodbCollector) collectMongos(client *mongo.Client, ch chan<-
 		serverStatus.Export(ch)
 	}
 
-	log.Debug("Collecting Sharding Status")
-	shardingStatus := mongos.GetShardingStatus(client)
-	if shardingStatus != nil {
-		shardingStatus.Export(ch)
+	if !exporter.Opts.SuppressCollectShardingStatus  {
+		log.Debug("Collecting Sharding Status")
+		shardingStatus := mongos.GetShardingStatus(client)
+		if shardingStatus != nil {
+			shardingStatus.Export(ch)
+		}
 	}
 
 	if exporter.Opts.CollectDatabaseMetrics {

collector/mongos/sharding_status.go

@@ -163,12 +163,14 @@ func IsClusterBalanced(client *mongo.Client) float64 {
 	var minChunkCount float64 = -1
 	var maxChunkCount float64 = 0
 	shardChunkInfoAll := GetTotalChunksByShard(client)
-	for _, shard := range *shardChunkInfoAll {
-		if shard.Chunks > maxChunkCount {
-			maxChunkCount = shard.Chunks
-		}
-		if minChunkCount == -1 || shard.Chunks < minChunkCount {
-			minChunkCount = shard.Chunks
+	if shardChunkInfoAll != nil {
+		for _, shard := range *shardChunkInfoAll {
+			if shard.Chunks > maxChunkCount {
+				maxChunkCount = shard.Chunks
+			}
+			if minChunkCount == -1 || shard.Chunks < minChunkCount {
+				minChunkCount = shard.Chunks
+			}
 		}
 	}
 

mongodb_exporter.go

@@ -47,6 +47,7 @@ var (
 	collectTopF                  = kingpin.Flag("collect.topmetrics", "Enable collection of table top metrics").Bool()
 	collectIndexUsageF           = kingpin.Flag("collect.indexusage", "Enable collection of per index usage stats").Bool()
 	mongodbCollectConnPoolStatsF = kingpin.Flag("collect.connpoolstats", "Collect MongoDB connpoolstats").Bool()
+	suppressCollectShardingStatusF = kingpin.Flag("suppress.collectshardingstatus", "Suppress the collection of Sharding Status").Default("false").Bool()
 
 	uriF = kingpin.Flag("mongodb.uri", "MongoDB URI, format").
 		PlaceHolder("[mongodb://][user:pass@]host1[:port1][,host2[:port2],...][/database][?options]").
@@ -88,6 +89,7 @@ func main() {
 		CollectTopMetrics:        *collectTopF,
 		CollectIndexUsageStats:   *collectIndexUsageF,
 		CollectConnPoolStats:     *mongodbCollectConnPoolStatsF,
+		SuppressCollectShardingStatus:    *suppressCollectShardingStatusF,
 	})
 	prometheus.MustRegister(programCollector, mongodbCollector)
 

testdata/mongodb_exporter.testFlagHelp.golden

@@ -24,6 +24,8 @@ Flags:
       --collect.topmetrics     Enable collection of table top metrics
       --collect.indexusage     Enable collection of per index usage stats
       --collect.connpoolstats  Collect MongoDB connpoolstats
+      --suppress.collectshardingstatus  
+                               Suppress the collection of Sharding Status
       --mongodb.uri=[mongodb://][user:pass@]host1[:port1][,host2[:port2],...][/database][?options]  
                                MongoDB URI, format
       --test                   Check MongoDB connection, print buildInfo()