Add per-host shard metrics in mongodb input (#3819)

plugins/inputs/mongodb/mongostat.go

@@ -125,12 +125,27 @@ type WiredTiger struct {
 
 // ShardStats stores information from shardConnPoolStats.
 type ShardStats struct {
+	ShardStatsData `bson:",inline"`
+	Hosts          map[string]ShardHostStatsData `bson:"hosts"`
+}
+
+// ShardStatsData is the total Shard Stats from shardConnPoolStats database command.
+type ShardStatsData struct {
 	TotalInUse      int64 `bson:"totalInUse"`
 	TotalAvailable  int64 `bson:"totalAvailable"`
 	TotalCreated    int64 `bson:"totalCreated"`
 	TotalRefreshing int64 `bson:"totalRefreshing"`
 }
 
+// ShardHostStatsData is the host-specific stats
+// from shardConnPoolStats database command.
+type ShardHostStatsData struct {
+	InUse      int64 `bson:"inUse"`
+	Available  int64 `bson:"available"`
+	Created    int64 `bson:"created"`
+	Refreshing int64 `bson:"refreshing"`
+}
+
 type ConcurrentTransactions struct {
 	Write ConcurrentTransStats `bson:"write"`
 	Read  ConcurrentTransStats `bson:"read"`
@@ -469,6 +484,9 @@ type StatLine struct {
 
 	// Shard stats
 	TotalInUse, TotalAvailable, TotalCreated, TotalRefreshing int64
+
+	// Shard Hosts stats field
+	ShardHostStatsLines map[string]ShardHostStatLine
 }
 
 type DbStatLine struct {
@@ -484,6 +502,13 @@ type DbStatLine struct {
 	Ok          int64
 }
 
+type ShardHostStatLine struct {
+	InUse      int64
+	Available  int64
+	Created    int64
+	Refreshing int64
+}
+
 func parseLocks(stat ServerStatus) map[string]LockUsage {
 	returnVal := map[string]LockUsage{}
 	for namespace, lockInfo := range stat.Locks {
@@ -809,6 +834,17 @@ func NewStatLine(oldMongo, newMongo MongoStatus, key string, all bool, sampleSec
 	returnVal.TotalAvailable = newShardStats.TotalAvailable
 	returnVal.TotalCreated = newShardStats.TotalCreated
 	returnVal.TotalRefreshing = newShardStats.TotalRefreshing
+	returnVal.ShardHostStatsLines = map[string]ShardHostStatLine{}
+	for host, stats := range newShardStats.Hosts {
+		shardStatLine := &ShardHostStatLine{
+			InUse:      stats.InUse,
+			Available:  stats.Available,
+			Created:    stats.Created,
+			Refreshing: stats.Refreshing,
+		}
+
+		returnVal.ShardHostStatsLines[host] = *shardStatLine
+	}
 
 	return returnVal
 }