fix(mongodb): change command based on server version (#9674)

plugins/inputs/mongodb/README.md

@@ -1,5 +1,7 @@
 # MongoDB Input Plugin
 
+All MongoDB server versions from 2.6 and higher are supported.
+
 ### Configuration:
 
 ```toml

plugins/inputs/mongodb/mongodb_server.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"fmt"
 	"go.mongodb.org/mongo-driver/bson/primitive"
+	"strconv"
 	"strings"
 	"time"
 
@@ -126,11 +127,29 @@ func (s *Server) gatherClusterStatus() (*ClusterStatus, error) {
 	}, nil
 }
 
-func (s *Server) gatherShardConnPoolStats() (*ShardStats, error) {
+func poolStatsCommand(version string) (string, error) {
+	majorPart := string(version[0])
+	major, err := strconv.ParseInt(majorPart, 10, 64)
+	if err != nil {
+		return "", err
+	}
+
+	if major == 5 {
+		return "connPoolStats", nil
+	}
+	return "shardConnPoolStats", nil
+}
+
+func (s *Server) gatherShardConnPoolStats(version string) (*ShardStats, error) {
+	command, err := poolStatsCommand(version)
+	if err != nil {
+		return nil, err
+	}
+
 	shardStats := &ShardStats{}
-	err := s.runCommand("admin", bson.D{
+	err = s.runCommand("admin", bson.D{
 		{
-			Key:   "shardConnPoolStats",
+			Key:   command,
 			Value: 1,
 		},
 	}, &shardStats)
@@ -272,7 +291,7 @@ func (s *Server) gatherData(acc telegraf.Accumulator, gatherClusterStatus bool,
 		clusterStatus = status
 	}
 
-	shardStats, err := s.gatherShardConnPoolStats()
+	shardStats, err := s.gatherShardConnPoolStats(serverStatus.Version)
 	if err != nil {
 		s.authLog(fmt.Errorf("unable to gather shard connection pool stats: %s", err.Error()))
 	}

plugins/inputs/mongodb/mongodb_server_test.go

@@ -40,3 +40,45 @@ func TestAddDefaultStats(t *testing.T) {
 		assert.True(t, acc.HasInt64Field("mongodb", key))
 	}
 }
+
+func TestPoolStatsVersionCompatibility(t *testing.T) {
+	tests := []struct {
+		name            string
+		version         string
+		expectedCommand string
+		err             bool
+	}{
+		{
+			name:            "mongodb v3",
+			version:         "3.0.0",
+			expectedCommand: "shardConnPoolStats",
+		},
+		{
+			name:            "mongodb v4",
+			version:         "4.0.0",
+			expectedCommand: "shardConnPoolStats",
+		},
+		{
+			name:            "mongodb v5",
+			version:         "5.0.0",
+			expectedCommand: "connPoolStats",
+		},
+		{
+			name:    "invalid version",
+			version: "v4",
+			err:     true,
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			command, err := poolStatsCommand(test.version)
+			require.Equal(t, test.expectedCommand, command)
+			if test.err {
+				require.Error(t, err)
+			} else {
+				require.NoError(t, err)
+			}
+		})
+	}
+}