feat: add settings for go sql.DB settings

plugins/outputs/sql/README.md

@@ -114,6 +114,20 @@ convert settings.
   ## the unsigned option. This is useful for a database like ClickHouse where
   ## the unsigned value should use a value like "uint64".
   # conversion_style = "unsigned_suffix"
+
+  ## Maximum amount of time a connection may be idle. "0s" means connections are
+  ## never closed due to idle time.
+  # connection_max_idle_time = "0s"
+
+  ## Maximum amount of time a connection may be reused. "0s" means connections
+  ## are never closed due to age.
+  # connection_max_lifetime = "0s"
+
+  ## Maximum number of connections in the idle connection pool. 0 means unlimited.
+  # connection_max_idle = 2
+
+  ## Maximum number of open connections to the database. 0 means unlimited.
+  # connection_max_open = 0
 ```
 
 ## Driver-specific information

plugins/outputs/sql/sample.conf

@@ -51,3 +51,17 @@
   ## the unsigned option. This is useful for a database like ClickHouse where
   ## the unsigned value should use a value like "uint64".
   # conversion_style = "unsigned_suffix"
+
+  ## Maximum amount of time a connection may be idle. "0s" means connections are
+  ## never closed due to idle time.
+  # connection_max_idle_time = "0s"
+
+  ## Maximum amount of time a connection may be reused. "0s" means connections
+  ## are never closed due to age.
+  # connection_max_lifetime = "0s"
+
+  ## Maximum number of connections in the idle connection pool. 0 means unlimited.
+  # connection_max_idle = 2
+
+  ## Maximum number of open connections to the database. 0 means unlimited.
+  # connection_max_open = 0

plugins/outputs/sql/sql.go

@@ -6,6 +6,7 @@ import (
 	_ "embed"
 	"fmt"
 	"strings"
+	"time"
 
 	//Register sql drivers
 	_ "github.com/ClickHouse/clickhouse-go" // clickhouse
@@ -34,13 +35,17 @@ type ConvertStruct struct {
 }
 
 type SQL struct {
-	Driver              string
-	DataSourceName      string
-	TimestampColumn     string
-	TableTemplate       string
-	TableExistsTemplate string
-	InitSQL             string `toml:"init_sql"`
-	Convert             ConvertStruct
+	Driver                string
+	DataSourceName        string
+	TimestampColumn       string
+	TableTemplate         string
+	TableExistsTemplate   string
+	InitSQL               string `toml:"init_sql"`
+	Convert               ConvertStruct
+	ConnectionMaxIdleTime time.Duration
+	ConnectionMaxLifetime time.Duration
+	ConnectionMaxIdle     int
+	ConnectionMaxOpen     int
 
 	db     *gosql.DB
 	Log    telegraf.Logger `toml:"-"`
@@ -62,6 +67,11 @@ func (p *SQL) Connect() error {
 		return err
 	}
 
+	db.SetConnMaxIdleTime(p.ConnectionMaxIdleTime)
+	db.SetConnMaxLifetime(p.ConnectionMaxLifetime)
+	db.SetMaxIdleConns(p.ConnectionMaxIdle)
+	db.SetMaxOpenConns(p.ConnectionMaxOpen)
+
 	if p.InitSQL != "" {
 		_, err = db.Exec(p.InitSQL)
 		if err != nil {
@@ -277,5 +287,11 @@ func newSQL() *SQL {
 			Bool:            "BOOL",
 			ConversionStyle: "unsigned_suffix",
 		},
+		// Defaults for the connection settings (ConnectionMaxIdleTime,
+		// ConnectionMaxLifetime, ConnectionMaxIdle, and ConnectionMaxOpen)
+		// mirror the golang defaults. As of go 1.18 all of them default to 0
+		// except max idle connections which is 2. See
+		// https://pkg.go.dev/database/sql#DB.SetMaxIdleConns
+		ConnectionMaxIdle: 2,
 	}
 }