Add keep alive support to the TCP mode of statsd (#3781)

etc/telegraf.conf

@@ -3045,6 +3045,13 @@
 #
 #   ## MaxTCPConnection - applicable when protocol is set to tcp (default=250)
 #   max_tcp_connections = 250
+#   ## Enable TCP keep alive probes (default=false)
+#   tcp_keep_alive = false
+#
+#   ## Specifies the keep-alive period for an active network connection.
+#   ## Only applies to TCP sockets and will be ignored if tcp_keep_alive is false.
+#   ## Defaults to the OS configuration.
+#   # tcp_keep_alive_period = "2h"
 #
 #   ## Address and port to host UDP listener on
 #   service_address = ":8125"

plugins/inputs/statsd/README.md

@@ -10,6 +10,14 @@
 
   ## MaxTCPConnection - applicable when protocol is set to tcp (default=250)
   max_tcp_connections = 250
+  
+  ## Enable TCP keep alive probes (default=false)
+  tcp_keep_alive = false
+
+  ## Specifies the keep-alive period for an active network connection.
+  ## Only applies to TCP sockets and will be ignored if tcp_keep_alive is false.
+  ## Defaults to the OS configuration.
+  # tcp_keep_alive_period = "2h"
 
   ## Address and port to host UDP listener on
   service_address = ":8125"
@@ -157,6 +165,8 @@ metric type:
 - **protocol** string: Protocol used in listener - tcp or udp options
 - **max_tcp_connections** []int: Maximum number of concurrent TCP connections
 to allow. Used when protocol is set to tcp.
+- **tcp_keep_alive** boolean: Enable TCP keep alive probes
+- **tcp_keep_alive_period** internal.Duration: Specifies the keep-alive period for an active network connection
 - **service_address** string: Address to listen for statsd UDP packets on
 - **delete_gauges** boolean: Delete gauges on every collection interval
 - **delete_counters** boolean: Delete counters on every collection interval

plugins/inputs/statsd/statsd.go

@@ -113,6 +113,9 @@ type Statsd struct {
 
 	MaxTCPConnections int `toml:"max_tcp_connections"`
 
+	TCPKeepAlive       bool               `toml:"tcp_keep_alive"`
+	TCPKeepAlivePeriod *internal.Duration `toml:"tcp_keep_alive_period"`
+
 	graphiteParser *graphite.GraphiteParser
 
 	acc telegraf.Accumulator
@@ -177,6 +180,14 @@ const sampleConfig = `
   ## MaxTCPConnection - applicable when protocol is set to tcp (default=250)
   max_tcp_connections = 250
 
+  ## Enable TCP keep alive probes (default=false)
+  tcp_keep_alive = false
+
+  ## Specifies the keep-alive period for an active network connection.
+  ## Only applies to TCP sockets and will be ignored if tcp_keep_alive is false.
+  ## Defaults to the OS configuration.
+  # tcp_keep_alive_period = "2h"
+
   ## Address and port to host UDP listener on
   service_address = ":8125"
 
@@ -361,6 +372,18 @@ func (s *Statsd) tcpListen() error {
 				return err
 			}
 
+			if s.TCPKeepAlive {
+				if err = conn.SetKeepAlive(true); err != nil {
+					return err
+				}
+
+				if s.TCPKeepAlivePeriod != nil {
+					if err = conn.SetKeepAlivePeriod(s.TCPKeepAlivePeriod.Duration); err != nil {
+						return err
+					}
+				}
+			}
+
 			select {
 			case <-s.accept:
 				// not over connection limit, handle the connection properly.
@@ -863,6 +886,7 @@ func init() {
 			Protocol:               defaultProtocol,
 			ServiceAddress:         ":8125",
 			MaxTCPConnections:      250,
+			TCPKeepAlive:           false,
 			MetricSeparator:        "_",
 			AllowedPendingMessages: defaultAllowPendingMessage,
 			DeleteCounters:         true,