feat: Add caching to internet_speed

plugins/inputs/internet_speed/README.md

@@ -8,8 +8,13 @@ The `Internet Speed Monitor` collects data about the internet speed on the syste
 # Monitors internet speed in the network
 [[inputs.internet_speed]]
   ## Sets if runs file download test
-  ## Default: false
-  enable_file_download = false
+  # enable_file_download = false
+
+  ## Time to sleep before running the speed test
+  # offset = "0s"
+
+  ## Caches the closest server location
+  # cache = false
 ```
 
 ## Metrics

plugins/inputs/internet_speed/internet_speed.go

@@ -12,13 +12,17 @@ import (
 // InternetSpeed is used to store configuration values.
 type InternetSpeed struct {
 	EnableFileDownload bool            `toml:"enable_file_download"`
+	Cache              bool            `toml:"cache"`
 	Log                telegraf.Logger `toml:"-"`
+	serverCache        *speedtest.Server
 }
 
 const sampleConfig = `
   ## Sets if runs file download test
-  ## Default: false  
-  enable_file_download = false
+  # enable_file_download = false
+
+  ## Caches the closest server location
+  # cache = false
 `
 
 // Description returns information about the plugin.
@@ -34,22 +38,31 @@ func (is *InternetSpeed) SampleConfig() string {
 const measurement = "internet_speed"
 
 func (is *InternetSpeed) Gather(acc telegraf.Accumulator) error {
-	user, err := speedtest.FetchUserInfo()
-	if err != nil {
-		return fmt.Errorf("fetching user info failed: %v", err)
-	}
-	serverList, err := speedtest.FetchServerList(user)
-	if err != nil {
-		return fmt.Errorf("fetching server list failed: %v", err)
-	}
 
-	if len(serverList.Servers) < 1 {
-		return fmt.Errorf("no servers found")
+	// Get closest server
+	s := is.serverCache
+	if s == nil {
+		user, err := speedtest.FetchUserInfo()
+		if err != nil {
+			return fmt.Errorf("fetching user info failed: %v", err)
+		}
+		serverList, err := speedtest.FetchServerList(user)
+		if err != nil {
+			return fmt.Errorf("fetching server list failed: %v", err)
+		}
+		if len(serverList.Servers) < 1 {
+			return fmt.Errorf("no servers found")
+		}
+		s = serverList.Servers[0]
+		is.Log.Debugf("Found server: %v", s)
+		if is.Cache {
+			is.serverCache = s
+		}
 	}
-	s := serverList.Servers[0]
+
 	is.Log.Debug("Starting Speed Test")
 	is.Log.Debug("Running Ping...")
-	err = s.PingTest()
+	err := s.PingTest()
 	if err != nil {
 		return fmt.Errorf("ping test failed: %v", err)
 	}
@@ -76,6 +89,7 @@ func (is *InternetSpeed) Gather(acc telegraf.Accumulator) error {
 	acc.AddFields(measurement, fields, tags)
 	return nil
 }
+
 func init() {
 	inputs.Add("internet_speed", func() telegraf.Input {
 		return &InternetSpeed{}