Logstation now has two tailing methods: filesystem or polling

config.go

@@ -20,6 +20,8 @@ func HandleConfigFile(configFilePath string) {
 	viper.SetDefault("logs", []string{`test\logfile.log`, `test\logfile2.log`})
 	viper.SetDefault("server_settings.webserveraddress", "0.0.0.0")
 	viper.SetDefault("server_settings.disablecors", false)
+	viper.SetDefault("tailingMethod", "filesystem")
+	viper.SetDefault("pollingTimeMS", 10)
 
 	viper.SetConfigFile(configFilePath)
 	if err := viper.ReadInConfig(); err != nil {

logstation.default.conf

@@ -19,27 +19,27 @@ logs = [
 ]
 # Unix example of setting up logs
 #logs = [
-#    '/home/jdrews/git/logstation/logfile.log',
-#    '/home/jdrews/git/logstation/*.log'
+#   '/home/jdrews/git/logstation/logfile.log',
+#   '/home/jdrews/git/logstation/*.log'
 #]
 
 # Unique name for logstation instance
-#    This name will be prepended to the browser tab
-#    Can be useful when connecting to multiple logstations
+#   This name will be prepended to the browser tab
+#   Can be useful when connecting to multiple logstations
 logStationName = "logstation"
 
 # Setup your syntax highlighting below
-#     matching gives priority to the top most
-#     if the regular experssion passes, the entire log line will be colored
+#   matching gives priority to the top most
+#   if the regular experssion passes, the entire log line will be colored
 #
-#     "color" can be any of of the following
-#        red, green, yellow, blue, magenta, cyan
-#        hired, higreen, hiyellow, hiblue, himagenta, hicyan
-#        NOTE: these are ANSI colors.
-#           The "hi" colors above are recommended as they show up much better on black backgrounds
+#   "color" can be any of of the following
+#       red, green, yellow, blue, magenta, cyan
+#       hired, higreen, hiyellow, hiblue, himagenta, hicyan
+#       NOTE: these are ANSI colors.
+#       The "hi" colors above are recommended as they show up much better on black backgrounds
 #
-#     "regex" is a regular expression matched against a log line
-#         syntax in particular follows https://github.com/google/re2/wiki/Syntax
+#   "regex" is a regular expression matched against a log line
+#       syntax in particular follows https://github.com/google/re2/wiki/Syntax
 syntaxColors = [
     { color="hired", regex=".*ERROR.*" }, # red
     { color="hiyellow", regex=".*WARN.*" }, # yellow
@@ -48,11 +48,23 @@ syntaxColors = [
     { color="hicyan", regex=".*TRACE.*" }, # cyan
 ]
 
+# Select the method for tailing log files
+#   - "filesystem": listens for filesystem notifications that the log file has changed, then reads the file
+#   - "polling": polls the log file for updates at a regular cadence
+#
+#   Defaults to "filesystem"
+#   If you find that you're not picking up log lines, try out "polling"
+tailingMethod = "filesystem"
+
+# Specity the polling time in milliseconds to check for log file updates
+#   Only applies when tailingMethod is set to "polling"
+pollingTimeMS = 10
+
 [server_settings]
 webServerPort = 8884 # Webserver port to listen on
 webServerAddress = "0.0.0.0" # Webserver address to listen on
 
 # Disable CORS checking on the server
-#       This is a security vulnerability if you disable CORS. Please be careful!
-#       Read more here: https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS
+#   This is a security vulnerability if you disable CORS. Please be careful!
+#   Read more here: https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS
 disableCORS = false

main.go

@@ -37,11 +37,19 @@ func main() {
 	// setup message broker
 	pubSub := pubsub.New(1)
 
+	// collect settings for tailingMethod
+	tailingMethod := viper.GetString("tailingMethod")
+	polling := false
+	if tailingMethod == "polling" {
+		polling = true
+	}
+	pollingTimeMS := viper.GetInt("pollingTimeMS")
+
 	// process all log files to watch
 	logFiles := viper.GetStringSlice("logs")
 	for _, logFile := range logFiles {
 		//begin watching the file in a goroutine for concurrency
-		go Follow(logFile, pubSub, patterns)
+		go Follow(logFile, pubSub, patterns, polling, pollingTimeMS)
 	}
 
 	// startup the web server

tailer.go

@@ -5,19 +5,27 @@ import (
 	"github.com/cskr/pubsub"
 	"github.com/jdrews/go-tailer/fswatcher"
 	"github.com/jdrews/go-tailer/glob"
+	"time"
 )
 
 // Follow begins a tailer for the specified logFilePath and publishes log lines to the given pubSub message broker
 // When Follow picks up a log line, it also runs the line through regex via func Colorize
 // to determine if it matches a color pattern
-func Follow(logFilePath string, pubSub *pubsub.PubSub, patterns []CompiledRegexColors) {
+func Follow(logFilePath string, pubSub *pubsub.PubSub, patterns []CompiledRegexColors, polling bool, pollingRateMS int) {
+
+	var tailer fswatcher.FileTailer
 
 	parsedGlob, err := glob.Parse(logFilePath)
 	if err != nil {
 		panic(fmt.Sprintf("%q: failed to parse glob: %q", parsedGlob, err))
 	}
 
-	tailer, err := fswatcher.RunFileTailer([]glob.Glob{parsedGlob}, false, true, logger)
+	if polling {
+		tailer, err = fswatcher.RunPollingFileTailer([]glob.Glob{parsedGlob}, false, true, time.Duration(pollingRateMS)*time.Millisecond, logger)
+	} else {
+		tailer, err = fswatcher.RunFileTailer([]glob.Glob{parsedGlob}, false, true, logger)
+	}
+
 	for line := range tailer.Lines() {
 		logger.Debug(line.Line)
 		logMessage := Colorize(line.Line, line.File, patterns)

tailer_test.go

@@ -36,13 +36,23 @@ func writeALine(t *testing.T, logFilePath string, logString string) {
 	}
 }
 
-// TestFollow is an integration test for the entire backend tailing system
+// TestFollowFilesystem executes the testFollow integration test with the filesystem tailing method
+func TestFollowFilesystem(t *testing.T) {
+	testFollow(t, false, 10)
+}
+
+// TestFollowPolling executes the testFollow integration test with the polling tailing method
+func TestFollowPolling(t *testing.T) {
+	testFollow(t, true, 10)
+}
+
+// testFollow is an integration test for the entire backend tailing system
 //
 //	This test starts up the Follow function, which watches a specified log file,
 //	writes a line to the log file,
 //	and listens for a response on the pubsub topic.
 //	This test also verifies the message was correctly colored.
-func TestFollow(t *testing.T) {
+func testFollow(t *testing.T, polling bool, pollingTimeMS int) {
 	// Enable ANSI colors regardless of terminal state
 	color.NoColor = false
 
@@ -68,7 +78,7 @@ func TestFollow(t *testing.T) {
 	defer pubSub.Unsub(linesChannel, "lines")
 
 	// Run Follow
-	go Follow(logFilePath, pubSub, compiledRegexColors)
+	go Follow(logFilePath, pubSub, compiledRegexColors, polling, pollingTimeMS)
 
 	// Give the fswatcher.RunFileTailer enough time to startup
 	time.Sleep(time.Duration(2000) * time.Millisecond)