#5 prepare macOS file tailer for multiple log file support

Author: fstab

tailer/fileTailer.go

@@ -44,10 +44,6 @@ func (f *fileTailer) Errors() chan Error {
 	return f.errors
 }
 
-func RunFseventFileTailer(path string, readall bool, failOnMissingFile bool, logger simpleLogger) Tailer {
-	return runFileTailer(path, readall, failOnMissingFile, logger, NewFseventWatcher)
-}
-
 func RunPollingFileTailer(path string, readall bool, failOnMissingFile bool, pollIntervall time.Duration, logger simpleLogger) Tailer {
 	makeWatcher := func(abspath string, _ *File) (Watcher, error) {
 		return NewPollingWatcher(abspath, pollIntervall)

tailer/fileTailerLegacyImplWrapper.go

@@ -0,0 +1,22 @@
+// Copyright 2018 The grok_exporter Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build !darwin
+
+package tailer
+
+// old implementation, darwin is already switched to the new implementation, the other OSes will follow
+func RunFseventFileTailer(path string, readall bool, failOnMissingFile bool, logger simpleLogger) Tailer {
+	return runFileTailer(path, readall, failOnMissingFile, logger, NewFseventWatcher)
+}

tailer/fileTailerNewImplWrapper_darwin.go

@@ -0,0 +1,76 @@
+// Copyright 2018 The grok_exporter Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package tailer
+
+import (
+	"fmt"
+	"github.com/fstab/grok_exporter/tailer/fswatcher"
+)
+
+type tailerWrapper struct {
+	lines  chan string
+	errors chan Error
+	done   chan struct{}
+}
+
+func (t *tailerWrapper) Close() {
+	close(t.done)
+	close(t.lines)
+	close(t.errors)
+}
+
+func (t *tailerWrapper) Lines() chan string {
+	return t.lines
+}
+
+func (t *tailerWrapper) Errors() chan Error {
+	return t.errors
+}
+
+// Switch to the new file tailer implementation which supports watching multiple files.
+// Once we switched for all supported operating systems, we can remove the old implementation and the wrapper.
+func RunFseventFileTailer(path string, readall bool, failOnMissingFile bool, _ interface{}) Tailer {
+	result := &tailerWrapper{
+		lines:  make(chan string),
+		errors: make(chan Error),
+		done:   make(chan struct{}),
+	}
+
+	newTailer, err := fswatcher.Run([]string{path}, readall, failOnMissingFile)
+	if err != nil {
+		go func() {
+			result.errors <- newError("failed to initialize file system watcher", err)
+		}()
+		return result
+	}
+
+	go func() {
+		for {
+			select {
+			case l := <-newTailer.Lines():
+				fmt.Printf("*** forwarding line %q to wrapped tailer\n", l.Line)
+				result.lines <- l.Line
+			case e := <-newTailer.Errors():
+				result.errors <- newError(e.Error(), e.Cause())
+				result.Close()
+				return
+			case <-result.done:
+				newTailer.Close()
+				return
+			}
+		}
+	}()
+	return result
+}