util: add health-checker for periodic filesystem checks

Signed-off-by: Niels de Vos <ndevos@ibm.com>

internal/health-checker/filechecker.go

@@ -0,0 +1,118 @@
+/*
+Copyright 2023 ceph-csi 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 healthchecker
+
+import (
+	"errors"
+	"os"
+	"path"
+	"time"
+)
+
+type fileChecker struct {
+	checker
+
+	// filename contains the filename that is used for checking.
+	filename string
+}
+
+func newFileChecker(dir string) ConditionChecker {
+	fc := &fileChecker{
+		filename: path.Join(dir, "csi-volume-condition.ts"),
+	}
+	fc.initDefaults()
+
+	fc.checker.runChecker = func() {
+		fc.isRunning = true
+
+		ticker := time.NewTicker(fc.interval)
+		defer ticker.Stop()
+
+		for {
+			select {
+			case <-fc.commands: // STOP command received
+				fc.isRunning = false
+
+				return
+			case now := <-ticker.C:
+				err := fc.writeTimestamp(now)
+				if err != nil {
+					fc.mutex.Lock()
+					fc.healthy = false
+					fc.err = err
+					fc.mutex.Unlock()
+
+					continue
+				}
+
+				ts, err := fc.readTimestamp()
+				if err != nil {
+					fc.mutex.Lock()
+					fc.healthy = false
+					fc.err = err
+					fc.mutex.Unlock()
+
+					continue
+				}
+
+				// verify that the written timestamp is read back
+				if now.Compare(ts) != 0 {
+					fc.mutex.Lock()
+					fc.healthy = false
+					fc.err = errors.New("timestamp read from file does not match what was written")
+					fc.mutex.Unlock()
+
+					continue
+				}
+
+				// run health check, write a timestamp to a file, read it back
+				fc.mutex.Lock()
+				fc.healthy = true
+				fc.err = nil
+				fc.lastUpdate = ts
+				fc.mutex.Unlock()
+			}
+		}
+	}
+
+	return fc
+}
+
+// readTimestamp reads the JSON formatted timestamp from the file.
+func (fc *fileChecker) readTimestamp() (time.Time, error) {
+	var ts time.Time
+
+	data, err := os.ReadFile(fc.filename)
+	if err != nil {
+		return ts, err
+	}
+
+	err = ts.UnmarshalJSON(data)
+
+	return ts, err
+}
+
+// writeTimestamp writes the timestamp to the file in JSON format.
+func (fc *fileChecker) writeTimestamp(ts time.Time) error {
+	data, err := ts.MarshalJSON()
+	if err != nil {
+		return err
+	}
+
+	//nolint:gosec // allow reading of the timestamp for debugging
+	return os.WriteFile(fc.filename, data, 0o644)
+}