Add logging volume metrics to Containerd CRI plugin

Signed-off-by: Sophie Liu <sophieliu@google.com>

pkg/cri/io/logger.go

@@ -143,7 +143,10 @@ func redirectLogs(path string, rc io.ReadCloser, w io.Writer, s StreamType, maxL
 			lineBuffer.Write(l)
 		}
 		lineBuffer.WriteByte(eol)
-		if _, err := lineBuffer.WriteTo(w); err != nil {
+		if n, err := lineBuffer.WriteTo(w); err == nil {
+			outputEntries.Inc()
+			outputBytes.Inc(float64(n))
+		} else {
 			logrus.WithError(err).Errorf("Fail to write %q log to log file %q", s, path)
 			// Continue on write error to drain the container output.
 		}
@@ -153,6 +156,8 @@ func redirectLogs(path string, rc io.ReadCloser, w io.Writer, s StreamType, maxL
 		newLine, isPrefix, err := readLine(r)
 		// NOTE(random-liu): readLine can return actual content even if there is an error.
 		if len(newLine) > 0 {
+			inputEntries.Inc()
+			inputBytes.Inc(float64(len(newLine)))
 			// Buffer returned by ReadLine will change after
 			// next read, copy it.
 			l := make([]byte, len(newLine))
@@ -183,6 +188,7 @@ func redirectLogs(path string, rc io.ReadCloser, w io.Writer, s StreamType, maxL
 			}
 			buf[len(buf)-1] = last[:len(last)-exceedLen]
 			writeLineBuffer(partial, buf)
+			splitEntries.Inc()
 			buf = [][]byte{last[len(last)-exceedLen:]}
 			length = exceedLen
 		}

pkg/cri/io/metrics.go

@@ -0,0 +1,42 @@
+/*
+   Copyright The containerd 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 io
+
+import "github.com/docker/go-metrics"
+
+var (
+	inputEntries  metrics.Counter
+	outputEntries metrics.Counter
+	inputBytes    metrics.Counter
+	outputBytes   metrics.Counter
+	splitEntries  metrics.Counter
+)
+
+func init() {
+	// These CRI metrics record input and output logging volume.
+	ns := metrics.NewNamespace("containerd", "cri", nil)
+
+	inputEntries = ns.NewCounter("input_entries", "Number of log entries received")
+	outputEntries = ns.NewCounter("output_entries", "Number of log entries successfully written to disk")
+	inputBytes = ns.NewCounter("input_bytes", "Size of logs received")
+	outputBytes = ns.NewCounter("output_bytes", "Size of logs successfully written to disk")
+	splitEntries = ns.NewCounter("split_entries", "Number of extra log entries created by splitting the "+
+		"original log entry. This happens when the original log entry exceeds length limit. "+
+		"This metric does not count the original log entry.")
+
+	metrics.Register(ns)
+}