Add metrics for log failures/partials

Signed-off-by: Brian Goff <cpuguy83@gmail.com>

daemon/logger/copier.go

@@ -81,6 +81,7 @@ func (c *Copier) copySrc(name string, src io.Reader) {
 				read, err := src.Read(buf[n:upto])
 				if err != nil {
 					if err != io.EOF {
+						logReadsFailedCount.Inc(1)
 						logrus.Errorf("Error scanning log stream: %s", err)
 						return
 					}
@@ -120,6 +121,7 @@ func (c *Copier) copySrc(name string, src io.Reader) {
 					}
 
 					if logErr := c.dst.Log(msg); logErr != nil {
+						logWritesFailedCount.Inc(1)
 						logrus.Errorf("Failed to log msg %q for logger %s: %s", msg.Line, c.dst.Name(), logErr)
 					}
 				}
@@ -143,6 +145,7 @@ func (c *Copier) copySrc(name string, src io.Reader) {
 						partialid = stringid.GenerateRandomID()
 						ordinal = 1
 						firstPartial = false
+						totalPartialLogs.Inc(1)
 					} else {
 						msg.Timestamp = partialTS
 					}
@@ -151,6 +154,7 @@ func (c *Copier) copySrc(name string, src io.Reader) {
 					hasMorePartial = true
 
 					if logErr := c.dst.Log(msg); logErr != nil {
+						logWritesFailedCount.Inc(1)
 						logrus.Errorf("Failed to log msg %q for logger %s: %s", msg.Line, c.dst.Name(), logErr)
 					}
 					p = 0

daemon/logger/metrics.go

@@ -0,0 +1,21 @@
+package logger // import "github.com/docker/docker/daemon/logger"
+
+import (
+	"github.com/docker/go-metrics"
+)
+
+var (
+	logWritesFailedCount metrics.Counter
+	logReadsFailedCount  metrics.Counter
+	totalPartialLogs     metrics.Counter
+)
+
+func init() {
+	loggerMetrics := metrics.NewNamespace("logger", "", nil)
+
+	logWritesFailedCount = loggerMetrics.NewCounter("log_write_operations_failed", "Number of log write operations that failed")
+	logReadsFailedCount = loggerMetrics.NewCounter("log_read_operations_failed", "Number of log reads from container stdio that failed")
+	totalPartialLogs = loggerMetrics.NewCounter("log_entries_size_greater_than_buffer", "Number of log entries which are larger than the log buffer")
+
+	metrics.Register(loggerMetrics)
+}