handle read timeout simplification in metrics

metrics.go

@@ -1,6 +1,7 @@
 package tusd
 
 import (
+	"net"
 	"sync"
 	"sync/atomic"
 )
@@ -86,8 +87,18 @@ type simpleHTTPError struct {
 }
 
 func simplifiedHTTPError(err HTTPError) simpleHTTPError {
+	var msg string
+	// Errors for read timeouts contain too much information which is not
+	// necessary for us and makes grouping for the metrics harder. The error
+	// message looks like: read tcp 127.0.0.1:1080->127.0.0.1:53673: i/o timeout
+	// Therefore, we use a common error message for all of them.
+	if netErr, ok := err.(net.Error); ok && netErr.Timeout() {
+		msg = "read tcp: i/o timeout"
+	} else {
+		msg = err.Error()
+	}
 	return simpleHTTPError{
-		Msg:  err.Error(),
+		Msg:  msg,
 		Code: err.StatusCode(),
 	}
 }