frontend: allow 0 (default) value for healthcheck intervals

While these intervals have a minimum value when set:

    // MinimumDuration puts a minimum on user configured duration.
    // This is to prevent API error on time unit. For example, API may
    // set 3 as healthcheck interval with intention of 3 seconds, but
    // Docker interprets it as 3 nanoseconds.
    const MinimumDuration = 1 * time.Millisecond

It should be possible to set them to `0` (which is teh default). This patch
updates the Dockerfile parser to use the same logic as the docker daemon uses;

    if healthConfig.StartPeriod != 0 && healthConfig.StartPeriod < containertypes.MinimumDuration {
        return errors.Errorf("StartPeriod in Healthcheck cannot be less than %s", containertypes.MinimumDuration)
    }

Signed-off-by: Sebastiaan van Stijn <[email protected]>

Author: thaJeztah

frontend/dockerfile/instructions/parse.go

@@ -37,7 +37,7 @@ func nodeArgs(node *parser.Node) []string {
 		if len(arg.Children) == 0 {
 			result = append(result, arg.Value)
 		} else if len(arg.Children) == 1 {
-			//sub command
+			// sub command
 			result = append(result, arg.Children[0].Value)
 			result = append(result, nodeArgs(arg.Children[0])...)
 		}
@@ -505,6 +505,9 @@ func parseOptInterval(f *Flag) (time.Duration, error) {
 	if err != nil {
 		return 0, err
 	}
+	if d == 0 {
+		return 0, nil
+	}
 	if d < container.MinimumDuration {
 		return 0, fmt.Errorf("Interval %#v cannot be less than %s", f.name, container.MinimumDuration)
 	}

frontend/dockerfile/instructions/parse_test.go

@@ -136,6 +136,10 @@ func TestParseOptInterval(t *testing.T) {
 	require.Error(t, err)
 	require.Contains(t, err.Error(), "cannot be less than 1ms")
 
+	flInterval.Value = "0ms"
+	_, err = parseOptInterval(flInterval)
+	require.NoError(t, err)
+
 	flInterval.Value = "1ms"
 	_, err = parseOptInterval(flInterval)
 	require.NoError(t, err)