feat: custom label shorthands

pkg/provider/docker/config.go

@@ -1,6 +1,7 @@
 package docker
 
 import (
+	"bytes"
 	"context"
 	"errors"
 	"fmt"
@@ -28,15 +29,50 @@ func NewDynConfBuilder(configuration Shared, apiClient client.APIClient, swarm b
 	return &DynConfBuilder{Shared: configuration, apiClient: apiClient, swarm: swarm}
 }
 
+func (p *DynConfBuilder) applyLabels(container *dockerData, model interface{}) {
+	for _, item := range p.LabelMap {
+		value, ok := container.Labels[item.From]
+		if !ok { // label doesn't exist
+			continue
+		}
+
+		writer := &bytes.Buffer{}
+		if err := item.toTpl.Execute(writer, model); err != nil {
+			continue // should never happen?
+		}
+
+		to := writer.String()
+		if item.Value != nil {
+			container.Labels[to] = *item.Value
+		} else {
+			container.Labels[to] = value
+		}
+	}
+}
+
 func (p *DynConfBuilder) build(ctx context.Context, containersInspected []dockerData) *dynamic.Configuration {
 	configurations := make(map[string]*dynamic.Configuration)
 
 	for _, container := range containersInspected {
+		serviceName := getServiceName(container)
+
+		model := struct {
+			Name          string
+			ContainerName string
+			Labels        *map[string]string
+		}{
+			Name:          serviceName,
+			ContainerName: strings.TrimPrefix(container.Name, "/"),
+			Labels:        &container.Labels,
+		}
+
 		containerName := getServiceName(container) + "-" + container.ID
 
 		logger := log.Ctx(ctx).With().Str("container", containerName).Logger()
 		ctxContainer := logger.WithContext(ctx)
 
+		p.applyLabels(&container, model)
+
 		if !p.keepContainer(ctxContainer, container) {
 			continue
 		}
@@ -83,18 +119,6 @@ func (p *DynConfBuilder) build(ctx context.Context, containersInspected []docker
 			continue
 		}
 
-		serviceName := getServiceName(container)
-
-		model := struct {
-			Name          string
-			ContainerName string
-			Labels        map[string]string
-		}{
-			Name:          serviceName,
-			ContainerName: strings.TrimPrefix(container.Name, "/"),
-			Labels:        container.Labels,
-		}
-
 		provider.BuildRouterConfiguration(ctx, confFromLabel.HTTP, serviceName, p.defaultRuleTpl, model)
 
 		configurations[containerName] = confFromLabel