Adds Docker provider support

Co-authored-by: Julien Salleyron <julien@containo.us>

provider/configuration.go

@@ -0,0 +1,115 @@
+package provider
+
+import (
+	"context"
+	"reflect"
+	"sort"
+
+	"github.com/containous/traefik/config"
+	"github.com/containous/traefik/log"
+)
+
+// Merge Merges multiple configurations.
+func Merge(ctx context.Context, configurations map[string]*config.Configuration) *config.Configuration {
+	logger := log.FromContext(ctx)
+
+	configuration := &config.Configuration{
+		Routers:     make(map[string]*config.Router),
+		Middlewares: make(map[string]*config.Middleware),
+		Services:    make(map[string]*config.Service),
+	}
+
+	servicesToDelete := map[string]struct{}{}
+	services := map[string][]string{}
+
+	routersToDelete := map[string]struct{}{}
+	routers := map[string][]string{}
+
+	middlewaresToDelete := map[string]struct{}{}
+	middlewares := map[string][]string{}
+
+	var sortedKeys []string
+	for key := range configurations {
+		sortedKeys = append(sortedKeys, key)
+	}
+	sort.Strings(sortedKeys)
+
+	for _, root := range sortedKeys {
+		conf := configurations[root]
+		for serviceName, service := range conf.Services {
+			services[serviceName] = append(services[serviceName], root)
+			if !AddService(configuration, serviceName, service) {
+				servicesToDelete[serviceName] = struct{}{}
+			}
+		}
+
+		for routerName, router := range conf.Routers {
+			routers[routerName] = append(routers[routerName], root)
+			if !AddRouter(configuration, routerName, router) {
+				routersToDelete[routerName] = struct{}{}
+			}
+		}
+
+		for middlewareName, middleware := range conf.Middlewares {
+			middlewares[middlewareName] = append(middlewares[middlewareName], root)
+			if !AddMiddleware(configuration, middlewareName, middleware) {
+				middlewaresToDelete[middlewareName] = struct{}{}
+			}
+		}
+	}
+
+	for serviceName := range servicesToDelete {
+		logger.WithField(log.ServiceName, serviceName).
+			Errorf("Service defined multiple times with different configurations in %v", services[serviceName])
+		delete(configuration.Services, serviceName)
+	}
+
+	for routerName := range routersToDelete {
+		logger.WithField(log.RouterName, routerName).
+			Errorf("Router defined multiple times with different configurations in %v", routers[routerName])
+		delete(configuration.Routers, routerName)
+	}
+
+	for middlewareName := range middlewaresToDelete {
+		logger.WithField(log.MiddlewareName, middlewareName).
+			Errorf("Middleware defined multiple times with different configurations in %v", middlewares[middlewareName])
+		delete(configuration.Middlewares, middlewareName)
+	}
+
+	return configuration
+}
+
+// AddService Adds a service to a configurations.
+func AddService(configuration *config.Configuration, serviceName string, service *config.Service) bool {
+	if _, ok := configuration.Services[serviceName]; !ok {
+		configuration.Services[serviceName] = service
+		return true
+	}
+
+	if !configuration.Services[serviceName].LoadBalancer.Mergeable(service.LoadBalancer) {
+		return false
+	}
+
+	configuration.Services[serviceName].LoadBalancer.Servers = append(configuration.Services[serviceName].LoadBalancer.Servers, service.LoadBalancer.Servers...)
+	return true
+}
+
+// AddRouter Adds a router to a configurations.
+func AddRouter(configuration *config.Configuration, routerName string, router *config.Router) bool {
+	if _, ok := configuration.Routers[routerName]; !ok {
+		configuration.Routers[routerName] = router
+		return true
+	}
+
+	return reflect.DeepEqual(configuration.Routers[routerName], router)
+}
+
+// AddMiddleware Adds a middleware to a configurations.
+func AddMiddleware(configuration *config.Configuration, middlewareName string, middleware *config.Middleware) bool {
+	if _, ok := configuration.Middlewares[middlewareName]; !ok {
+		configuration.Middlewares[middlewareName] = middleware
+		return true
+	}
+
+	return reflect.DeepEqual(configuration.Middlewares[middlewareName], middleware)
+}