initial commit

.circleci/config.yml

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+version: 2
+jobs:
+  build:
+    docker:
+    - image: circleci/golang
+    working_directory: /go/src/github.com/jakubkulhan/ingress-merge
+    steps:
+    - checkout
+    - setup_remote_docker
+    - run:
+        command: |
+          docker build -t jakubkulhan/ingress-merge:latest .
+          if [ "$CIRCLE_BRANCH" == "master" ]; then
+            docker login --username $DOCKER_USERNAME --password $DOCKER_PASSWORD
+            docker push jakubkulhan/ingress-merge:latest
+          fi
+workflows:
+  version: 2
+  wf:
+    jobs:
+    - build

.gitignore

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+/go.sum

Dockerfile

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+FROM golang:1.11
+
+COPY . /src
+
+RUN set -ex \
+    && cd /src \
+    && CGO_ENABLED=0 GOOS=linux go build -ldflags '-extldflags "-static"' -o /bin/ingress-merge ./cmd/ingress-merge
+
+FROM scratch
+COPY --from=0 /bin/ingress-merge /ingress-merge
+ENTRYPOINT ["/ingress-merge"]
+CMD ["--logtostderr"]

LICENSE

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+Copyright (c) 2018 Jakub Kulhan <jakub.kulhan@gmail.com>
+
+Permission is hereby granted, free of charge, to any person
+obtaining a copy of this software and associated documentation
+files (the "Software"), to deal in the Software without
+restriction, including without limitation the rights to use,
+copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the
+Software is furnished to do so, subject to the following
+conditions:
+
+The above copyright notice and this permission notice shall be
+included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
+OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
+HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+OTHER DEALINGS IN THE SOFTWARE.

README.md

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+# Merge Ingress Controller
+
+Merge [Ingress](https://kubernetes.io/docs/concepts/services-networking/ingress/) Controller combines multiple ingress 
+resources into a new one.
+
+## Motivation
+
+Different ingress controllers [behave differently](https://github.com/kubernetes/ingress-nginx/issues/1539#issue-266008311) 
+when creating _services_/_load balancers_ satisfying the ingress resources of the managed class. Some create single service/LB 
+for all ingress resources, some merge resources according to hosts or TLS certificates, other create separate service/LB 
+per ingress resource.
+
+E.g. AWS ALB Ingress Controller creates a new load balancer for each ingress resource. This can become quite costly. 
+There is [an issue](https://github.com/kubernetes-sigs/aws-alb-ingress-controller/issues/298) to support reusing ALBs 
+across ingress resources, however, it won't be implemented anytime soon.
+
+Merge Ingress Controller allows you to create ingress resources that will be combined together to create a new ingress
+resource that will be managed by different controller.
+
+## Setup
+
+Install via [Helm](https://www.helm.sh/):
+
+```sh
+helm install --namespace kube-system --name ingress-merge ./helm
+```
+
+## Example
+
+Create multiple ingresses & one config map that will provide parameters for the result ingress:
+
+```yaml
+apiVersion: extensions/v1beta1
+kind: Ingress
+metadata:
+  name: foo-ingress
+  annotations:
+    kubernetes.io/ingress.class: merge
+    merge.ingress.kubernetes.io/config: merged-ingress
+spec:
+  rules:
+  - host: foo.example.com
+    http:
+      paths:
+      - path: /
+        backend:
+          serviceName: foo-svc
+          servicePort: 80
+
+---
+apiVersion: extensions/v1beta1
+kind: Ingress
+metadata:
+  name: bar-ingress
+  annotations:
+    kubernetes.io/ingress.class: merge
+    merge.ingress.kubernetes.io/config: merged-ingress
+spec:
+  rules:
+  - host: bar.example.com
+    http:
+      paths:
+      - path: /
+        backend:
+          serviceName: bar-svc
+          servicePort: 80
+
+---
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: merged-ingress
+data:
+  annotations: |
+    kubernetes.io/ingress.class: other
+```
+
+Merge Ingress Controller will create new ingress resource named by the config map with rules combined together:
+
+```yaml
+apiVersion: extensions/v1beta1
+kind: Ingress
+metadata:
+  name: merged-ingress
+  annotations:
+    kubernetes.io/ingress.class: other
+spec:
+  rules:
+  - host: bar.example.com
+    http:
+      paths:
+      - path: /
+        backend:
+          serviceName: bar-svc
+          servicePort: 80
+
+  - host: foo.example.com
+    http:
+      paths:
+      - path: /
+        backend:
+          serviceName: foo-svc
+          servicePort: 80
+```
+
+## Annotations
+
+| Annotation | Default Value | Description | Example |
+|------------|---------------|-------------|---------|
+| `kubernetes.io/ingress.class` | | Use `merge` for this controller to take over. | `kubernetes.io/ingress.class: merge` | 
+| `merge.ingress.kubernetes.io/config` | | Name of the [`ConfigMap`](https://kubernetes.io/docs/tutorials/configuration/) resource that will be used to merge this ingress with others. Because ingresses do not support to reference services across namespaces, neither does this reference. All ingresses to be merged, the config map & the result ingress use the same namespace. | `merge.ingress.kubernetes.io/config: merged-ingress` | 
+| `merge.ingress.kubernetes.io/priority` | `0` | Rules from ingresses with higher priority come in the result ingress rules first. | `merge.ingress.kubernetes.io/priority: 10` |
+| `merge.ingress.kubernetes.io/result` | | Marks ingress created by the controller. If all source ingress resources are deleted, this ingress is deleted as well. | `merge.ingress.kubernetes.io/result: "true"` |
+
+## Configuration keys
+
+| Key | Default Value | Description | Example |
+|-----|---------------|-------------|---------|
+| `name` | _name of the `ConfigMap`_ | Name of the result ingress resource. | `name: my-merged-ingress` |
+| `labels` | | YAML/JSON-serialized labels to be applied to the result ingress. | `labels: '{"app": "loadbalancer", "env": "prod"}'` |
+| `annotations` | `{"merge.ingress.kubernetes.io/result":"true"}` | YAML/JSON-serialized labels to be applied to the result ingress. `merge.ingress.kubernetes.io/result` with value `true` will be always added to the annotations. | `annotations: '{"kubernetes.io/ingress.class": "alb"}` |
+| `backend` | | Default backend for the result ingress (`spec.backend`). Source ingresses **must not** specify default backend (such ingresses won't be merged). | `backend: '{"serviceName": "default-backend-svc", "servicePort": 80}` |
+
+## License
+
+Licensed under MIT license. See `LICENSE` file.

cmd/ingress-merge/main.go

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+package main
+
+import (
+	"context"
+	goflag "flag"
+	"log"
+	"os"
+	"os/signal"
+	"syscall"
+
+	"github.com/golang/glog"
+	"github.com/jakubkulhan/ingress-merge"
+	"github.com/spf13/cobra"
+)
+
+func main() {
+	rootCmd := &cobra.Command{
+		Use:   os.Args[0],
+		Short: "Merge Ingress Controller",
+		RunE: func(cmd *cobra.Command, args []string) error {
+			var (
+				err        error
+				controller = ingress_merge.NewController()
+			)
+
+			if controller.MasterURL, err = cmd.Flags().GetString("apiserver"); err != nil {
+				return err
+			}
+
+			if controller.KubeconfigPath, err = cmd.Flags().GetString("kubeconfig"); err != nil {
+				return err
+			}
+
+			if controller.IngressClass, err = cmd.Flags().GetString("ingress-class"); err != nil {
+				return err
+			}
+
+			ctx, cancel := context.WithCancel(context.Background())
+			interrupts := make(chan os.Signal, 1)
+			go func() {
+				select {
+				case <-interrupts:
+					cancel()
+				}
+			}()
+			signal.Notify(interrupts, syscall.SIGINT, syscall.SIGTERM)
+
+			glog.Infoln("Starting controller")
+
+			return controller.Run(ctx)
+		},
+	}
+
+	rootCmd.PersistentFlags().String(
+		"apiserver",
+		"",
+		"Address of Kubernetes API server.",
+	)
+
+	rootCmd.PersistentFlags().String(
+		"kubeconfig",
+		"",
+		"Path to kubeconfig file.",
+	)
+
+	rootCmd.PersistentFlags().AddGoFlagSet(goflag.CommandLine)
+	goflag.CommandLine.Parse([]string{}) // prevents glog errors
+
+	rootCmd.Flags().String(
+		"ingress-class",
+		"merge",
+		"Process ingress resources with this `kubernetes.io/ingress.class` annotation.",
+	)
+
+	if err := rootCmd.Execute(); err != nil {
+		log.Fatal(err)
+	}
+}