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‎.gitignore‎

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.idea
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go.sum
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main

‎README.md‎

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# Dovecot Director Controller
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Dovecot director is used to keep a temporary user -> mail server (= dovecot server) mapping, as described in <a href="https://wiki.dovecot.org/Director">dovecot docs</a>.
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If a dovecot director and dovecot server are used in a kubernetes cluster, mappings are not being updated in case a dovecot container restarts for example.
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To update the new pod ip and therefore to correct the mapping a manual execution of the command "doveadm reload" needs to be done on the dovecot director server.
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Since no one wants to waste manual effort on responses to ordinary container events this tool intends to automatically execute said command on the dovecot director shell whenever a dovecot container/pod becomes ready.
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### Usage
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Runs inside and outside of a kubernetes cluster.
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If you don't run it inside a k8s cluster it tries to load the kubeconfig in the executing users homedir.
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If it does not exist you need to specify the absolute path with command flag "-c".
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Environment variables needed for successful execution:
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* `DOVECOT_DIRECTOR_LABELS`(string): All labels given to dovecot director for conclusive identification of dovecot director pods in the following format: `<LABEL1>=<VALUE1>,<LABEL2>=<VALUE2>`
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* `DOVECOT_LABELS`(string): All labels given to dovecot for conclusive identification of dovecot pods, same format as in `DOVECOT_DIRECTOR_LABELS`
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* `DOVECOT_NAMESPACE`(string): Namespace name which must contain both dovecot director and dovecot pods
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### Used Library
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https://github.com/kubernetes/client-go

‎cmd/main.go‎

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package main
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import (
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"bytes"
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"context"
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"flag"
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"fmt"
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v1 "k8s.io/api/core/v1"
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metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
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"k8s.io/client-go/kubernetes"
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"k8s.io/client-go/kubernetes/scheme"
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"k8s.io/client-go/rest"
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"k8s.io/client-go/tools/cache"
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"k8s.io/client-go/tools/clientcmd"
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"k8s.io/client-go/tools/remotecommand"
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"k8s.io/client-go/util/homedir"
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"os"
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"path/filepath"
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"time"
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)
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// variables: namespace, labels
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var dovecotLabels string
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var dovecotDirectorLabels string
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var namespace string
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var kubeconf *rest.Config
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func main() {
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clientset, err := InClusterAuth()
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if clientset == nil {
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clientset, err = OutOfClusterAuth()
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}
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if err != nil {
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panic(err.Error())
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}
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dovecotDirectorLabels = os.Getenv("DOVECOT_DIRECTOR_LABELS")
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dovecotLabels = os.Getenv("DOVECOT_LABELS")
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namespace = os.Getenv("DOVECOT_NAMESPACE")
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StartWatcher(clientset, namespace)
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}
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func GetPodsByLabel(clientset *kubernetes.Clientset, namespace string, labels string) *v1.PodList {
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listOptions := metav1.ListOptions{
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LabelSelector: labels,
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}
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pods, err := clientset.CoreV1().Pods(namespace).List(context.TODO(), listOptions)
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if err != nil {
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panic(err.Error())
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}
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return pods
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}
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func ExecuteCommand(command string, podname string, namespace string, clientset *kubernetes.Clientset) error {
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cmd := []string{
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"sh",
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"-c",
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command,
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}
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req := clientset.CoreV1().RESTClient().Post().Resource("pods").Name(podname).Namespace(namespace).SubResource("exec")
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// THE FOLLOWING EXPECTS THE POD TO HAVE ONLY ONE CONTAINER IN WHICH THE COMMAND IS GOING TO BE EXECUTED
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option := &v1.PodExecOptions{
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Command: cmd,
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Stdin: false,
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Stdout: true,
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Stderr: true,
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TTY: true,
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}
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req.VersionedParams(
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option,
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scheme.ParameterCodec,
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)
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exec, err := remotecommand.NewSPDYExecutor(kubeconf, "POST", req.URL())
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if err != nil {
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return err
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}
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var stdout, stderr bytes.Buffer
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err = exec.Stream(remotecommand.StreamOptions{
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Stdin: nil,
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Stdout: &stdout,
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Stderr: &stderr,
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Tty: true,
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})
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if err != nil {
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return err
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}
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return nil
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}
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func handleEvent(pod *v1.Pod, clientset *kubernetes.Clientset) {
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switch pod.Status.Phase {
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case v1.PodFailed, v1.PodSucceeded:
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case v1.PodRunning:
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containerStatusSlice := pod.Status.ContainerStatuses
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for _, containerStatus := range containerStatusSlice {
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if containerStatus.Ready {
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podlist := GetPodsByLabel(clientset, namespace, dovecotDirectorLabels)
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for _, dovecotPod := range podlist.Items {
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err := ExecuteCommand(
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"doveadm reload",
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dovecotPod.ObjectMeta.Name,
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namespace,
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clientset)
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if err != nil {
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fmt.Println(err.Error())
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}
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}
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}
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}
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}
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}
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func StartWatcher(clientset *kubernetes.Clientset, namespace string) () {
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optionsModifierFunc := func(options *metav1.ListOptions) {
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options.LabelSelector = dovecotLabels
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}
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watchlist := cache.NewFilteredListWatchFromClient(
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clientset.CoreV1().RESTClient(),
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"pods",
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namespace,
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optionsModifierFunc)
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_, controller := cache.NewInformer(
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watchlist,
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&v1.Pod{},
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time.Second*0,
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cache.ResourceEventHandlerFuncs{
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AddFunc: func(obj interface{}) {
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pod := obj.(*v1.Pod)
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handleEvent(pod, clientset)
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},
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UpdateFunc: func(oldObj, newObj interface{}) {
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pod := newObj.(*v1.Pod)
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handleEvent(pod, clientset)
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},
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},
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)
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go controller.Run(make(chan struct{}))
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for {
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time.Sleep(time.Second)
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}
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}
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func InClusterAuth() (*kubernetes.Clientset, error) {
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var err error
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kubeconf, err = rest.InClusterConfig()
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if err != nil {
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return nil, nil
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}
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clientset, err := kubernetes.NewForConfig(kubeconf)
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if err != nil {
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panic(err.Error())
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}
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return clientset, nil
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}
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func OutOfClusterAuth() (*kubernetes.Clientset, error) {
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var kubeconfig *string
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if home := homedir.HomeDir(); home != "" {
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kubeconfig = flag.String("c", filepath.Join(home, ".kube", "config"), "(optional) absolute path to the kubeconfig file")
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} else {
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kubeconfig = flag.String("c", "", "absolute path to the kubeconfig file")
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}
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flag.Parse()
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var err error
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kubeconf, err = clientcmd.BuildConfigFromFlags("", *kubeconfig)
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if err != nil {
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panic(err.Error())
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}
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clientset, err := kubernetes.NewForConfig(kubeconf)
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if err != nil {
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panic(err.Error())
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}
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return clientset, nil
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}

‎docker/Dockerfile‎

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FROM golang:1.15.3-alpine3.12
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WORKDIR /workdir/go
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ADD cmd/main.go go.mod ./
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RUN go get -d -v ./... && go install -v ./... && go build main.go
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CMD ["main"]

‎docker/build.sh‎

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#!/bin/bash
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docker build --tag dovecot-director-controller:latest -f $(dirname "$0")/Dockerfile $(dirname "$0")/..

‎go.mod‎

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module cmd/main.go
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go 1.15
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require (
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github.com/golang/protobuf v1.4.3 // indirect
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golang.org/x/crypto v0.0.0-20201016220609-9e8e0b390897 // indirect
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golang.org/x/net v0.0.0-20201016165138-7b1cca2348c0 // indirect
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golang.org/x/oauth2 v0.0.0-20200902213428-5d25da1a8d43 // indirect
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golang.org/x/time v0.0.0-20200630173020-3af7569d3a1e // indirect
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k8s.io/api v0.19.2
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k8s.io/apimachinery v0.19.2
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k8s.io/client-go v0.19.2
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k8s.io/utils v0.0.0-20201015054608-420da100c033 // indirect
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)

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