First iteration of ohmyglb operator

Implements simple GslbResolver CRD/Controller which drives
underlying coredns Deployment

.gitignore

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+# Temporary Build Files
+build/_output
+build/_test
+# Created by https://www.gitignore.io/api/go,vim,emacs,visualstudiocode
+### Emacs ###
+# -*- mode: gitignore; -*-
+*~
+\#*\#
+/.emacs.desktop
+/.emacs.desktop.lock
+*.elc
+auto-save-list
+tramp
+.\#*
+# Org-mode
+.org-id-locations
+*_archive
+# flymake-mode
+*_flymake.*
+# eshell files
+/eshell/history
+/eshell/lastdir
+# elpa packages
+/elpa/
+# reftex files
+*.rel
+# AUCTeX auto folder
+/auto/
+# cask packages
+.cask/
+dist/
+# Flycheck
+flycheck_*.el
+# server auth directory
+/server/
+# projectiles files
+.projectile
+projectile-bookmarks.eld
+# directory configuration
+.dir-locals.el
+# saveplace
+places
+# url cache
+url/cache/
+# cedet
+ede-projects.el
+# smex
+smex-items
+# company-statistics
+company-statistics-cache.el
+# anaconda-mode
+anaconda-mode/
+### Go ###
+# Binaries for programs and plugins
+*.exe
+*.exe~
+*.dll
+*.so
+*.dylib
+# Test binary, build with 'go test -c'
+*.test
+# Output of the go coverage tool, specifically when used with LiteIDE
+*.out
+### Vim ###
+# swap
+.sw[a-p]
+.*.sw[a-p]
+# session
+Session.vim
+# temporary
+.netrwhist
+# auto-generated tag files
+tags
+### VisualStudioCode ###
+.vscode/*
+.history
+# End of https://www.gitignore.io/api/go,vim,emacs,visualstudiocode

build/Dockerfile

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+FROM registry.access.redhat.com/ubi8/ubi-minimal:latest
+
+ENV OPERATOR=/usr/local/bin/ohmyglb \
+    USER_UID=1001 \
+    USER_NAME=ohmyglb
+
+# install operator binary
+COPY build/_output/bin/ohmyglb ${OPERATOR}
+
+COPY build/bin /usr/local/bin
+RUN  /usr/local/bin/user_setup
+
+ENTRYPOINT ["/usr/local/bin/entrypoint"]
+
+USER ${USER_UID}

build/bin/entrypoint

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+#!/bin/sh -e
+
+# This is documented here:
+# https://docs.openshift.com/container-platform/3.11/creating_images/guidelines.html#openshift-specific-guidelines
+
+if ! whoami &>/dev/null; then
+  if [ -w /etc/passwd ]; then
+    echo "${USER_NAME:-ohmyglb}:x:$(id -u):$(id -g):${USER_NAME:-ohmyglb} user:${HOME}:/sbin/nologin" >> /etc/passwd
+  fi
+fi
+
+exec ${OPERATOR} $@

build/bin/user_setup

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+#!/bin/sh
+set -x
+
+# ensure $HOME exists and is accessible by group 0 (we don't know what the runtime UID will be)
+mkdir -p ${HOME}
+chown ${USER_UID}:0 ${HOME}
+chmod ug+rwx ${HOME}
+
+# runtime user will need to be able to self-insert in /etc/passwd
+chmod g+rw /etc/passwd
+
+# no need for this script to remain in the image after running
+rm $0

cmd/manager/main.go

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+package main
+
+import (
+	"context"
+	"flag"
+	"fmt"
+	"os"
+	"runtime"
+
+	// Import all Kubernetes client auth plugins (e.g. Azure, GCP, OIDC, etc.)
+	_ "k8s.io/client-go/plugin/pkg/client/auth"
+	"k8s.io/client-go/rest"
+
+	"github.com/AbsaOSS/ohmyglb/pkg/apis"
+	"github.com/AbsaOSS/ohmyglb/pkg/controller"
+	"github.com/AbsaOSS/ohmyglb/version"
+
+	"github.com/operator-framework/operator-sdk/pkg/k8sutil"
+	kubemetrics "github.com/operator-framework/operator-sdk/pkg/kube-metrics"
+	"github.com/operator-framework/operator-sdk/pkg/leader"
+	"github.com/operator-framework/operator-sdk/pkg/log/zap"
+	"github.com/operator-framework/operator-sdk/pkg/metrics"
+	"github.com/operator-framework/operator-sdk/pkg/restmapper"
+	sdkVersion "github.com/operator-framework/operator-sdk/version"
+	"github.com/spf13/pflag"
+	v1 "k8s.io/api/core/v1"
+	"k8s.io/apimachinery/pkg/util/intstr"
+	"sigs.k8s.io/controller-runtime/pkg/client/config"
+	logf "sigs.k8s.io/controller-runtime/pkg/log"
+	"sigs.k8s.io/controller-runtime/pkg/manager"
+	"sigs.k8s.io/controller-runtime/pkg/manager/signals"
+)
+
+// Change below variables to serve metrics on different host or port.
+var (
+	metricsHost               = "0.0.0.0"
+	metricsPort         int32 = 8383
+	operatorMetricsPort int32 = 8686
+)
+var log = logf.Log.WithName("cmd")
+
+func printVersion() {
+	log.Info(fmt.Sprintf("Operator Version: %s", version.Version))
+	log.Info(fmt.Sprintf("Go Version: %s", runtime.Version()))
+	log.Info(fmt.Sprintf("Go OS/Arch: %s/%s", runtime.GOOS, runtime.GOARCH))
+	log.Info(fmt.Sprintf("Version of operator-sdk: %v", sdkVersion.Version))
+}
+
+func main() {
+	// Add the zap logger flag set to the CLI. The flag set must
+	// be added before calling pflag.Parse().
+	pflag.CommandLine.AddFlagSet(zap.FlagSet())
+
+	// Add flags registered by imported packages (e.g. glog and
+	// controller-runtime)
+	pflag.CommandLine.AddGoFlagSet(flag.CommandLine)
+
+	pflag.Parse()
+
+	// Use a zap logr.Logger implementation. If none of the zap
+	// flags are configured (or if the zap flag set is not being
+	// used), this defaults to a production zap logger.
+	//
+	// The logger instantiated here can be changed to any logger
+	// implementing the logr.Logger interface. This logger will
+	// be propagated through the whole operator, generating
+	// uniform and structured logs.
+	logf.SetLogger(zap.Logger())
+
+	printVersion()
+
+	namespace, err := k8sutil.GetWatchNamespace()
+	if err != nil {
+		log.Error(err, "Failed to get watch namespace")
+		os.Exit(1)
+	}
+
+	// Get a config to talk to the apiserver
+	cfg, err := config.GetConfig()
+	if err != nil {
+		log.Error(err, "")
+		os.Exit(1)
+	}
+
+	ctx := context.TODO()
+	// Become the leader before proceeding
+	err = leader.Become(ctx, "ohmyglb-lock")
+	if err != nil {
+		log.Error(err, "")
+		os.Exit(1)
+	}
+
+	// Create a new Cmd to provide shared dependencies and start components
+	mgr, err := manager.New(cfg, manager.Options{
+		Namespace:          namespace,
+		MapperProvider:     restmapper.NewDynamicRESTMapper,
+		MetricsBindAddress: fmt.Sprintf("%s:%d", metricsHost, metricsPort),
+	})
+	if err != nil {
+		log.Error(err, "")
+		os.Exit(1)
+	}
+
+	log.Info("Registering Components.")
+
+	// Setup Scheme for all resources
+	if err := apis.AddToScheme(mgr.GetScheme()); err != nil {
+		log.Error(err, "")
+		os.Exit(1)
+	}
+
+	// Setup all Controllers
+	if err := controller.AddToManager(mgr); err != nil {
+		log.Error(err, "")
+		os.Exit(1)
+	}
+
+	if err = serveCRMetrics(cfg); err != nil {
+		log.Info("Could not generate and serve custom resource metrics", "error", err.Error())
+	}
+
+	// Add to the below struct any other metrics ports you want to expose.
+	servicePorts := []v1.ServicePort{
+		{Port: metricsPort, Name: metrics.OperatorPortName, Protocol: v1.ProtocolTCP, TargetPort: intstr.IntOrString{Type: intstr.Int, IntVal: metricsPort}},
+		{Port: operatorMetricsPort, Name: metrics.CRPortName, Protocol: v1.ProtocolTCP, TargetPort: intstr.IntOrString{Type: intstr.Int, IntVal: operatorMetricsPort}},
+	}
+	// Create Service object to expose the metrics port(s).
+	service, err := metrics.CreateMetricsService(ctx, cfg, servicePorts)
+	if err != nil {
+		log.Info("Could not create metrics Service", "error", err.Error())
+	}
+
+	// CreateServiceMonitors will automatically create the prometheus-operator ServiceMonitor resources
+	// necessary to configure Prometheus to scrape metrics from this operator.
+	services := []*v1.Service{service}
+	_, err = metrics.CreateServiceMonitors(cfg, namespace, services)
+	if err != nil {
+		log.Info("Could not create ServiceMonitor object", "error", err.Error())
+		// If this operator is deployed to a cluster without the prometheus-operator running, it will return
+		// ErrServiceMonitorNotPresent, which can be used to safely skip ServiceMonitor creation.
+		if err == metrics.ErrServiceMonitorNotPresent {
+			log.Info("Install prometheus-operator in your cluster to create ServiceMonitor objects", "error", err.Error())
+		}
+	}
+
+	log.Info("Starting the Cmd.")
+
+	// Start the Cmd
+	if err := mgr.Start(signals.SetupSignalHandler()); err != nil {
+		log.Error(err, "Manager exited non-zero")
+		os.Exit(1)
+	}
+}
+
+// serveCRMetrics gets the Operator/CustomResource GVKs and generates metrics based on those types.
+// It serves those metrics on "http://metricsHost:operatorMetricsPort".
+func serveCRMetrics(cfg *rest.Config) error {
+	// Below function returns filtered operator/CustomResource specific GVKs.
+	// For more control override the below GVK list with your own custom logic.
+	filteredGVK, err := k8sutil.GetGVKsFromAddToScheme(apis.AddToScheme)
+	if err != nil {
+		return err
+	}
+	// Get the namespace the operator is currently deployed in.
+	operatorNs, err := k8sutil.GetOperatorNamespace()
+	if err != nil {
+		return err
+	}
+	// To generate metrics in other namespaces, add the values below.
+	ns := []string{operatorNs}
+	// Generate and serve custom resource specific metrics.
+	err = kubemetrics.GenerateAndServeCRMetrics(cfg, ns, filteredGVK, metricsHost, operatorMetricsPort)
+	if err != nil {
+		return err
+	}
+	return nil
+}

deploy/crds/ohmyglb.absa.oss_gslbresolvers_crd.yaml

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+apiVersion: apiextensions.k8s.io/v1beta1
+kind: CustomResourceDefinition
+metadata:
+  name: gslbresolvers.ohmyglb.absa.oss
+spec:
+  group: ohmyglb.absa.oss
+  names:
+    kind: GslbResolver
+    listKind: GslbResolverList
+    plural: gslbresolvers
+    singular: gslbresolver
+  scope: Namespaced
+  subresources:
+    status: {}
+  validation:
+    openAPIV3Schema:
+      description: GslbResolver is the Schema for the gslbresolvers API
+      properties:
+        apiVersion:
+          description: 'APIVersion defines the versioned schema of this representation
+            of an object. Servers should convert recognized schemas to the latest
+            internal value, and may reject unrecognized values. More info: https://git.k8s.io/community/contributors/devel/api-conventions.md#resources'
+          type: string
+        kind:
+          description: 'Kind is a string value representing the REST resource this
+            object represents. Servers may infer this from the endpoint the client
+            submits requests to. Cannot be updated. In CamelCase. More info: https://git.k8s.io/community/contributors/devel/api-conventions.md#types-kinds'
+          type: string
+        metadata:
+          type: object
+        spec:
+          description: GslbResolverSpec defines the desired state of GslbResolver
+          properties:
+            size:
+              description: 'INSERT ADDITIONAL SPEC FIELDS - desired state of cluster
+                Important: Run "operator-sdk generate k8s" to regenerate code after
+                modifying this file Add custom validation using kubebuilder tags:
+                https://book-v1.book.kubebuilder.io/beyond_basics/generating_crd.html'
+              format: int32
+              type: integer
+          required:
+          - size
+          type: object
+        status:
+          description: GslbResolverStatus defines the observed state of GslbResolver
+          properties:
+            podNames:
+              description: 'INSERT ADDITIONAL STATUS FIELD - define observed state
+                of cluster Important: Run "operator-sdk generate k8s" to regenerate
+                code after modifying this file Add custom validation using kubebuilder
+                tags: https://book-v1.book.kubebuilder.io/beyond_basics/generating_crd.html'
+              items:
+                type: string
+              type: array
+          required:
+          - podNames
+          type: object
+      type: object
+  version: v1beta1
+  versions:
+  - name: v1beta1
+    served: true
+    storage: true

deploy/crds/ohmyglb.absa.oss_v1beta1_gslbresolver_cr.yaml

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+apiVersion: ohmyglb.absa.oss/v1beta1
+kind: GslbResolver
+metadata:
+  name: example-gslbresolver
+spec:
+  # Add fields here
+  size: 3