Merge flags fix and sample spec for flags (#48)

* Args merge fixed and a flags example spec

* preserve the args order

Author: prateekgogia

operator/docs/examples/cluster-1.21.yaml

@@ -0,0 +1,28 @@
+apiVersion: kit.k8s.sh/v1alpha1
+kind: ControlPlane
+metadata:
+  name: example # Desired Cluster Name
+spec:
+  kubernetesVersion: "1.21"
+  master:
+    apiServer:
+      spec:
+        nodeSelector: 
+          node.kubernetes.io/instance-type: m5.24xlarge
+        containers: 
+        - name: apiserver
+          args: 
+            - --max-requests-inflight=500
+            - --max-mutating-requests-inflight=300
+    controllerManager:
+      spec:
+        containers:
+        - name: controller-manager
+          args:
+            - --kube-api-qps=50
+    scheduler:
+      spec:
+        containers:
+        - name: scheduler
+          args:
+            - --kube-api-qps=50

operator/pkg/utils/patch/patch.go

@@ -19,7 +19,6 @@ import (
 	"fmt"
 	"strings"
 
-	"github.com/awslabs/kit/operator/pkg/utils/functional"
 	v1 "k8s.io/api/core/v1"
 	"k8s.io/apimachinery/pkg/util/strategicpatch"
 )
@@ -57,20 +56,42 @@ func mergePatch(defaultObj, patch, object interface{}) ([]byte, error) {
 	return patchedBytes, nil
 }
 
+// Keep the order of the args same, if the ordering changes when object is patched Kubernetes restarts the pod
 func mergeContainerArgs(defaultSpec, patch *v1.PodSpec) *v1.PodSpec {
-	merged := []string{}
-	for key, value := range functional.UnionStringMaps(parseArgsFor(defaultSpec), parseArgsFor(patch)) {
-		merged = append(merged, strings.Join([]string{key, value}, "="))
+	patchedArgs := parseArgsFor(patch)
+	// get any additional args passed in patch
+	extraArgs := additionalArgs(parseArgsFor(defaultSpec), patch)
+	updatedArgs := []string{}
+	// for all the args in defaultSpec, check if the value for an arg has been updated in patch
+	for _, arg := range defaultSpec.Containers[0].Args {
+		kv := strings.Split(arg, "=")
+		if update, ok := patchedArgs[kv[0]]; ok {
+			kv[1] = update
+		}
+		updatedArgs = append(updatedArgs, strings.Join(kv, "="))
 	}
-	patch.Containers[0].Args = merged
+	patch.Containers[0].Args = append(updatedArgs, extraArgs...)
 	return patch
 }
 
 func parseArgsFor(podSpec *v1.PodSpec) map[string]string {
 	result := map[string]string{}
 	for _, arg := range podSpec.Containers[0].Args {
 		kv := strings.Split(arg, "=")
-		result[kv[0]] = result[kv[1]]
+		result[kv[0]] = kv[1]
+	}
+	return result
+}
+
+// needs to preserve the order of args passed in patch in every iteration
+func additionalArgs(defaultSpec map[string]string, patch *v1.PodSpec) []string {
+	result := make([]string, 0)
+	for _, arg := range patch.Containers[0].Args {
+		kv := strings.Split(arg, "=")
+		if _, ok := defaultSpec[kv[0]]; ok {
+			continue
+		}
+		result = append(result, arg)
 	}
 	return result
 }