Revert "fix: preserve coredns config during cluster restart (#1453)"

This reverts commit 71b5755.

pkg/client/cluster.go

@@ -31,7 +31,6 @@ import (
 	"sort"
 	"strconv"
 	"strings"
-	"text/template"
 	"time"
 
 	"github.com/docker/go-connections/nat"
@@ -55,10 +54,6 @@ import (
 	goyaml "gopkg.in/yaml.v2"
 )
 
-//go:embed templates/coredns-custom.yaml.tmpl
-var customDNSTemplateStr string
-var customDNSTemplate = template.Must(template.New("customDNS").Parse(customDNSTemplateStr))
-
 // ClusterRun orchestrates the steps of cluster creation, configuration and starting
 func ClusterRun(ctx context.Context, runtime k3drt.Runtime, clusterConfig *config.ClusterConfig) error {
 	/*
@@ -1063,18 +1058,11 @@ func ClusterStart(ctx context.Context, runtime k3drt.Runtime, cluster *k3d.Clust
 			// -> inject hostAliases and network members into CoreDNS configmap
 			if len(servers) > 0 {
 				postStartErrgrp.Go(func() error {
-					type record struct {
-						IP       string
-						Hostname string
-					}
-
-					records := make([]record, 0)
+					hosts := ""
 
 					// hosts: hostAliases (including host.k3d.internal)
 					for _, hostAlias := range clusterStartOpts.HostAliases {
-						for _, hostname := range hostAlias.Hostnames {
-							records = append(records, record{IP: hostAlias.IP, Hostname: hostname})
-						}
+						hosts += fmt.Sprintf("%s %s\n", hostAlias.IP, strings.Join(hostAlias.Hostnames, " "))
 					}
 
 					// more hosts: network members ("neighbor" containers)
@@ -1083,21 +1071,45 @@ func ClusterStart(ctx context.Context, runtime k3drt.Runtime, cluster *k3d.Clust
 						return fmt.Errorf("failed to get cluster network %s to inject host records into CoreDNS: %w", cluster.Network.Name, err)
 					}
 					for _, member := range net.Members {
-						records = append(records, record{IP: member.IP.String(), Hostname: member.Name})
+						hosts += fmt.Sprintf("%s %s\n", member.IP.String(), member.Name)
 					}
 
 					// inject CoreDNS configmap
 					l.Log().Infof("Injecting records for hostAliases (incl. host.k3d.internal) and for %d network members into CoreDNS configmap...", len(net.Members))
-					var custom_dns bytes.Buffer
-					err = customDNSTemplate.Execute(&custom_dns, records)
-					if err != nil {
-						return fmt.Errorf("failed to render template: %w", err)
-					}
-					act := actions.WriteFileAction{
+					act := actions.RewriteFileAction{
 						Runtime: runtime,
-						Content: []byte(custom_dns.Bytes()),
-						Dest:    "/var/lib/rancher/k3s/server/manifests/coredns-custom.yaml",
+						Path:    "/var/lib/rancher/k3s/server/manifests/coredns.yaml",
 						Mode:    0744,
+						RewriteFunc: func(input []byte) ([]byte, error) {
+							split, err := util.SplitYAML(input)
+							if err != nil {
+								return nil, fmt.Errorf("error splitting yaml: %w", err)
+							}
+
+							var outputBuf bytes.Buffer
+							outputEncoder := util.NewYAMLEncoder(&outputBuf)
+
+							for _, d := range split {
+								var doc map[string]interface{}
+								if err := yaml.Unmarshal(d, &doc); err != nil {
+									return nil, err
+								}
+								if kind, ok := doc["kind"]; ok {
+									if strings.ToLower(kind.(string)) == "configmap" {
+										configmapData, ok := doc["data"].(map[string]interface{})
+										if !ok {
+											return nil, fmt.Errorf("invalid ConfigMap data type: %T", doc["data"])
+										}
+										configmapData["NodeHosts"] = hosts
+									}
+								}
+								if err := outputEncoder.Encode(doc); err != nil {
+									return nil, err
+								}
+							}
+							_ = outputEncoder.Close()
+							return outputBuf.Bytes(), nil
+						},
 					}
 
 					// get the first server in the list and run action on it once it's ready for it