Implement readiness plugin on node-local-dns

cmd/node-cache/app/cache_app.go

@@ -49,7 +49,8 @@ type ConfigParams struct {
 	CoreFile             string        // Path to config file used by node-cache
 	KubednsCMPath        string        // Directory where kube-dns configmap will be mounted
 	UpstreamSvcName      string        // Name of the service whose clusterIP is the upstream for node-cache for cluster domain
-	HealthPort           string        // port for the healthcheck
+	HealthPort           string        // port for the liveness healthcheck from health plugin
+	ReadyPort            string        // port for the readiness healthcheck from ready plugin
 	SetupIptables        bool
 	SkipTeardown         bool // Indicates whether the iptables rules and interface should be torn down
 }
@@ -142,6 +143,11 @@ func (c *CacheApp) initIptables() {
 				"--dport", c.params.HealthPort, "-j", "NOTRACK", "-m", "comment", "--comment", iptablesCommentSkipConntrack}},
 			{utiliptables.Table("raw"), utiliptables.ChainOutput, []string{"-p", "tcp", "-s", localIP,
 				"--sport", c.params.HealthPort, "-j", "NOTRACK", "-m", "comment", "--comment", iptablesCommentSkipConntrack}},
+			// skip connection tracking for healthcheck requests generated by readiness probe to ready plugin
+			{utiliptables.Table("raw"), utiliptables.ChainOutput, []string{"-p", "tcp", "-d", localIP,
+				"--dport", c.params.ReadyPort, "-j", "NOTRACK", "-m", "comment", "--comment", iptablesCommentSkipConntrack}},
+			{utiliptables.Table("raw"), utiliptables.ChainOutput, []string{"-p", "tcp", "-s", localIP,
+				"--sport", c.params.ReadyPort, "-j", "NOTRACK", "-m", "comment", "--comment", iptablesCommentSkipConntrack}},
 		}...)
 	}
 	c.iptables = newIPTables(c.isIPv6())

cmd/node-cache/main.go

@@ -43,6 +43,7 @@ import (
 	_ "github.com/coredns/coredns/plugin/loop"
 	_ "github.com/coredns/coredns/plugin/metrics"
 	_ "github.com/coredns/coredns/plugin/pprof"
+	_ "github.com/coredns/coredns/plugin/ready"
 	_ "github.com/coredns/coredns/plugin/reload"
 	_ "github.com/coredns/coredns/plugin/rewrite"
 	_ "github.com/coredns/coredns/plugin/template"
@@ -89,6 +90,7 @@ func parseAndValidateFlags() (*app.ConfigParams, error) {
 	flag.StringVar(&params.KubednsCMPath, "kubednscm", "", "Path where the kube-dns configmap will be mounted")
 	flag.StringVar(&params.UpstreamSvcName, "upstreamsvc", "kube-dns", "Service name whose cluster IP is upstream for node-cache")
 	flag.StringVar(&params.HealthPort, "health-port", "8080", "port used by health plugin")
+	flag.StringVar(&params.ReadyPort, "ready-port", "8181", "port used by ready plugin")
 	flag.BoolVar(&params.SkipTeardown, "skipteardown", false, "indicates whether iptables rules should be torn down on exit")
 	flag.Parse()
 
@@ -118,6 +120,9 @@ func parseAndValidateFlags() (*app.ConfigParams, error) {
 	if _, err := strconv.Atoi(params.HealthPort); err != nil {
 		return nil, fmt.Errorf("invalid healthcheck port specified - %q", params.HealthPort)
 	}
+	if _, err := strconv.Atoi(params.ReadyPort); err != nil {
+		return nil, fmt.Errorf("invalid ready port specified - %q", params.ReadyPort)
+	}
 	if f = flag.Lookup("conf"); f != nil {
 		params.CoreFile = f.Value.String()
 		clog.Infof("Using Corefile %s", params.CoreFile)

vendor/modules.txt

@@ -108,6 +108,7 @@ github.com/coredns/coredns/plugin/pkg/uniq
 github.com/coredns/coredns/plugin/pkg/up
 github.com/coredns/coredns/plugin/pkg/upstream
 github.com/coredns/coredns/plugin/pprof
+github.com/coredns/coredns/plugin/ready
 github.com/coredns/coredns/plugin/reload
 github.com/coredns/coredns/plugin/rewrite
 github.com/coredns/coredns/plugin/template