From 1a23b4accfcebef53480026365145db7e277c816 Mon Sep 17 00:00:00 2001
From: Dan Fuhry <dan@fuhry.com>
Date: Fri, 21 Mar 2025 22:49:08 -0400
Subject: [PATCH] [sd] differentiate node name and shard name

Shard is not always applicable to sd entries, but sd entries do need
some kind of discriminator for etcd path collision avoidance.

Use the first element of the hostname for collision avoidance, and make
shard an optional element that nests items one level deeper.
---
 sd/healthcheck.go      |  1 +
 sd/healthcheck_http.go |  6 +++++-
 sd/healthcheck_ldap.go |  6 +++++-
 sd/publish.go          | 32 ++++++++++++++++++++++++--------
 sd/watcher.go          |  7 +++++++
 5 files changed, 42 insertions(+), 10 deletions(-)

diff --git a/sd/healthcheck.go b/sd/healthcheck.go
index fd87d10..89163a3 100644
--- a/sd/healthcheck.go
+++ b/sd/healthcheck.go
@@ -54,6 +54,7 @@ type HealthStatus uint
 type ServiceDefinition struct {
 	Engine       string `json:"type"`
 	ServiceName  string `json:"service_name"`
+	Shard        string `json:"shard"`
 	PollInterval uint   `json:"poll_interval"`
 }
 
diff --git a/sd/healthcheck_http.go b/sd/healthcheck_http.go
index 00a54d9..773af2b 100644
--- a/sd/healthcheck_http.go
+++ b/sd/healthcheck_http.go
@@ -63,6 +63,10 @@ func (hcs *httpHealthCheckService) ServiceDefinition() *ServiceDefinition {
 
 func (hcs *httpHealthCheckService) NewPublisher(domain string, regions []string) *SDPublisher {
 	_, port := hcs.PublishAddress()
+	shard := hcs.serviceDef.Shard
+	if shard == "" {
+		shard = strings.Split(hcs.SocketHost, ".")[0]
+	}
 
 	publisher := &SDPublisher{
 		AdvertiseHost: hcs.SocketHost,
@@ -70,7 +74,7 @@ func (hcs *httpHealthCheckService) NewPublisher(domain string, regions []string)
 		Domain:        domain,
 		Protocol:      ProtocolTCP,
 		Service:       hcs.serviceDef.ServiceName,
-		ShardName:     strings.Split(hcs.SocketHost, ".")[0],
+		ShardName:     shard,
 		Regions:       regions,
 	}
 
diff --git a/sd/healthcheck_ldap.go b/sd/healthcheck_ldap.go
index 5b54ae0..cc00084 100644
--- a/sd/healthcheck_ldap.go
+++ b/sd/healthcheck_ldap.go
@@ -58,6 +58,10 @@ func (lcs *ldapHealthCheckService) ServiceDefinition() *ServiceDefinition {
 
 func (lcs *ldapHealthCheckService) NewPublisher(domain string, regions []string) *SDPublisher {
 	_, port := lcs.PublishAddress()
+	shard := lcs.serviceDef.Shard
+	if shard == "" {
+		shard = strings.Split(lcs.SocketHost, ".")[0]
+	}
 
 	publisher := &SDPublisher{
 		AdvertiseHost: lcs.SocketHost,
@@ -65,7 +69,7 @@ func (lcs *ldapHealthCheckService) NewPublisher(domain string, regions []string)
 		Domain:        domain,
 		Protocol:      ProtocolTCP,
 		Service:       lcs.serviceDef.ServiceName,
-		ShardName:     strings.Split(lcs.SocketHost, ".")[0],
+		ShardName:     shard,
 		Regions:       regions,
 	}
 
diff --git a/sd/publish.go b/sd/publish.go
index 02f01d1..abe5c5b 100644
--- a/sd/publish.go
+++ b/sd/publish.go
@@ -28,6 +28,7 @@ type SDPublisher struct {
 	Domain        string
 	Protocol      Layer4Protocol
 	Service       string
+	NodeName      string
 	ShardName     string
 	LocalRegion   string
 	Regions       []string
@@ -100,8 +101,8 @@ func (s *SDPublisher) init() error {
 		errors = append(errors, "service name was not set")
 	}
 
-	if s.ShardName == "" {
-		s.ShardName = hostname.Hostname()
+	if s.NodeName == "" {
+		s.NodeName = hostname.Hostname()
 	}
 
 	if s.LocalRegion == "" {
@@ -291,12 +292,17 @@ func (s *SDPublisher) renewalTick() {
 
 func (s *SDPublisher) srvRecordPath() string {
 	domainPathComponents := strings.Join(utils.Reverse(strings.Split(s.Domain, ".")), "/")
-	return fmt.Sprintf("/sd/%s/%s/%s/_%s/%s",
+	shardName := ""
+	if s.ShardName != "" {
+		shardName = "/" + s.ShardName
+	}
+	return fmt.Sprintf("/sd/%s/%s/%s/_%s/%s%s",
 		"dns",
 		domainPathComponents,
 		s.Protocol.DNSComponent(),
 		s.Service,
-		s.ShardName)
+		s.NodeName,
+		shardName)
 }
 
 func (s *SDPublisher) srvRecordJson(region string) string {
@@ -316,11 +322,16 @@ func (s *SDPublisher) srvRecordJson(region string) string {
 
 func (s *SDPublisher) aRecordPath() string {
 	domainPathComponents := strings.Join(utils.Reverse(strings.Split(s.Domain, ".")), "/")
-	return fmt.Sprintf("/sd/%s/%s/%s/%s/a",
+	shardName := ""
+	if s.ShardName != "" {
+		shardName = "/" + s.ShardName
+	}
+	return fmt.Sprintf("/sd/%s/%s/%s/%s%s/a",
 		"dns",
 		domainPathComponents,
 		s.Service,
-		s.ShardName)
+		s.NodeName,
+		shardName)
 }
 
 func (s *SDPublisher) aRecordJson() string {
@@ -334,11 +345,16 @@ func (s *SDPublisher) aRecordJson() string {
 
 func (s *SDPublisher) aaaaRecordPath() string {
 	domainPathComponents := strings.Join(utils.Reverse(strings.Split(s.Domain, ".")), "/")
-	return fmt.Sprintf("/sd/%s/%s/%s/%s/aaaa",
+	shardName := ""
+	if s.ShardName != "" {
+		shardName = "/" + s.ShardName
+	}
+	return fmt.Sprintf("/sd/%s/%s/%s/%s%s/aaaa",
 		"dns",
 		domainPathComponents,
 		s.Service,
-		s.ShardName)
+		s.NodeName,
+		shardName)
 }
 
 func (s *SDPublisher) aaaaRecordJson() string {
diff --git a/sd/watcher.go b/sd/watcher.go
index 8eca2e9..5d95d17 100644
--- a/sd/watcher.go
+++ b/sd/watcher.go
@@ -39,6 +39,7 @@ type ServiceAddress struct {
 	IP6      string
 	Protocol Layer4Protocol
 	Service  string
+	Node     string
 	Shard    string
 
 	key string
@@ -208,7 +209,13 @@ func (w *SDWatcher) buildResult(kvs map[string][]byte) []ServiceAddress {
 		if len(components) == 3 {
 			sa.Protocol, _ = Layer4ProtocolFromString(components[0])
 			sa.Service = components[1][1:]
+			sa.Node = components[2]
 			sa.Shard = components[2]
+		} else if len(components) == 4 {
+			sa.Protocol, _ = Layer4ProtocolFromString(components[0])
+			sa.Service = components[1][1:]
+			sa.Node = components[2]
+			sa.Shard = components[3]
 		}
 		sas = append(sas, sa)
 	}
-- 
2.50.1