Add alloc_id to sidecar bootstrap

.changelog/12543.txt

@@ -0,0 +1,3 @@
+```release-note:improvement
+connect: automatically set alloc_id in envoy_stats_tags configuration
+```

command/agent/consul/connect.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"net"
 	"strconv"
+	"strings"
 
 	"github.com/hashicorp/consul/api"
 	"github.com/hashicorp/nomad/helper"
@@ -13,7 +14,7 @@ import (
 // newConnect creates a new Consul AgentServiceConnect struct based on a Nomad
 // Connect struct. If the nomad Connect struct is nil, nil will be returned to
 // disable Connect for this service.
-func newConnect(serviceId string, serviceName string, nc *structs.ConsulConnect, networks structs.Networks, ports structs.AllocatedPorts) (*api.AgentServiceConnect, error) {
+func newConnect(serviceID, allocID string, serviceName string, nc *structs.ConsulConnect, networks structs.Networks, ports structs.AllocatedPorts) (*api.AgentServiceConnect, error) {
 	switch {
 	case nc == nil:
 		// no connect stanza means there is no connect service to register
@@ -32,7 +33,7 @@ func newConnect(serviceId string, serviceName string, nc *structs.ConsulConnect,
 		if nc.SidecarService.Port == "" {
 			nc.SidecarService.Port = fmt.Sprintf("%s-%s", structs.ConnectProxyPrefix, serviceName)
 		}
-		sidecarReg, err := connectSidecarRegistration(serviceId, nc.SidecarService, networks, ports)
+		sidecarReg, err := connectSidecarRegistration(serviceID, allocID, nc.SidecarService, networks, ports)
 		if err != nil {
 			return nil, err
 		}
@@ -47,7 +48,7 @@ func newConnect(serviceId string, serviceName string, nc *structs.ConsulConnect,
 // newConnectGateway creates a new Consul AgentServiceConnectProxyConfig struct based on
 // a Nomad Connect struct. If the Nomad Connect struct does not contain a gateway, nil
 // will be returned as this service is not a gateway.
-func newConnectGateway(serviceName string, connect *structs.ConsulConnect) *api.AgentServiceConnectProxyConfig {
+func newConnectGateway(connect *structs.ConsulConnect) *api.AgentServiceConnectProxyConfig {
 	if !connect.IsGateway() {
 		return nil
 	}
@@ -89,7 +90,7 @@ func newConnectGateway(serviceName string, connect *structs.ConsulConnect) *api.
 	return &api.AgentServiceConnectProxyConfig{Config: envoyConfig}
 }
 
-func connectSidecarRegistration(serviceId string, css *structs.ConsulSidecarService, networks structs.Networks, ports structs.AllocatedPorts) (*api.AgentServiceRegistration, error) {
+func connectSidecarRegistration(serviceID, allocID string, css *structs.ConsulSidecarService, networks structs.Networks, ports structs.AllocatedPorts) (*api.AgentServiceRegistration, error) {
 	if css == nil {
 		// no sidecar stanza means there is no sidecar service to register
 		return nil, nil
@@ -100,7 +101,7 @@ func connectSidecarRegistration(serviceId string, css *structs.ConsulSidecarServ
 		return nil, err
 	}
 
-	proxy, err := connectSidecarProxy(css.Proxy, cMapping.To, networks)
+	proxy, err := connectSidecarProxy(allocID, css.Proxy, cMapping.To, networks)
 	if err != nil {
 		return nil, err
 	}
@@ -109,8 +110,8 @@ func connectSidecarRegistration(serviceId string, css *structs.ConsulSidecarServ
 	// ensure service discovery excludes this sidecar from queries
 	// (ex. in the case of Connect upstreams)
 	checks := api.AgentServiceChecks{{
-		Name:         "Connect Sidecar Aliasing " + serviceId,
-		AliasService: serviceId,
+		Name:         "Connect Sidecar Aliasing " + serviceID,
+		AliasService: serviceID,
 	}}
 	if !css.DisableDefaultTCPCheck {
 		checks = append(checks, &api.AgentServiceCheck{
@@ -129,7 +130,7 @@ func connectSidecarRegistration(serviceId string, css *structs.ConsulSidecarServ
 	}, nil
 }
 
-func connectSidecarProxy(proxy *structs.ConsulProxy, cPort int, networks structs.Networks) (*api.AgentServiceConnectProxyConfig, error) {
+func connectSidecarProxy(allocID string, proxy *structs.ConsulProxy, cPort int, networks structs.Networks) (*api.AgentServiceConnectProxyConfig, error) {
 	if proxy == nil {
 		proxy = new(structs.ConsulProxy)
 	}
@@ -142,7 +143,7 @@ func connectSidecarProxy(proxy *structs.ConsulProxy, cPort int, networks structs
 	return &api.AgentServiceConnectProxyConfig{
 		LocalServiceAddress: proxy.LocalServiceAddress,
 		LocalServicePort:    proxy.LocalServicePort,
-		Config:              connectProxyConfig(proxy.Config, cPort),
+		Config:              connectProxyConfig(proxy.Config, cPort, allocID),
 		Upstreams:           connectUpstreams(proxy.Upstreams),
 		Expose:              expose,
 	}, nil
@@ -228,15 +229,42 @@ func connectMeshGateway(in *structs.ConsulMeshGateway) api.MeshGatewayConfig {
 	return gw
 }
 
-func connectProxyConfig(cfg map[string]interface{}, port int) map[string]interface{} {
+func connectProxyConfig(cfg map[string]interface{}, port int, allocID string) map[string]interface{} {
 	if cfg == nil {
 		cfg = make(map[string]interface{})
 	}
 	cfg["bind_address"] = "0.0.0.0"
 	cfg["bind_port"] = port
+	injectAllocID(cfg, allocID)
 	return cfg
 }
 
+// injectAllocID merges allocID into cfg=>envoy_stats_tags
+//
+// cfg must not be nil
+func injectAllocID(cfg map[string]interface{}, allocID string) {
+	const key = "envoy_stats_tags"
+	const prefix = "nomad.alloc_id="
+	pair := prefix + allocID
+	tags, exists := cfg[key]
+	if !exists {
+		cfg[key] = []string{pair}
+		return
+	}
+
+	switch v := tags.(type) {
+	case []string:
+		// scan the existing tags to see if alloc_id= is already set
+		for _, s := range v {
+			if strings.HasPrefix(s, prefix) {
+				return
+			}
+		}
+		v = append(v, pair)
+		cfg[key] = v
+	}
+}
+
 func connectNetworkInvariants(networks structs.Networks) error {
 	if n := len(networks); n != 1 {
 		return fmt.Errorf("Connect only supported with exactly 1 network (found %d)", n)