From 48e461f7db5f46821db0944160b24038f53e7204 Mon Sep 17 00:00:00 2001
From: Robbie Trencheny <me@robbiet.us>
Date: Sun, 16 Aug 2015 15:02:02 -0700
Subject: [PATCH] Pass through current agent Consul datacenter name

Instead of only filling __meta_consul_dc when datacenter is set in
consul_sd_config this change fills the label based on what the agent
reports it's current data center is, if datacenter isn't manually set,
otherwise it uses whatever datacenter was set to.
---
 retrieval/discovery/consul.go | 22 +++++++++++++++++-----
 1 file changed, 17 insertions(+), 5 deletions(-)

diff --git a/retrieval/discovery/consul.go b/retrieval/discovery/consul.go
index 587af210c..8be65b0d0 100644
--- a/retrieval/discovery/consul.go
+++ b/retrieval/discovery/consul.go
@@ -52,10 +52,11 @@ const (
 // ConsulDiscovery retrieves target information from a Consul server
 // and updates them via watches.
 type ConsulDiscovery struct {
-	client          *consul.Client
-	clientConf      *consul.Config
-	tagSeparator    string
-	scrapedServices map[string]struct{}
+	client           *consul.Client
+	clientConf       *consul.Config
+	clientDatacenter string
+	tagSeparator     string
+	scrapedServices  map[string]struct{}
 
 	mu       sync.RWMutex
 	services map[string]*consulService
@@ -95,6 +96,17 @@ func NewConsulDiscovery(conf *config.ConsulSDConfig) *ConsulDiscovery {
 		scrapedServices: map[string]struct{}{},
 		services:        map[string]*consulService{},
 	}
+	// If the datacenter isn't set in the clientConf, let's get it from the local Consul agent
+	// (Consul default is to use local node's datacenter if one isn't given for a query).
+	if clientConf.Datacenter == "" {
+		info, err := client.Agent().Self()
+		if err != nil {
+			panic(fmt.Errorf("discovery.NewConsulDiscovery: %s", err))
+		}
+		cd.clientDatacenter = info["Config"]["Datacenter"].(string)
+	} else {
+		cd.clientDatacenter = clientConf.Datacenter
+	}
 	for _, name := range conf.Services {
 		cd.scrapedServices[name] = struct{}{}
 	}
@@ -214,7 +226,7 @@ func (cd *ConsulDiscovery) watchServices(update chan<- *consulService, done <-ch
 			}
 			srv.tgroup.Labels = clientmodel.LabelSet{
 				ConsulServiceLabel: clientmodel.LabelValue(name),
-				ConsulDCLabel:      clientmodel.LabelValue(cd.clientConf.Datacenter),
+				ConsulDCLabel:      clientmodel.LabelValue(cd.clientDatacenter),
 			}
 			update <- srv
 		}