e2e: add nsd simple load balancing test

e2e/servicediscovery/input/simple_lb_clients.nomad

@@ -0,0 +1,55 @@
+job "simple_lb_clients" {
+  datacenters = ["dc1"]
+  type        = "batch"
+
+  constraint {
+    attribute = "${attr.kernel.name}"
+    value     = "linux"
+  }
+
+  group "client_1" {
+    task "cat" {
+      driver = "raw_exec"
+      config {
+        command = "bash"
+        args    = ["-c", "sleep 15000"]
+      }
+      resources {
+        cpu    = 10
+        memory = 16
+      }
+      template {
+        destination = "output.txt"
+        data        = <<EOH
+{{$allocID := env "NOMAD_ALLOC_ID" -}}
+{{range nomadService 1 $allocID "db"}}
+  server {{ .Address }}:{{ .Port }}
+{{- end}}
+EOH
+      }
+    }
+  }
+
+  group "client_2" {
+    task "cat" {
+      driver = "raw_exec"
+      config {
+        command = "bash"
+        args    = ["-c", "sleep 15000"]
+      }
+      resources {
+        cpu    = 10
+        memory = 16
+      }
+      template {
+        destination = "output.txt"
+        data        = <<EOH
+{{$allocID := env "NOMAD_ALLOC_ID" -}}
+{{range nomadService 2 $allocID "db"}}
+  server {{ .Address }}:{{ .Port }}
+{{- end}}
+EOH
+      }
+    }
+  }
+}

e2e/servicediscovery/input/simple_lb_replicas.nomad

@@ -0,0 +1,81 @@
+job "simple_lb_replicas" {
+  datacenters = ["dc1"]
+  type        = "service"
+
+  constraint {
+    attribute = "${attr.kernel.name}"
+    value     = "linux"
+  }
+
+  group "db_replica_1" {
+    network {
+      mode = "bridge"
+      port "db_port" {}
+    }
+    service {
+      name     = "db"
+      tags     = ["r1"]
+      port     = "db_port"
+      provider = "nomad"
+    }
+    task "db" {
+      driver = "raw_exec"
+      config {
+        command = "bash"
+        args    = ["-c", "sleep 15000"]
+      }
+      resources {
+        cpu    = 10
+        memory = 16
+      }
+    }
+  }
+
+  group "db_replica_2" {
+    network {
+      mode = "bridge"
+      port "db_port" {}
+    }
+    service {
+      name     = "db"
+      tags     = ["r2"]
+      port     = "db_port"
+      provider = "nomad"
+    }
+    task "db" {
+      driver = "raw_exec"
+      config {
+        command = "bash"
+        args    = ["-c", "sleep 15000"]
+      }
+      resources {
+        cpu    = 10
+        memory = 16
+      }
+    }
+  }
+
+  group "db_replica_3" {
+    network {
+      mode = "bridge"
+      port "db_port" {}
+    }
+    service {
+      name     = "db"
+      tags     = ["r3"]
+      port     = "db_port"
+      provider = "nomad"
+    }
+    task "db" {
+      driver = "raw_exec"
+      config {
+        command = "bash"
+        args    = ["-c", "sleep 15000"]
+      }
+      resources {
+        cpu    = 10
+        memory = 16
+      }
+    }
+  }
+}

e2e/servicediscovery/service_discovery_test.go

@@ -11,12 +11,15 @@ import (
 	"github.com/hashicorp/nomad/e2e/e2eutil"
 	"github.com/hashicorp/nomad/helper/uuid"
 	"github.com/stretchr/testify/require"
+	"golang.org/x/exp/slices"
 )
 
 const (
-	jobNomadProvider  = "./input/nomad_provider.nomad"
-	jobConsulProvider = "./input/consul_provider.nomad"
-	jobMultiProvider  = "./input/multi_provider.nomad"
+	jobNomadProvider    = "./input/nomad_provider.nomad"
+	jobConsulProvider   = "./input/consul_provider.nomad"
+	jobMultiProvider    = "./input/multi_provider.nomad"
+	jobSimpleLBReplicas = "./input/simple_lb_replicas.nomad"
+	jobSimpleLBClients  = "./input/simple_lb_clients.nomad"
 )
 
 const (
@@ -37,6 +40,7 @@ func TestServiceDiscovery(t *testing.T) {
 	// Run our test cases.
 	t.Run("TestServiceDiscovery_MultiProvider", testMultiProvider)
 	t.Run("TestServiceDiscovery_UpdateProvider", testUpdateProvider)
+	t.Run("TestServiceDiscovery_SimpleLoadBalancing", testSimpleLoadBalancing)
 }
 
 // testMultiProvider tests service discovery where multi providers are used
@@ -47,7 +51,7 @@ func testMultiProvider(t *testing.T) {
 	consulClient := e2eutil.ConsulClient(t)
 
 	// Generate our job ID which will be used for the entire test.
-	jobID := "service-discovery-multi-provider-" + uuid.Generate()[:8]
+	jobID := "service-discovery-multi-provider-" + uuid.Short()
 	jobIDs := []string{jobID}
 
 	// Defer a cleanup function to remove the job. This will trigger if the
@@ -92,7 +96,7 @@ func testMultiProvider(t *testing.T) {
 		AllocID:     nomadProviderAllocID,
 		Tags:        []string{"foo", "bar"},
 	}
-	requireEventuallyNomadService(t, &expectedNomadService)
+	requireEventuallyNomadService(t, &expectedNomadService, "")
 
 	// Lookup the service registration in Consul and assert this matches what
 	// we expected.
@@ -205,7 +209,7 @@ func testUpdateProvider(t *testing.T) {
 	const serviceName = "http-api"
 
 	// Generate our job ID which will be used for the entire test.
-	jobID := "service-discovery-update-provider-" + uuid.Generate()[:8]
+	jobID := "service-discovery-update-provider-" + uuid.Short()
 	jobIDs := []string{jobID}
 
 	// Defer a cleanup function to remove the job. This will trigger if the
@@ -241,7 +245,7 @@ func testUpdateProvider(t *testing.T) {
 			AllocID:     nomadProviderAllocID,
 			Tags:        []string{"foo", "bar"},
 		}
-		requireEventuallyNomadService(t, &expectedNomadService)
+		requireEventuallyNomadService(t, &expectedNomadService, "")
 	}
 	nomadServiceTestFn()
 
@@ -320,17 +324,25 @@ func testUpdateProvider(t *testing.T) {
 // against Nomad for a single service. Test cases which expect more than a
 // single response should implement their own assertion, to handle ordering
 // problems.
-func requireEventuallyNomadService(t *testing.T, expected *api.ServiceRegistration) {
+func requireEventuallyNomadService(t *testing.T, expected *api.ServiceRegistration, filter string) {
+	opts := (*api.QueryOptions)(nil)
+	if filter != "" {
+		opts = &api.QueryOptions{
+			Filter: filter,
+		}
+	}
+
 	require.Eventually(t, func() bool {
-		services, _, err := e2eutil.NomadClient(t).Services().Get(expected.ServiceName, nil)
+		services, _, err := e2eutil.NomadClient(t).Services().Get(expected.ServiceName, opts)
 		if err != nil {
 			return false
 		}
 
-		// Perform the checks.
 		if len(services) != 1 {
 			return false
 		}
+
+		// ensure each matching service meets expectations
 		if services[0].ServiceName != expected.ServiceName {
 			return false
 		}
@@ -346,6 +358,11 @@ func requireEventuallyNomadService(t *testing.T, expected *api.ServiceRegistrati
 		if services[0].AllocID != expected.AllocID {
 			return false
 		}
-		return reflect.DeepEqual(services[0].Tags, expected.Tags)
+		if !slices.Equal(services[0].Tags, expected.Tags) {
+			return false
+		}
+
+		return true
+
 	}, defaultWaitForTime, defaultTickTime)
 }

e2e/servicediscovery/simple_lb_test.go

@@ -0,0 +1,74 @@
+package servicediscovery
+
+import (
+	"context"
+	"fmt"
+	"strings"
+	"testing"
+
+	"github.com/hashicorp/nomad/api"
+	"github.com/hashicorp/nomad/e2e/e2eutil"
+	"github.com/hashicorp/nomad/helper/uuid"
+	"github.com/shoenig/test/must"
+)
+
+func testSimpleLoadBalancing(t *testing.T) {
+	nomadClient := e2eutil.NomadClient(t)
+
+	// Generate our job ID which will be used for the entire test.
+	jobID := "nsd-simple-lb-replicas" + uuid.Short()
+	jobIDs := []string{jobID}
+
+	// Defer a cleanup function to remove the job. This will trigger if the
+	// test fails, unless the cancel function is called.
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	defer e2eutil.CleanupJobsAndGCWithContext(t, ctx, &jobIDs)
+
+	// Register the replicas job.
+	allocStubs := e2eutil.RegisterAndWaitForAllocs(t, nomadClient, jobSimpleLBReplicas, jobID, "")
+	must.Len(t, 3, allocStubs)
+
+	for _, stub := range allocStubs {
+		var tag string
+		switch stub.TaskGroup {
+		case "db_replica_1":
+			tag = "r1"
+		case "db_replica_2":
+			tag = "r2"
+		case "db_replica_3":
+			tag = "r3"
+		}
+		expectService := api.ServiceRegistration{
+			ServiceName: "db",
+			Namespace:   api.DefaultNamespace,
+			Datacenter:  "dc1",
+			JobID:       jobID,
+			AllocID:     stub.ID,
+			Tags:        []string{tag},
+		}
+		filter := fmt.Sprintf("Tags contains %q", tag)
+		requireEventuallyNomadService(t, &expectService, filter)
+	}
+
+	jobID2 := "nsd-simple-lb-clients" + uuid.Short()
+	jobIDs = append(jobIDs, jobID2)
+
+	// Register the clients job.
+	allocStubs = e2eutil.RegisterAndWaitForAllocs(t, nomadClient, jobSimpleLBClients, jobID2, "")
+	must.Len(t, 2, allocStubs)
+
+	for _, stub := range allocStubs {
+		var expCount int
+		switch stub.TaskGroup {
+		case "client_1":
+			expCount = 1
+		case "client_2":
+			expCount = 2
+		}
+		must.NoError(t, e2eutil.WaitForAllocFile(stub.ID, "cat/output.txt", func(content string) bool {
+			count := strings.Count(content, "server ")
+			return count == expCount
+		}, nil))
+	}
+}