From fe7d565803054de4eab0205b092c8bde48ee957f Mon Sep 17 00:00:00 2001
From: Diptanu Choudhury <diptanuc@gmail.com>
Date: Wed, 19 Oct 2016 11:12:25 -0700
Subject: [PATCH] Ensuring that ephemeral disk is present before deciding if we
 should migrate (#1827)

---
 nomad/structs/structs.go      | 12 +++++++++++-
 nomad/structs/structs_test.go | 15 +++++++++++++++
 2 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/nomad/structs/structs.go b/nomad/structs/structs.go
index b6d3e2581..ac2c48443 100644
--- a/nomad/structs/structs.go
+++ b/nomad/structs/structs.go
@@ -3074,7 +3074,17 @@ func (a *Allocation) ShouldMigrate() bool {
 		return false
 	}
 
-	if tg := a.Job.LookupTaskGroup(a.TaskGroup); tg != nil && !tg.EphemeralDisk.Migrate || !tg.EphemeralDisk.Sticky {
+	tg := a.Job.LookupTaskGroup(a.TaskGroup)
+
+	// if the task group is nil or the ephemeral disk block isn't present then
+	// we won't migrate
+	if tg == nil || tg.EphemeralDisk == nil {
+		return false
+	}
+
+	// We won't migrate any data is the user hasn't enabled migration or the
+	// disk is not marked as sticky
+	if !tg.EphemeralDisk.Migrate || !tg.EphemeralDisk.Sticky {
 		return false
 	}
 
diff --git a/nomad/structs/structs_test.go b/nomad/structs/structs_test.go
index 7ce4cfc86..8475c7d94 100644
--- a/nomad/structs/structs_test.go
+++ b/nomad/structs/structs_test.go
@@ -1223,6 +1223,21 @@ func TestAllocation_ShouldMigrate(t *testing.T) {
 	if alloc2.ShouldMigrate() {
 		t.Fatalf("bad: %v", alloc)
 	}
+
+	alloc3 := Allocation{
+		TaskGroup: "foo",
+		Job: &Job{
+			TaskGroups: []*TaskGroup{
+				{
+					Name: "foo",
+				},
+			},
+		},
+	}
+
+	if alloc3.ShouldMigrate() {
+		t.Fatalf("bad: %v", alloc)
+	}
 }
 
 func TestTaskArtifact_Validate_Checksum(t *testing.T) {