state: cache state test

state/cache.go

@@ -1,6 +1,8 @@
 package state
 
 import (
+	"reflect"
+
 	"github.com/hashicorp/terraform/terraform"
 )
 
@@ -10,7 +12,8 @@ type CacheState struct {
 	Cache   CacheStateCache
 	Durable CacheStateDurable
 
-	state *terraform.State
+	refreshResult CacheRefreshResult
+	state         *terraform.State
 }
 
 // StateReader impl.
@@ -26,6 +29,7 @@ func (s *CacheState) WriteState(state *terraform.State) error {
 		return err
 	}
 
+	s.state = state
 	return s.Cache.PersistState()
 }
 
@@ -38,9 +42,79 @@ func (s *CacheState) WriteState(state *terraform.State) error {
 //
 // StateRefresher impl.
 func (s *CacheState) RefreshState() error {
+	// Refresh the durable state
+	if err := s.Durable.RefreshState(); err != nil {
+		return err
+	}
+
+	// Refresh the cached state
+	if err := s.Cache.RefreshState(); err != nil {
+		return err
+	}
+
+	// Handle the matrix of cases that can happen when comparing these
+	// two states.
+	cached := s.Cache.State()
+	durable := s.Durable.State()
+	switch {
+	case cached == nil && durable == nil:
+		// Initialized
+		s.refreshResult = CacheRefreshInit
+	case cached != nil && durable == nil:
+		// Cache is newer than remote. Not a big deal, user can just
+		// persist to get correct state.
+		s.refreshResult = CacheRefreshLocalNewer
+	case cached == nil && durable != nil:
+		// Cache should be updated since the remote is set but cache isn't
+		s.refreshResult = CacheRefreshUpdateLocal
+	case durable.Serial < cached.Serial:
+		// Cache is newer than remote. Not a big deal, user can just
+		// persist to get correct state.
+		s.refreshResult = CacheRefreshLocalNewer
+	case durable.Serial > cached.Serial:
+		// Cache should be updated since the remote is newer
+		s.refreshResult = CacheRefreshUpdateLocal
+	case durable.Serial == cached.Serial:
+		// They're supposedly equal, verify.
+		if reflect.DeepEqual(cached, durable) {
+			// Hashes are the same, everything is great
+			s.refreshResult = CacheRefreshNoop
+			break
+		}
+
+		// This is very bad. This means we have two state files that
+		// have the same serial but have a different hash. We can't
+		// reconcile this. The most likely cause is parallel apply
+		// operations.
+		s.refreshResult = CacheRefreshConflict
+
+		// Return early so we don't updtae the state
+		return nil
+	default:
+		panic("unhandled cache refresh state")
+	}
+
+	if s.refreshResult == CacheRefreshUpdateLocal {
+		if err := s.Cache.WriteState(durable); err != nil {
+			s.refreshResult = CacheRefreshNoop
+			return err
+		}
+		if err := s.Cache.PersistState(); err != nil {
+			s.refreshResult = CacheRefreshNoop
+			return err
+		}
+	}
+
+	s.state = cached
+
 	return nil
 }
 
+// RefreshResult returns the result of the last refresh.
+func (s *CacheState) RefreshResult() CacheRefreshResult {
+	return s.refreshResult
+}
+
 // PersistState takes the local cache, assuming it is newer than the remote
 // state, and persists it to the durable storage. If you want to challenge the
 // assumption that the local state is the latest, call a RefreshState prior
@@ -61,11 +135,57 @@ type CacheStateCache interface {
 	StateReader
 	StateWriter
 	StatePersister
+	StateRefresher
 }
 
 // CacheStateDurable is the meta-interface that must be implemented for
 // the durable storage for CacheState.
 type CacheStateDurable interface {
+	StateReader
 	StateWriter
 	StatePersister
+	StateRefresher
 }
+
+// CacheRefreshResult is used to explain the result of the previous
+// RefreshState for a CacheState.
+type CacheRefreshResult int
+
+const (
+	// CacheRefreshNoop indicates nothing has happened,
+	// but that does not indicate an error. Everything is
+	// just up to date. (Push/Pull)
+	CacheRefreshNoop CacheRefreshResult = iota
+
+	// CacheRefreshInit indicates that there is no local or
+	// remote state, and that the state was initialized
+	CacheRefreshInit
+
+	// CacheRefreshUpdateLocal indicates the local state
+	// was updated. (Pull)
+	CacheRefreshUpdateLocal
+
+	// CacheRefreshUpdateRemote indicates the remote state
+	// was updated. (Push)
+	CacheRefreshUpdateRemote
+
+	// CacheRefreshLocalNewer means the pull was a no-op
+	// because the local state is newer than that of the
+	// server. This means a Push should take place. (Pull)
+	CacheRefreshLocalNewer
+
+	// CacheRefreshRemoteNewer means the push was a no-op
+	// because the remote state is newer than that of the
+	// local state. This means a Pull should take place.
+	// (Push)
+	CacheRefreshRemoteNewer
+
+	// CacheRefreshConflict means that the push or pull
+	// was a no-op because there is a conflict. This means
+	// there are multiple state definitions at the same
+	// serial number with different contents. This requires
+	// an operator to intervene and resolve the conflict.
+	// Shame on the user for doing concurrent apply.
+	// (Push/Pull)
+	CacheRefreshConflict
+)

state/cache_test.go

@@ -0,0 +1,58 @@
+package state
+
+import (
+	"os"
+	"reflect"
+	"testing"
+)
+
+func TestCacheState(t *testing.T) {
+	cache := testLocalState(t)
+	durable := testLocalState(t)
+	defer os.Remove(cache.Path)
+	defer os.Remove(durable.Path)
+
+	TestState(t, &CacheState{
+		Cache:   cache,
+		Durable: durable,
+	})
+}
+
+func TestCacheState_persistDurable(t *testing.T) {
+	cache := testLocalState(t)
+	durable := testLocalState(t)
+	defer os.Remove(cache.Path)
+	defer os.Remove(durable.Path)
+
+	cs := &CacheState{
+		Cache:   cache,
+		Durable: durable,
+	}
+
+	state := cache.State()
+	state.Modules = nil
+	if err := cs.WriteState(state); err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	if reflect.DeepEqual(cache.State(), durable.State()) {
+		t.Fatal("cache and durable should not be the same")
+	}
+
+	if err := cs.PersistState(); err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	if !reflect.DeepEqual(cache.State(), durable.State()) {
+		t.Fatalf(
+			"cache and durable should be the same\n\n%#v\n\n%#v",
+			cache.State(), durable.State())
+	}
+}
+
+func TestCacheState_impl(t *testing.T) {
+	var _ StateReader = new(CacheState)
+	var _ StateWriter = new(CacheState)
+	var _ StatePersister = new(CacheState)
+	var _ StateRefresher = new(CacheState)
+}

state/local_test.go

@@ -9,21 +9,9 @@ import (
 )
 
 func TestLocalState(t *testing.T) {
-	f, err := ioutil.TempFile("", "tf")
-	if err != nil {
-		t.Fatalf("err: %s", err)
-	}
-	defer os.Remove(f.Name())
-
-	err = terraform.WriteState(TestStateInitial, f)
-	f.Close()
-	if err != nil {
-		t.Fatalf("err: %s", err)
-	}
-
-	TestState(t, &LocalState{
-		Path: f.Name(),
-	})
+	ls := testLocalState(t)
+	defer os.Remove(ls.Path)
+	TestState(t, ls)
 }
 
 func TestLocalState_impl(t *testing.T) {
@@ -32,3 +20,23 @@ func TestLocalState_impl(t *testing.T) {
 	var _ StatePersister = new(LocalState)
 	var _ StateRefresher = new(LocalState)
 }
+
+func testLocalState(t *testing.T) *LocalState {
+	f, err := ioutil.TempFile("", "tf")
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	err = terraform.WriteState(TestStateInitial(), f)
+	f.Close()
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	ls := &LocalState{Path: f.Name()}
+	if err := ls.RefreshState(); err != nil {
+		t.Fatalf("bad: %s", err)
+	}
+
+	return ls
+}

state/remote/state_test.go

@@ -8,7 +8,7 @@ import (
 
 func TestState(t *testing.T) {
 	s := &State{Client: new(InmemClient)}
-	s.WriteState(state.TestStateInitial)
+	s.WriteState(state.TestStateInitial())
 	if err := s.PersistState(); err != nil {
 		t.Fatalf("err: %s", err)
 	}

state/testing.go

@@ -1,25 +1,13 @@
 package state
 
 import (
+	"bytes"
 	"reflect"
 	"testing"
 
 	"github.com/hashicorp/terraform/terraform"
 )
 
-// TestStateInitial is the initial state that a State should have
-// for TestState.
-var TestStateInitial *terraform.State = &terraform.State{
-	Modules: []*terraform.ModuleState{
-		&terraform.ModuleState{
-			Path: []string{"root", "child"},
-			Outputs: map[string]string{
-				"foo": "bar",
-			},
-		},
-	},
-}
-
 // TestState is a helper for testing state implementations. It is expected
 // that the given implementation is pre-loaded with the TestStateInitial
 // state.
@@ -37,11 +25,12 @@ func TestState(t *testing.T, s interface{}) {
 	}
 
 	// current will track our current state
-	current := TestStateInitial
+	current := TestStateInitial()
+	current.Serial++
 
 	// Check that the initial state is correct
 	if !reflect.DeepEqual(reader.State(), current) {
-		t.Fatalf("not initial: %#v", reader.State())
+		t.Fatalf("not initial: %#v\n\n%#v", reader.State(), current)
 	}
 
 	// Write a new state and verify that we have it
@@ -58,7 +47,7 @@ func TestState(t *testing.T, s interface{}) {
 		}
 
 		if actual := reader.State(); !reflect.DeepEqual(actual, current) {
-			t.Fatalf("bad: %#v", actual)
+			t.Fatalf("bad: %#v\n\n%#v", actual, current)
 		}
 	}
 
@@ -75,8 +64,30 @@ func TestState(t *testing.T, s interface{}) {
 			}
 		}
 
-		if actual := reader.State(); !reflect.DeepEqual(actual, current) {
-			t.Fatalf("bad: %#v", actual)
+		// Just set the serials the same... Then compare.
+		actual := reader.State()
+		actual.Serial = current.Serial
+		if !reflect.DeepEqual(actual, current) {
+			t.Fatalf("bad: %#v\n\n%#v", actual, current)
 		}
 	}
 }
+
+// TestStateInitial is the initial state that a State should have
+// for TestState.
+func TestStateInitial() *terraform.State {
+	initial := &terraform.State{
+		Modules: []*terraform.ModuleState{
+			&terraform.ModuleState{
+				Path: []string{"root", "child"},
+				Outputs: map[string]string{
+					"foo": "bar",
+				},
+			},
+		},
+	}
+
+	var scratch bytes.Buffer
+	terraform.WriteState(initial, &scratch)
+	return initial
+}