Simplify Encoder's encoding signature.

The reality is that if we ever try to encode a Protocol Buffer and it
fails, it's likely that such an error is ultimately not a runtime error
and should be fixed forthwith.  Thusly, we should rename
``Encoder.Encode`` to ``Encoder.MustEncode`` and drop the error return
value.

coding/interface.go

@@ -14,5 +14,5 @@
 package coding
 
 type Encoder interface {
-	Encode() ([]byte, error)
+	MustEncode() []byte
 }

coding/protocol_buffer.go

@@ -22,15 +22,15 @@ type ProtocolBuffer struct {
 	message proto.Message
 }
 
-func (p ProtocolBuffer) Encode() (raw []byte, err error) {
-	raw, err = proto.Marshal(p.message)
+func (p ProtocolBuffer) MustEncode() []byte {
+	raw, err := proto.Marshal(p.message)
 
 	// XXX: Adjust legacy users of this to not check for error.
 	if err != nil {
 		panic(err)
 	}
 
-	return
+	return raw
 }
 
 func (p ProtocolBuffer) String() string {

storage/metric/curator.go

@@ -341,11 +341,7 @@ func (w watermarkOperator) Operate(key, _ interface{}) (oErr *storage.OperatorEr
 		FirstTimestamp: seriesFrontier.optimalStartTime(curationState),
 	}
 
-	prospectiveKey, err := coding.NewProtocolBuffer(startKey.ToDTO()).Encode()
-	if err != nil {
-		// An encoding failure of a key is no reason to stop.
-		return &storage.OperatorError{error: err, Continuable: true}
-	}
+	prospectiveKey := coding.NewProtocolBuffer(startKey.ToDTO()).MustEncode()
 	if !w.sampleIterator.Seek(prospectiveKey) {
 		// LevelDB is picky about the seek ranges.  If an iterator was invalidated,
 		// no work may occur, and the iterator cannot be recovered.

storage/metric/frontier.go

@@ -115,10 +115,7 @@ func newSeriesFrontier(f model.Fingerprint, d diskFrontier, i leveldb.Iterator)
 		Timestamp:   upperSeek,
 	}
 
-	raw, err := coding.NewProtocolBuffer(key).Encode()
-	if err != nil {
-		panic(err)
-	}
+	raw := coding.NewProtocolBuffer(key).MustEncode()
 	i.Seek(raw)
 
 	if i.Key() == nil {
@@ -160,10 +157,7 @@ func newSeriesFrontier(f model.Fingerprint, d diskFrontier, i leveldb.Iterator)
 
 	key.Timestamp = lowerSeek
 
-	raw, err = coding.NewProtocolBuffer(key).Encode()
-	if err != nil {
-		panic(err)
-	}
+	raw = coding.NewProtocolBuffer(key).MustEncode()
 
 	i.Seek(raw)
 

storage/metric/stochastic_test.go

@@ -194,10 +194,7 @@ func levelDBGetRangeValues(l *LevelDBMetricPersistence, fp model.Fingerprint, i
 		Timestamp:   indexable.EncodeTime(i.OldestInclusive),
 	}
 
-	e, err := coding.NewProtocolBuffer(k).Encode()
-	if err != nil {
-		return
-	}
+	e := coding.NewProtocolBuffer(k).MustEncode()
 
 	iterator := l.MetricSamples.NewIterator(true)
 	defer iterator.Close()

storage/metric/tiered.go

@@ -488,7 +488,7 @@ func (t *TieredStorage) loadChunkAroundTime(iterator leveldb.Iterator, frontier
 	}
 
 	// Try seeking to target key.
-	rawKey, _ := coding.NewProtocolBuffer(targetKey).Encode()
+	rawKey := coding.NewProtocolBuffer(targetKey).MustEncode()
 	iterator.Seek(rawKey)
 
 	foundKey, err := extractSampleKey(iterator)

storage/raw/leveldb/batch.go

@@ -32,24 +32,15 @@ func NewBatch() *batch {
 }
 
 func (b *batch) Drop(key coding.Encoder) {
-	keyEncoded, err := key.Encode()
-	if err != nil {
-		panic(err)
-	}
+	keyEncoded := key.MustEncode()
 	b.drops++
 
 	b.batch.Delete(keyEncoded)
 }
 
 func (b *batch) Put(key, value coding.Encoder) {
-	keyEncoded, err := key.Encode()
-	if err != nil {
-		panic(err)
-	}
-	valueEncoded, err := value.Encode()
-	if err != nil {
-		panic(err)
-	}
+	keyEncoded := key.MustEncode()
+	valueEncoded := value.MustEncode()
 	b.puts++
 
 	b.batch.Put(keyEncoded, valueEncoded)

storage/raw/leveldb/leveldb.go

@@ -251,10 +251,7 @@ func (l *LevelDBPersistence) Close() {
 }
 
 func (l *LevelDBPersistence) Get(value coding.Encoder) (b []byte, err error) {
-	key, err := value.Encode()
-	if err != nil {
-		return
-	}
+	key := value.MustEncode()
 
 	return l.storage.Get(l.readOptions, key)
 }
@@ -271,26 +268,16 @@ func (l *LevelDBPersistence) Has(value coding.Encoder) (h bool, err error) {
 }
 
 func (l *LevelDBPersistence) Drop(value coding.Encoder) (err error) {
-	key, err := value.Encode()
-	if err != nil {
-		return
-	}
-
+	key := value.MustEncode()
 	err = l.storage.Delete(l.writeOptions, key)
 
 	return
 }
 
 func (l *LevelDBPersistence) Put(key, value coding.Encoder) (err error) {
-	keyEncoded, err := key.Encode()
-	if err != nil {
-		return
-	}
+	keyEncoded := key.MustEncode()
 
-	valueEncoded, err := value.Encode()
-	if err != nil {
-		return
-	}
+	valueEncoded := value.MustEncode()
 
 	err = l.storage.Put(l.writeOptions, keyEncoded, valueEncoded)