Merge pull request #95 from prometheus/feature/persistence/batching

Several interface cleanups.

storage/metric/iterator.go

@@ -20,7 +20,3 @@ type Iterator interface {
 	Key() interface{}
 	Value() interface{}
 }
-
-type IteratorManager interface {
-	Iterator() Iterator
-}

storage/raw/index/leveldb/leveldb.go

@@ -16,6 +16,7 @@ package leveldb
 import (
 	"github.com/prometheus/prometheus/coding"
 	dto "github.com/prometheus/prometheus/model/generated"
+	"github.com/prometheus/prometheus/storage/raw"
 	"github.com/prometheus/prometheus/storage/raw/leveldb"
 )
 
@@ -57,6 +58,6 @@ func NewLevelDBMembershipIndex(storageRoot string, cacheCapacity, bitsPerBloomFi
 	return
 }
 
-func (l *LevelDBMembershipIndex) Commit(batch leveldb.Batch) error {
+func (l *LevelDBMembershipIndex) Commit(batch raw.Batch) error {
 	return l.persistence.Commit(batch)
 }

storage/raw/interface.go

@@ -16,6 +16,7 @@ package raw
 import (
 	"github.com/prometheus/prometheus/coding"
 	"github.com/prometheus/prometheus/storage"
+	"io"
 )
 
 type Pair struct {
@@ -25,13 +26,20 @@ type Pair struct {
 
 type EachFunc func(pair *Pair)
 
+// Persistence models a key-value store for bytes that supports various
+// additional operations.
 type Persistence interface {
-	Has(key coding.Encoder) (bool, error)
-	Get(key coding.Encoder) ([]byte, error)
-	Drop(key coding.Encoder) error
-	Put(key, value coding.Encoder) error
-	Close() error
+	io.Closer
 
+	// Has informs the user whether a given key exists in the database.
+	Has(key coding.Encoder) (bool, error)
+	// Get retrieves the key from the database if it exists or returns nil if
+	// it is absent.
+	Get(key coding.Encoder) ([]byte, error)
+	// Drop removes the key from the database.
+	Drop(key coding.Encoder) error
+	// Put sets the key to a given value.
+	Put(key, value coding.Encoder) error
 	// ForEach is responsible for iterating through all records in the database
 	// until one of the following conditions are met:
 	//
@@ -41,7 +49,20 @@ type Persistence interface {
 	//
 	// Decoding errors for an entity cause that entity to be skipped.
 	ForEach(decoder storage.RecordDecoder, filter storage.RecordFilter, operator storage.RecordOperator) (scannedEntireCorpus bool, err error)
-
+	// Commit applies the Batch operations to the database.
+	Commit(Batch) error
 	// Pending removal.
 	GetAll() ([]Pair, error)
 }
+
+// Batch models a pool of mutations for the database that can be committed
+// en masse.  The interface implies no protocol around the atomicity of
+// effectuation.
+type Batch interface {
+	io.Closer
+
+	// Put follows the same protocol as Persistence.Put.
+	Put(key, value coding.Encoder)
+	// Drop follows the same protocol as Persistence.Drop.
+	Drop(key coding.Encoder)
+}

storage/raw/leveldb/batch.go

@@ -0,0 +1,57 @@
+// Copyright 2013 Prometheus Team
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package leveldb
+
+import (
+	"github.com/jmhodges/levigo"
+	"github.com/prometheus/prometheus/coding"
+)
+
+type batch struct {
+	batch *levigo.WriteBatch
+}
+
+func NewBatch() batch {
+	return batch{
+		batch: levigo.NewWriteBatch(),
+	}
+}
+
+func (b batch) Drop(key coding.Encoder) {
+	keyEncoded, err := key.Encode()
+	if err != nil {
+		panic(err)
+	}
+
+	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)
+	}
+
+	b.batch.Put(keyEncoded, valueEncoded)
+}
+
+func (b batch) Close() (err error) {
+	b.batch.Close()
+
+	return
+}

storage/raw/leveldb/leveldb.go

@@ -172,8 +172,17 @@ func (l *LevelDBPersistence) Put(key, value coding.Encoder) (err error) {
 	return
 }
 
-func (l *LevelDBPersistence) Commit(b Batch) (err error) {
-	return l.storage.Write(l.writeOptions, b.(batch).batch)
+func (l *LevelDBPersistence) Commit(b raw.Batch) (err error) {
+	// XXX: This is a wart to clean up later.  Ideally, after doing extensive
+	//      tests, we could create a Batch struct that journals pending
+	//      operations which the given Persistence implementation could convert
+	//      to its specific commit requirements.
+	batch, ok := b.(batch)
+	if !ok {
+		panic("leveldb.batch expected")
+	}
+
+	return l.storage.Write(l.writeOptions, batch.batch)
 }
 
 func (l *LevelDBPersistence) GetAll() (pairs []raw.Pair, err error) {
@@ -229,6 +238,8 @@ func (l *LevelDBPersistence) GetIterator() (i *levigo.Iterator, c io.Closer, err
 	readOptions.SetSnapshot(snapshot)
 	i = l.storage.NewIterator(readOptions)
 
+	// TODO: Kill the return of an additional io.Closer and just use a decorated
+	// iterator interface.
 	c = &iteratorCloser{
 		iterator:    i,
 		readOptions: readOptions,
@@ -279,47 +290,3 @@ func (l *LevelDBPersistence) ForEach(decoder storage.RecordDecoder, filter stora
 	scannedEntireCorpus = true
 	return
 }
-
-// Batch encapsulates a list of mutations to occur to the datastore.  It must
-// be closed once done.
-type Batch interface {
-	Delete(coding.Encoder)
-	Put(coding.Encoder, coding.Encoder)
-	Close()
-}
-
-func NewBatch() Batch {
-	return batch{
-		batch: levigo.NewWriteBatch(),
-	}
-}
-
-type batch struct {
-	batch *levigo.WriteBatch
-}
-
-func (b batch) Delete(key coding.Encoder) {
-	keyEncoded, err := key.Encode()
-	if err != nil {
-		panic(err)
-	}
-
-	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)
-	}
-
-	b.batch.Put(keyEncoded, valueEncoded)
-}
-
-func (b batch) Close() {
-	b.batch.Close()
-}