add replication registry and local replication

graph/replication.go

@@ -21,6 +21,10 @@ package graph
 // instances. The simplest case is to keep an append-only log of triple
 // changes.
 
+import (
+	"errors"
+)
+
 type Procedure byte
 
 const (
@@ -47,7 +51,31 @@ type Replication interface {
 
 	// Attempt to acquire the given range of triples from other replicated sources.
 	RequestTransactionRange(start int64, end int64)
-
-	// Opens the replication interface.
-	Open(TripleStore, Options)
+}
+
+type NewReplicationFunc func(TripleStore, Options) (Replication, error)
+
+var replicationRegistry = make(map[string]NewReplicationFunc)
+
+func RegisterReplication(name string, newFunc NewReplicationFunc) {
+	if _, found := replicationRegistry[name]; found {
+		panic("already registered Replication " + name)
+	}
+	replicationRegistry[name] = newFunc
+}
+
+func NewReplication(name string, ts TripleStore, opts Options) (Replication, error) {
+	newFunc, hasNew := replicationRegistry[name]
+	if !hasNew {
+		return nil, errors.New("replication: name '" + name + "' is not registered")
+	}
+	return newFunc(ts, opts)
+}
+
+func ReplicationMethods() []string {
+	t := make([]string, 0, len(replicationRegistry))
+	for n := range replicationRegistry {
+		t = append(t, n)
+	}
+	return t
 }

replication/local.go

@@ -0,0 +1,52 @@
+// Copyright 2014 The Cayley Authors. All rights reserved.
+//
+// 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 local
+
+import (
+	"github.com/google/cayley/graph"
+	"sync"
+)
+
+type LocalReplication struct {
+	lastId int64
+	ts     graph.TripleStore
+	mut    sync.Mutex
+}
+
+func NewLocalReplication(ts graph.TripleStore, opts graph.Options) (*LocalReplication, error) {
+	rep := &LocalReplication{lastId: ts.Horizon(), ts: ts}
+	ts.SetReplication(rep)
+	return rep, nil
+}
+
+func (l *LocalReplication) AcquireNextIds(size int64) (start int64, end int64) {
+	l.mut.Lock()
+	defer l.mut.Unlock()
+	start = l.lastId + 1
+	end = l.lastId + size
+	l.lastId += size
+	return
+}
+
+func (l *LocalReplication) GetLastId() int64 {
+	return l.lastId
+}
+
+func (l *LocalReplication) Replicate([]*graph.Transaction)       {}
+func (l *LocalReplication) RequestTransactionRange(int64, int64) {}
+
+func init() {
+	graph.RegisterReplication("local", NewLocalReplication)
+}