clientv3/concurrency: software transactional memory

Repeatable read and serialized read STM implementations.

contrib/recipes/stm.go

@@ -1,103 +0,0 @@
-// Copyright 2016 CoreOS, Inc.
-//
-// 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 recipe
-
-import (
-	"github.com/coreos/etcd/Godeps/_workspace/src/golang.org/x/net/context"
-	v3 "github.com/coreos/etcd/clientv3"
-)
-
-// STM implements software transactional memory over etcd
-type STM struct {
-	client *v3.Client
-	// rset holds the read key's value and revision of read
-	rset map[string]*RemoteKV
-	// wset holds the write key and its value
-	wset map[string]string
-	// aborted is whether user aborted the txn
-	aborted bool
-	apply   func(*STM) error
-}
-
-// NewSTM creates new transaction loop for a given apply function.
-func NewSTM(client *v3.Client, apply func(*STM) error) <-chan error {
-	s := &STM{client: client, apply: apply}
-	errc := make(chan error, 1)
-	go func() {
-		var err error
-		for {
-			s.clear()
-			if err = apply(s); err != nil || s.aborted {
-				break
-			}
-			if ok, cerr := s.commit(); ok || cerr != nil {
-				err = cerr
-				break
-			}
-		}
-		errc <- err
-	}()
-	return errc
-}
-
-// Abort abandons the apply loop, letting the transaction close without a commit.
-func (s *STM) Abort() { s.aborted = true }
-
-// Get returns the value for a given key, inserting the key into the txn's rset.
-func (s *STM) Get(key string) (string, error) {
-	if wv, ok := s.wset[key]; ok {
-		return wv, nil
-	}
-	if rk, ok := s.rset[key]; ok {
-		return rk.Value(), nil
-	}
-	rk, err := GetRemoteKV(s.client, key)
-	if err != nil {
-		return "", err
-	}
-	// TODO: setup watchers to abort txn early
-	s.rset[key] = rk
-	return rk.Value(), nil
-}
-
-// Put adds a value for a key to the write set.
-func (s *STM) Put(key string, val string) { s.wset[key] = val }
-
-// commit attempts to apply the txn's changes to the server.
-func (s *STM) commit() (ok bool, rr error) {
-	// read set must not change
-	cmps := make([]v3.Cmp, 0, len(s.rset))
-	for k, rk := range s.rset {
-		// use < to support updating keys that don't exist yet
-		cmp := v3.Compare(v3.ModifiedRevision(k), "<", rk.Revision()+1)
-		cmps = append(cmps, cmp)
-	}
-
-	// apply all writes
-	puts := make([]v3.Op, 0, len(s.wset))
-	for k, v := range s.wset {
-		puts = append(puts, v3.OpPut(k, v))
-	}
-	txnresp, err := s.client.Txn(context.TODO()).If(cmps...).Then(puts...).Commit()
-	if err != nil {
-		return false, err
-	}
-	return txnresp.Succeeded, err
-}
-
-func (s *STM) clear() {
-	s.rset = make(map[string]*RemoteKV)
-	s.wset = make(map[string]string)
-}