khenaidoo | ffe076b | 2019-01-15 16:08:08 -0500 | [diff] [blame^] | 1 | // Copyright 2017 The etcd Authors |
| 2 | // |
| 3 | // Licensed under the Apache License, Version 2.0 (the "License"); |
| 4 | // you may not use this file except in compliance with the License. |
| 5 | // You may obtain a copy of the License at |
| 6 | // |
| 7 | // http://www.apache.org/licenses/LICENSE-2.0 |
| 8 | // |
| 9 | // Unless required by applicable law or agreed to in writing, software |
| 10 | // distributed under the License is distributed on an "AS IS" BASIS, |
| 11 | // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 12 | // See the License for the specific language governing permissions and |
| 13 | // limitations under the License. |
| 14 | |
| 15 | package ordering |
| 16 | |
| 17 | import ( |
| 18 | "context" |
| 19 | "sync" |
| 20 | |
| 21 | "github.com/coreos/etcd/clientv3" |
| 22 | ) |
| 23 | |
| 24 | // kvOrdering ensures that serialized requests do not return |
| 25 | // get with revisions less than the previous |
| 26 | // returned revision. |
| 27 | type kvOrdering struct { |
| 28 | clientv3.KV |
| 29 | orderViolationFunc OrderViolationFunc |
| 30 | prevRev int64 |
| 31 | revMu sync.RWMutex |
| 32 | } |
| 33 | |
| 34 | func NewKV(kv clientv3.KV, orderViolationFunc OrderViolationFunc) *kvOrdering { |
| 35 | return &kvOrdering{kv, orderViolationFunc, 0, sync.RWMutex{}} |
| 36 | } |
| 37 | |
| 38 | func (kv *kvOrdering) getPrevRev() int64 { |
| 39 | kv.revMu.RLock() |
| 40 | defer kv.revMu.RUnlock() |
| 41 | return kv.prevRev |
| 42 | } |
| 43 | |
| 44 | func (kv *kvOrdering) setPrevRev(currRev int64) { |
| 45 | kv.revMu.Lock() |
| 46 | defer kv.revMu.Unlock() |
| 47 | if currRev > kv.prevRev { |
| 48 | kv.prevRev = currRev |
| 49 | } |
| 50 | } |
| 51 | |
| 52 | func (kv *kvOrdering) Get(ctx context.Context, key string, opts ...clientv3.OpOption) (*clientv3.GetResponse, error) { |
| 53 | // prevRev is stored in a local variable in order to record the prevRev |
| 54 | // at the beginning of the Get operation, because concurrent |
| 55 | // access to kvOrdering could change the prevRev field in the |
| 56 | // middle of the Get operation. |
| 57 | prevRev := kv.getPrevRev() |
| 58 | op := clientv3.OpGet(key, opts...) |
| 59 | for { |
| 60 | r, err := kv.KV.Do(ctx, op) |
| 61 | if err != nil { |
| 62 | return nil, err |
| 63 | } |
| 64 | resp := r.Get() |
| 65 | if resp.Header.Revision == prevRev { |
| 66 | return resp, nil |
| 67 | } else if resp.Header.Revision > prevRev { |
| 68 | kv.setPrevRev(resp.Header.Revision) |
| 69 | return resp, nil |
| 70 | } |
| 71 | err = kv.orderViolationFunc(op, r, prevRev) |
| 72 | if err != nil { |
| 73 | return nil, err |
| 74 | } |
| 75 | } |
| 76 | } |
| 77 | |
| 78 | func (kv *kvOrdering) Txn(ctx context.Context) clientv3.Txn { |
| 79 | return &txnOrdering{ |
| 80 | kv.KV.Txn(ctx), |
| 81 | kv, |
| 82 | ctx, |
| 83 | sync.Mutex{}, |
| 84 | []clientv3.Cmp{}, |
| 85 | []clientv3.Op{}, |
| 86 | []clientv3.Op{}, |
| 87 | } |
| 88 | } |
| 89 | |
| 90 | // txnOrdering ensures that serialized requests do not return |
| 91 | // txn responses with revisions less than the previous |
| 92 | // returned revision. |
| 93 | type txnOrdering struct { |
| 94 | clientv3.Txn |
| 95 | *kvOrdering |
| 96 | ctx context.Context |
| 97 | mu sync.Mutex |
| 98 | cmps []clientv3.Cmp |
| 99 | thenOps []clientv3.Op |
| 100 | elseOps []clientv3.Op |
| 101 | } |
| 102 | |
| 103 | func (txn *txnOrdering) If(cs ...clientv3.Cmp) clientv3.Txn { |
| 104 | txn.mu.Lock() |
| 105 | defer txn.mu.Unlock() |
| 106 | txn.cmps = cs |
| 107 | txn.Txn.If(cs...) |
| 108 | return txn |
| 109 | } |
| 110 | |
| 111 | func (txn *txnOrdering) Then(ops ...clientv3.Op) clientv3.Txn { |
| 112 | txn.mu.Lock() |
| 113 | defer txn.mu.Unlock() |
| 114 | txn.thenOps = ops |
| 115 | txn.Txn.Then(ops...) |
| 116 | return txn |
| 117 | } |
| 118 | |
| 119 | func (txn *txnOrdering) Else(ops ...clientv3.Op) clientv3.Txn { |
| 120 | txn.mu.Lock() |
| 121 | defer txn.mu.Unlock() |
| 122 | txn.elseOps = ops |
| 123 | txn.Txn.Else(ops...) |
| 124 | return txn |
| 125 | } |
| 126 | |
| 127 | func (txn *txnOrdering) Commit() (*clientv3.TxnResponse, error) { |
| 128 | // prevRev is stored in a local variable in order to record the prevRev |
| 129 | // at the beginning of the Commit operation, because concurrent |
| 130 | // access to txnOrdering could change the prevRev field in the |
| 131 | // middle of the Commit operation. |
| 132 | prevRev := txn.getPrevRev() |
| 133 | opTxn := clientv3.OpTxn(txn.cmps, txn.thenOps, txn.elseOps) |
| 134 | for { |
| 135 | opResp, err := txn.KV.Do(txn.ctx, opTxn) |
| 136 | if err != nil { |
| 137 | return nil, err |
| 138 | } |
| 139 | txnResp := opResp.Txn() |
| 140 | if txnResp.Header.Revision >= prevRev { |
| 141 | txn.setPrevRev(txnResp.Header.Revision) |
| 142 | return txnResp, nil |
| 143 | } |
| 144 | err = txn.orderViolationFunc(opTxn, opResp, prevRev) |
| 145 | if err != nil { |
| 146 | return nil, err |
| 147 | } |
| 148 | } |
| 149 | } |