txn.go

Documentation: go.etcd.io/etcd/client/v3

     1  // Copyright 2016 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 clientv3
    16  
    17  import (
    18  	"context"
    19  	"sync"
    20  
    21  	pb "go.etcd.io/etcd/api/v3/etcdserverpb"
    22  
    23  	"google.golang.org/grpc"
    24  )
    25  
    26  // Txn is the interface that wraps mini-transactions.
    27  //
    28  //	Txn(context.TODO()).If(
    29  //	 Compare(Value(k1), ">", v1),
    30  //	 Compare(Version(k1), "=", 2)
    31  //	).Then(
    32  //	 OpPut(k2,v2), OpPut(k3,v3)
    33  //	).Else(
    34  //	 OpPut(k4,v4), OpPut(k5,v5)
    35  //	).Commit()
    36  type Txn interface {
    37  	// If takes a list of comparison. If all comparisons passed in succeed,
    38  	// the operations passed into Then() will be executed. Or the operations
    39  	// passed into Else() will be executed.
    40  	If(cs ...Cmp) Txn
    41  
    42  	// Then takes a list of operations. The Ops list will be executed, if the
    43  	// comparisons passed in If() succeed.
    44  	Then(ops ...Op) Txn
    45  
    46  	// Else takes a list of operations. The Ops list will be executed, if the
    47  	// comparisons passed in If() fail.
    48  	Else(ops ...Op) Txn
    49  
    50  	// Commit tries to commit the transaction.
    51  	Commit() (*TxnResponse, error)
    52  }
    53  
    54  type txn struct {
    55  	kv  *kv
    56  	ctx context.Context
    57  
    58  	mu    sync.Mutex
    59  	cif   bool
    60  	cthen bool
    61  	celse bool
    62  
    63  	isWrite bool
    64  
    65  	cmps []*pb.Compare
    66  
    67  	sus []*pb.RequestOp
    68  	fas []*pb.RequestOp
    69  
    70  	callOpts []grpc.CallOption
    71  }
    72  
    73  func (txn *txn) If(cs ...Cmp) Txn {
    74  	txn.mu.Lock()
    75  	defer txn.mu.Unlock()
    76  
    77  	if txn.cif {
    78  		panic("cannot call If twice!")
    79  	}
    80  
    81  	if txn.cthen {
    82  		panic("cannot call If after Then!")
    83  	}
    84  
    85  	if txn.celse {
    86  		panic("cannot call If after Else!")
    87  	}
    88  
    89  	txn.cif = true
    90  
    91  	for i := range cs {
    92  		txn.cmps = append(txn.cmps, (*pb.Compare)(&cs[i]))
    93  	}
    94  
    95  	return txn
    96  }
    97  
    98  func (txn *txn) Then(ops ...Op) Txn {
    99  	txn.mu.Lock()
   100  	defer txn.mu.Unlock()
   101  
   102  	if txn.cthen {
   103  		panic("cannot call Then twice!")
   104  	}
   105  	if txn.celse {
   106  		panic("cannot call Then after Else!")
   107  	}
   108  
   109  	txn.cthen = true
   110  
   111  	for _, op := range ops {
   112  		txn.isWrite = txn.isWrite || op.isWrite()
   113  		txn.sus = append(txn.sus, op.toRequestOp())
   114  	}
   115  
   116  	return txn
   117  }
   118  
   119  func (txn *txn) Else(ops ...Op) Txn {
   120  	txn.mu.Lock()
   121  	defer txn.mu.Unlock()
   122  
   123  	if txn.celse {
   124  		panic("cannot call Else twice!")
   125  	}
   126  
   127  	txn.celse = true
   128  
   129  	for _, op := range ops {
   130  		txn.isWrite = txn.isWrite || op.isWrite()
   131  		txn.fas = append(txn.fas, op.toRequestOp())
   132  	}
   133  
   134  	return txn
   135  }
   136  
   137  func (txn *txn) Commit() (*TxnResponse, error) {
   138  	txn.mu.Lock()
   139  	defer txn.mu.Unlock()
   140  
   141  	r := &pb.TxnRequest{Compare: txn.cmps, Success: txn.sus, Failure: txn.fas}
   142  
   143  	var resp *pb.TxnResponse
   144  	var err error
   145  	resp, err = txn.kv.remote.Txn(txn.ctx, r, txn.callOpts...)
   146  	if err != nil {
   147  		return nil, toErr(txn.ctx, err)
   148  	}
   149  	return (*TxnResponse)(resp), nil
   150  }
   151
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