1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
|
/*
* Copyright 2006 Amazon Technologies, Inc. or its affiliates.
* Amazon, Amazon.com and Carbonado are trademarks or registered trademarks
* of Amazon Technologies, Inc. or its affiliates. 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 com.amazon.carbonado.spi;
import java.util.Map;
import java.util.concurrent.TimeUnit;
import org.cojen.util.WeakIdentityMap;
import com.amazon.carbonado.IsolationLevel;
import com.amazon.carbonado.PersistException;
import com.amazon.carbonado.RepositoryException;
import com.amazon.carbonado.Transaction;
/**
* Generic transaction manager for repositories.
*
* @param <Txn> Transaction implementation
* @author Brian S O'Neill
*/
public abstract class TransactionManager<Txn> {
private static final int OPEN = 0, CLOSED = 1, SUSPENDED = 2;
private final ThreadLocal<TransactionScope<Txn>> mLocalScope;
private final Map<TransactionScope<Txn>, ?> mAllScopes;
private int mState;
public TransactionManager() {
mLocalScope = new ThreadLocal<TransactionScope<Txn>>();
mAllScopes = new WeakIdentityMap();
}
/**
* Returns the thread-local TransactionScope, creating it if needed.
*/
public TransactionScope<Txn> localScope() {
TransactionScope<Txn> scope = mLocalScope.get();
if (scope == null) {
int state;
synchronized (this) {
state = mState;
scope = new TransactionScope<Txn>(this, state != OPEN);
mAllScopes.put(scope, null);
}
mLocalScope.set(scope);
if (state == SUSPENDED) {
// Immediately suspend new scope.
scope.getLock().lock();
}
}
return scope;
}
/**
* Detaches the thread-local TransactionScope from the current thread. It
* can be {@link TransactionScope#attach attached} later, and to any thread
* which does not currently have a TransactionScope.
*
* @return detached thread-local TransactionScope or null if none
*/
/*
public TransactionScope<Txn> detachLocalScope() {
TransactionScope<Txn> scope = mLocalScope.get();
if (scope != null) {
if (!scope.detach()) {
scope = null;
} else {
mLocalScope.remove();
}
}
return scope;
}
*/
// Called by TransactionScope.
/*
void attach(TransactionScope<Txn> scope) {
TransactionScope<Txn> existing = mLocalScope.get();
if (existing == null || existing == scope) {
mLocalScope.set(scope);
} else {
throw new IllegalStateException("Current thread already has a transaction scope");
}
}
*/
/**
* Closes all transaction scopes. Should be called only when repository is
* closed.
*
* @param suspend when true, indefinitely suspend all threads interacting
* with transactions
*/
public synchronized void close(boolean suspend) throws RepositoryException {
if (mState == SUSPENDED) {
// If suspended, attempting to close again will likely deadlock.
return;
}
if (suspend) {
for (TransactionScope<?> scope : mAllScopes.keySet()) {
// Lock scope but don't release it. This prevents other threads
// from beginning work during shutdown, which will likely fail
// along the way.
scope.getLock().lock();
}
}
mState = suspend ? SUSPENDED : CLOSED;
for (TransactionScope<?> scope : mAllScopes.keySet()) {
scope.close();
}
}
/**
* Returns supported isolation level, which may be higher. If isolation
* level cannot go higher (or lower than parent) then return null.
*
* @param parent optional parent transaction
* @param level desired isolation level (may be null)
*/
protected abstract IsolationLevel selectIsolationLevel(Transaction parent,
IsolationLevel level);
/**
* Return true if transactions support "for update" mode.
*
* @since 1.2
*/
protected abstract boolean supportsForUpdate();
/**
* Creates an internal transaction representation, with the optional parent
* transaction. If parent is not null and real nested transactions are not
* supported, simply return parent transaction for supporting fake nested
* transactions.
*
* @param parent optional parent transaction
* @param level required isolation level
* @return new transaction, parent transaction, or possibly null if required
* isolation level is none
*/
protected abstract Txn createTxn(Txn parent, IsolationLevel level) throws Exception;
/**
* Creates an internal transaction representation, with the optional parent
* transaction. If parent is not null and real nested transactions are not
* supported, simply return parent transaction for supporting fake nested
* transactions.
*
* <p>The default implementation of this method just calls the regular
* createTxn method, ignoring the timeout parameter.
*
* @param parent optional parent transaction
* @param level required isolation level
* @param timeout desired timeout for lock acquisition, never negative
* @param unit timeout unit, never null
* @return new transaction, parent transaction, or possibly null if required
* isolation level is none
*/
protected Txn createTxn(Txn parent, IsolationLevel level,
int timeout, TimeUnit unit)
throws Exception
{
return createTxn(parent, level);
}
/**
* Called when a transaction is about to be reused. The default
* implementation of this method does nothing. Override if any preparation
* is required to ready a transaction for reuse.
*
* @param txn transaction to reuse, never null
* @since 1.1.3
*/
protected void reuseTxn(Txn txn) throws Exception {
}
/**
* Commits and closes the given internal transaction.
*
* @return true if transaction object is still valid
*/
protected abstract boolean commitTxn(Txn txn) throws PersistException;
/**
* Aborts and closes the given internal transaction.
*/
protected abstract void abortTxn(Txn txn) throws PersistException;
}
|
