001/*
002 * Copyright 2002-2019 the original author or authors.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *      https://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package org.springframework.web.server.session;
018
019import java.time.Clock;
020import java.time.Duration;
021import java.time.Instant;
022import java.time.ZoneId;
023import java.time.temporal.ChronoUnit;
024import java.util.Collections;
025import java.util.Iterator;
026import java.util.Map;
027import java.util.concurrent.ConcurrentHashMap;
028import java.util.concurrent.atomic.AtomicReference;
029import java.util.concurrent.locks.ReentrantLock;
030
031import reactor.core.publisher.Mono;
032import reactor.core.scheduler.Schedulers;
033
034import org.springframework.util.Assert;
035import org.springframework.util.IdGenerator;
036import org.springframework.util.JdkIdGenerator;
037import org.springframework.web.server.WebSession;
038
039/**
040 * Simple Map-based storage for {@link WebSession} instances.
041 *
042 * @author Rossen Stoyanchev
043 * @author Rob Winch
044 * @since 5.0
045 */
046public class InMemoryWebSessionStore implements WebSessionStore {
047
048        private static final IdGenerator idGenerator = new JdkIdGenerator();
049
050
051        private int maxSessions = 10000;
052
053        private Clock clock = Clock.system(ZoneId.of("GMT"));
054
055        private final Map<String, InMemoryWebSession> sessions = new ConcurrentHashMap<>();
056
057        private final ExpiredSessionChecker expiredSessionChecker = new ExpiredSessionChecker();
058
059
060        /**
061         * Set the maximum number of sessions that can be stored. Once the limit is
062         * reached, any attempt to store an additional session will result in an
063         * {@link IllegalStateException}.
064         * <p>By default set to 10000.
065         * @param maxSessions the maximum number of sessions
066         * @since 5.0.8
067         */
068        public void setMaxSessions(int maxSessions) {
069                this.maxSessions = maxSessions;
070        }
071
072        /**
073         * Return the maximum number of sessions that can be stored.
074         * @since 5.0.8
075         */
076        public int getMaxSessions() {
077                return this.maxSessions;
078        }
079
080        /**
081         * Configure the {@link Clock} to use to set lastAccessTime on every created
082         * session and to calculate if it is expired.
083         * <p>This may be useful to align to different timezone or to set the clock
084         * back in a test, e.g. {@code Clock.offset(clock, Duration.ofMinutes(-31))}
085         * in order to simulate session expiration.
086         * <p>By default this is {@code Clock.system(ZoneId.of("GMT"))}.
087         * @param clock the clock to use
088         */
089        public void setClock(Clock clock) {
090                Assert.notNull(clock, "Clock is required");
091                this.clock = clock;
092                removeExpiredSessions();
093        }
094
095        /**
096         * Return the configured clock for session lastAccessTime calculations.
097         */
098        public Clock getClock() {
099                return this.clock;
100        }
101
102        /**
103         * Return the map of sessions with an {@link Collections#unmodifiableMap
104         * unmodifiable} wrapper. This could be used for management purposes, to
105         * list active sessions, invalidate expired ones, etc.
106         * @since 5.0.8
107         */
108        public Map<String, WebSession> getSessions() {
109                return Collections.unmodifiableMap(this.sessions);
110        }
111
112
113        @Override
114        public Mono<WebSession> createWebSession() {
115
116                // Opportunity to clean expired sessions
117                Instant now = this.clock.instant();
118                this.expiredSessionChecker.checkIfNecessary(now);
119
120                return Mono.<WebSession>fromSupplier(() -> new InMemoryWebSession(now))
121                                .subscribeOn(Schedulers.boundedElastic());
122        }
123
124        @Override
125        public Mono<WebSession> retrieveSession(String id) {
126                Instant now = this.clock.instant();
127                this.expiredSessionChecker.checkIfNecessary(now);
128                InMemoryWebSession session = this.sessions.get(id);
129                if (session == null) {
130                        return Mono.empty();
131                }
132                else if (session.isExpired(now)) {
133                        this.sessions.remove(id);
134                        return Mono.empty();
135                }
136                else {
137                        session.updateLastAccessTime(now);
138                        return Mono.just(session);
139                }
140        }
141
142        @Override
143        public Mono<Void> removeSession(String id) {
144                this.sessions.remove(id);
145                return Mono.empty();
146        }
147
148        @Override
149        public Mono<WebSession> updateLastAccessTime(WebSession session) {
150                return Mono.fromSupplier(() -> {
151                        Assert.isInstanceOf(InMemoryWebSession.class, session);
152                        ((InMemoryWebSession) session).updateLastAccessTime(this.clock.instant());
153                        return session;
154                });
155        }
156
157        /**
158         * Check for expired sessions and remove them. Typically such checks are
159         * kicked off lazily during calls to {@link #createWebSession() create} or
160         * {@link #retrieveSession retrieve}, no less than 60 seconds apart.
161         * This method can be called to force a check at a specific time.
162         * @since 5.0.8
163         */
164        public void removeExpiredSessions() {
165                this.expiredSessionChecker.removeExpiredSessions(this.clock.instant());
166        }
167
168
169        private class InMemoryWebSession implements WebSession {
170
171                private final AtomicReference<String> id = new AtomicReference<>(String.valueOf(idGenerator.generateId()));
172
173                private final Map<String, Object> attributes = new ConcurrentHashMap<>();
174
175                private final Instant creationTime;
176
177                private volatile Instant lastAccessTime;
178
179                private volatile Duration maxIdleTime = Duration.ofMinutes(30);
180
181                private final AtomicReference<State> state = new AtomicReference<>(State.NEW);
182
183
184                public InMemoryWebSession(Instant creationTime) {
185                        this.creationTime = creationTime;
186                        this.lastAccessTime = this.creationTime;
187                }
188
189                @Override
190                public String getId() {
191                        return this.id.get();
192                }
193
194                @Override
195                public Map<String, Object> getAttributes() {
196                        return this.attributes;
197                }
198
199                @Override
200                public Instant getCreationTime() {
201                        return this.creationTime;
202                }
203
204                @Override
205                public Instant getLastAccessTime() {
206                        return this.lastAccessTime;
207                }
208
209                @Override
210                public void setMaxIdleTime(Duration maxIdleTime) {
211                        this.maxIdleTime = maxIdleTime;
212                }
213
214                @Override
215                public Duration getMaxIdleTime() {
216                        return this.maxIdleTime;
217                }
218
219                @Override
220                public void start() {
221                        this.state.compareAndSet(State.NEW, State.STARTED);
222                }
223
224                @Override
225                public boolean isStarted() {
226                        return this.state.get().equals(State.STARTED) || !getAttributes().isEmpty();
227                }
228
229                @Override
230                public Mono<Void> changeSessionId() {
231                        String currentId = this.id.get();
232                        InMemoryWebSessionStore.this.sessions.remove(currentId);
233                        String newId = String.valueOf(idGenerator.generateId());
234                        this.id.set(newId);
235                        InMemoryWebSessionStore.this.sessions.put(this.getId(), this);
236                        return Mono.empty();
237                }
238
239                @Override
240                public Mono<Void> invalidate() {
241                        this.state.set(State.EXPIRED);
242                        getAttributes().clear();
243                        InMemoryWebSessionStore.this.sessions.remove(this.id.get());
244                        return Mono.empty();
245                }
246
247                @Override
248                public Mono<Void> save() {
249
250                        checkMaxSessionsLimit();
251
252                        // Implicitly started session..
253                        if (!getAttributes().isEmpty()) {
254                                this.state.compareAndSet(State.NEW, State.STARTED);
255                        }
256
257                        if (isStarted()) {
258                                // Save
259                                InMemoryWebSessionStore.this.sessions.put(this.getId(), this);
260
261                                // Unless it was invalidated
262                                if (this.state.get().equals(State.EXPIRED)) {
263                                        InMemoryWebSessionStore.this.sessions.remove(this.getId());
264                                        return Mono.error(new IllegalStateException("Session was invalidated"));
265                                }
266                        }
267
268                        return Mono.empty();
269                }
270
271                private void checkMaxSessionsLimit() {
272                        if (sessions.size() >= maxSessions) {
273                                expiredSessionChecker.removeExpiredSessions(clock.instant());
274                                if (sessions.size() >= maxSessions) {
275                                        throw new IllegalStateException("Max sessions limit reached: " + sessions.size());
276                                }
277                        }
278                }
279
280                @Override
281                public boolean isExpired() {
282                        return isExpired(clock.instant());
283                }
284
285                private boolean isExpired(Instant now) {
286                        if (this.state.get().equals(State.EXPIRED)) {
287                                return true;
288                        }
289                        if (checkExpired(now)) {
290                                this.state.set(State.EXPIRED);
291                                return true;
292                        }
293                        return false;
294                }
295
296                private boolean checkExpired(Instant currentTime) {
297                        return isStarted() && !this.maxIdleTime.isNegative() &&
298                                        currentTime.minus(this.maxIdleTime).isAfter(this.lastAccessTime);
299                }
300
301                private void updateLastAccessTime(Instant currentTime) {
302                        this.lastAccessTime = currentTime;
303                }
304        }
305
306
307        private class ExpiredSessionChecker {
308
309                /** Max time between expiration checks. */
310                private static final int CHECK_PERIOD = 60 * 1000;
311
312
313                private final ReentrantLock lock = new ReentrantLock();
314
315                private Instant checkTime = clock.instant().plus(CHECK_PERIOD, ChronoUnit.MILLIS);
316
317
318                public void checkIfNecessary(Instant now) {
319                        if (this.checkTime.isBefore(now)) {
320                                removeExpiredSessions(now);
321                        }
322                }
323
324                public void removeExpiredSessions(Instant now) {
325                        if (sessions.isEmpty()) {
326                                return;
327                        }
328                        if (this.lock.tryLock()) {
329                                try {
330                                        Iterator<InMemoryWebSession> iterator = sessions.values().iterator();
331                                        while (iterator.hasNext()) {
332                                                InMemoryWebSession session = iterator.next();
333                                                if (session.isExpired(now)) {
334                                                        iterator.remove();
335                                                        session.invalidate();
336                                                }
337                                        }
338                                }
339                                finally {
340                                        this.checkTime = now.plus(CHECK_PERIOD, ChronoUnit.MILLIS);
341                                        this.lock.unlock();
342                                }
343                        }
344                }
345        }
346
347
348        private enum State { NEW, STARTED, EXPIRED }
349
350}