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/*
* Copyright 2017-2018 the original author or authors.
*
* 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 org.springframework.data.redis.cache;
import java.nio.charset.StandardCharsets;
import java.time.Duration;
import java.util.Collections;
import java.util.Optional;
import java.util.concurrent.TimeUnit;
import java.util.function.Consumer;
import java.util.function.Function;
import org.springframework.dao.PessimisticLockingFailureException;
import org.springframework.data.redis.connection.RedisConnection;
import org.springframework.data.redis.connection.RedisConnectionFactory;
import org.springframework.data.redis.connection.RedisStringCommands.SetOption;
import org.springframework.data.redis.core.types.Expiration;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
/**
* {@link RedisCacheWriter} implementation capable of reading/writing binary data from/to Redis in {@literal standalone}
* and {@literal cluster} environments. Works upon a given {@link RedisConnectionFactory} to obtain the actual
* {@link RedisConnection}.
* {@link DefaultRedisCacheWriter} can be used in
* {@link RedisCacheWriter#lockingRedisCacheWriter(RedisConnectionFactory) locking} or
* {@link RedisCacheWriter#nonLockingRedisCacheWriter(RedisConnectionFactory) non-locking} mode. While
* {@literal non-locking} aims for maximum performance it may result in overlapping, non atomic, command execution for
* operations spanning multiple Redis interactions like {@code putIfAbsent}. The {@literal locking} counterpart prevents
* command overlap by setting an explicit lock key and checking against presence of this key which leads to additional
* requests and potential command wait times.
*
* @author Christoph Strobl
* @author Mark Paluch
* @since 2.0
*/
class DefaultRedisCacheWriter implements RedisCacheWriter {
private final RedisConnectionFactory connectionFactory;
private final Duration sleepTime;
/**
* @param connectionFactory must not be {@literal null}.
*/
DefaultRedisCacheWriter(RedisConnectionFactory connectionFactory) {
this(connectionFactory, Duration.ZERO);
}
/**
* @param connectionFactory must not be {@literal null}.
* @param sleepTime sleep time between lock request attempts. Must not be {@literal null}. Use {@link Duration#ZERO}
* to disable locking.
*/
DefaultRedisCacheWriter(RedisConnectionFactory connectionFactory, Duration sleepTime) {
Assert.notNull(connectionFactory, "ConnectionFactory must not be null!");
Assert.notNull(sleepTime, "SleepTime must not be null!");
this.connectionFactory = connectionFactory;
this.sleepTime = sleepTime;
}
/*
* (non-Javadoc)
* @see org.springframework.data.redis.cache.RedisCacheWriter#put(java.lang.String, byte[], byte[], java.time.Duration)
*/
@Override
public void put(String name, byte[] key, byte[] value, @Nullable Duration ttl) {
Assert.notNull(name, "Name must not be null!");
Assert.notNull(key, "Key must not be null!");
Assert.notNull(value, "Value must not be null!");
execute(name, connection -> {
if (shouldExpireWithin(ttl)) {
connection.set(key, value, Expiration.from(ttl.toMillis(), TimeUnit.MILLISECONDS), SetOption.upsert());
} else {
connection.set(key, value);
}
return "OK";
});
}
/*
* (non-Javadoc)
* @see org.springframework.data.redis.cache.RedisCacheWriter#get(java.lang.String, byte[])
*/
@Override
public byte[] get(String name, byte[] key) {
Assert.notNull(name, "Name must not be null!");
Assert.notNull(key, "Key must not be null!");
return execute(name, connection -> connection.get(key));
}
/*
* (non-Javadoc)
* @see org.springframework.data.redis.cache.RedisCacheWriter#putIfAbsent(java.lang.String, byte[], byte[], java.time.Duration)
*/
@Override
public byte[] putIfAbsent(String name, byte[] key, byte[] value, @Nullable Duration ttl) {
Assert.notNull(name, "Name must not be null!");
Assert.notNull(key, "Key must not be null!");
Assert.notNull(value, "Value must not be null!");
return execute(name, connection -> {
if (isLockingCacheWriter()) {
doLock(name, connection);
}
try {
if (connection.setNX(key, value)) {
if (shouldExpireWithin(ttl)) {
connection.pExpire(key, ttl.toMillis());
}
return null;
}
return connection.get(key);
} finally {
if (isLockingCacheWriter()) {
doUnlock(name, connection);
}
}
});
}
/*
* (non-Javadoc)
* @see org.springframework.data.redis.cache.RedisCacheWriter#remove(java.lang.String, byte[])
*/
@Override
public void remove(String name, byte[] key) {
Assert.notNull(name, "Name must not be null!");
Assert.notNull(key, "Key must not be null!");
execute(name, connection -> connection.del(key));
}
/*
* (non-Javadoc)
* @see org.springframework.data.redis.cache.RedisCacheWriter#clean(java.lang.String, byte[])
*/
@Override
public void clean(String name, byte[] pattern) {
Assert.notNull(name, "Name must not be null!");
Assert.notNull(pattern, "Pattern must not be null!");
execute(name, connection -> {
boolean wasLocked = false;
try {
if (isLockingCacheWriter()) {
doLock(name, connection);
wasLocked = true;
}
byte[][] keys = Optional.ofNullable(connection.keys(pattern)).orElse(Collections.emptySet())
.toArray(new byte[0][]);
if (keys.length > 0) {
connection.del(keys);
}
} finally {
if (wasLocked && isLockingCacheWriter()) {
doUnlock(name, connection);
}
}
return "OK";
});
}
/**
* Explicitly set a write lock on a cache.
*
* @param name the name of the cache to lock.
*/
void lock(String name) {
execute(name, connection -> doLock(name, connection));
}
/**
* Explicitly remove a write lock from a cache.
*
* @param name the name of the cache to unlock.
*/
void unlock(String name) {
executeLockFree(connection -> doUnlock(name, connection));
}
private Boolean doLock(String name, RedisConnection connection) {
return connection.setNX(createCacheLockKey(name), new byte[0]);
}
private Long doUnlock(String name, RedisConnection connection) {
return connection.del(createCacheLockKey(name));
}
boolean doCheckLock(String name, RedisConnection connection) {
return connection.exists(createCacheLockKey(name));
}
/**
* @return {@literal true} if {@link RedisCacheWriter} uses locks.
*/
private boolean isLockingCacheWriter() {
return !sleepTime.isZero() && !sleepTime.isNegative();
}
private T execute(String name, Function callback) {
RedisConnection connection = connectionFactory.getConnection();
try {
checkAndPotentiallyWaitUntilUnlocked(name, connection);
return callback.apply(connection);
} finally {
connection.close();
}
}
private void executeLockFree(Consumer callback) {
RedisConnection connection = connectionFactory.getConnection();
try {
callback.accept(connection);
} finally {
connection.close();
}
}
private void checkAndPotentiallyWaitUntilUnlocked(String name, RedisConnection connection) {
if (!isLockingCacheWriter()) {
return;
}
try {
while (doCheckLock(name, connection)) {
Thread.sleep(sleepTime.toMillis());
}
} catch (InterruptedException ex) {
// Re-interrupt current thread, to allow other participants to react.
Thread.currentThread().interrupt();
throw new PessimisticLockingFailureException(String.format("Interrupted while waiting to unlock cache %s", name),
ex);
}
}
private static boolean shouldExpireWithin(@Nullable Duration ttl) {
return ttl != null && !ttl.isZero() && !ttl.isNegative();
}
private static byte[] createCacheLockKey(String name) {
return (name + "~lock").getBytes(StandardCharsets.UTF_8);
}
}
