使用Jedis面臨的非線(xiàn)程安全問(wèn)題詳解
網(wǎng)上都說(shuō)jedis實(shí)例是非線(xiàn)程安全的，常常通過(guò)JedisPool連接池去管理實(shí)例，在多線(xiàn)程情況下讓每個(gè)線(xiàn)程有自己獨(dú)立的jedis實(shí)例，但都沒(méi)有具體說(shuō)明為啥jedis實(shí)例時(shí)非線(xiàn)程安全的，下面詳細(xì)看一下非線(xiàn)程安全主要從哪個(gè)角度來(lái)看。
1. jedis類(lèi)圖
2. 為什么jedis不是線(xiàn)程安全的
由上述類(lèi)圖可知，Jedis類(lèi)中有RedisInputStream和RedisOutputStream兩個(gè)屬性，而發(fā)送命令和獲取返回值都是使用這兩個(gè)成員變量，顯然，這很容易引發(fā)多線(xiàn)程問(wèn)題。測(cè)試代碼如
public class BadConcurrentJedisTest {
private static final ExecutorService pool = Executors.newFixedThreadPool(20);
private static final Jedis jedis = new Jedis("192.168.58.99", 6379);
public static void main(String[] args) {
for(int i=0;i<20;i++){
pool.execute(new RedisSet());
}
}
static class RedisSet implements Runnable{
@Override
public void run() {
while(true){
jedis.set("hello", "world");
}
}
}報(bào)錯(cuò)：
Exception in thread "pool-1-thread-4" redis.clients.jedis.exceptions.JedisConnectionException: java.net.SocketException: Socket Closed
at redis.clients.jedis.Connection.connect(Connection.java:164)
at redis.clients.jedis.BinaryClient.connect(BinaryClient.java:80)
at redis.clients.jedis.Connection.sendCommand(Connection.java:100)
at redis.clients.jedis.BinaryClient.set(BinaryClient.java:97)
at redis.clients.jedis.Client.set(Client.java:32)
at redis.clients.jedis.Jedis.set(Jedis.java:68)
at threadsafe.BadConcurrentJedisTest$RedisSet.run(BadConcurrentJedisTest.java:26)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.net.SocketException: Socket Closed
at java.net.AbstractPlainSocketImpl.setOption(AbstractPlainSocketImpl.java:212)
at java.net.Socket.setKeepAlive(Socket.java:1310)
at redis.clients.jedis.Connection.connect(Connection.java:149)
... 9 more
redis.clients.jedis.exceptions.JedisConnectionException: java.net.SocketException: Socket Closed
at redis.clients.jedis.Connection.connect(Connection.java:164)
at redis.clients.jedis.BinaryClient.connect(BinaryClient.java:80)
at redis.clients.jedis.Connection.sendCommand(Connection.java:100)
at redis.clients.jedis.BinaryClient.set(BinaryClient.java:97)
at redis.clients.jedis.Client.set(Client.java:32)
at redis.clients.jedis.Jedis.set(Jedis.java:68)
at threadsafe.BadConcurrentJedisTest$RedisSet.run(BadConcurrentJedisTest.java:26)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
.......
主要錯(cuò)誤：
ava.net.SocketException: Socket closed
java.net.SocketException: Socket is not connected
2.1 共享socket引起的異常
為什么會(huì)出現(xiàn)這2個(gè)錯(cuò)誤呢？ 我們可以很容易的通過(guò)堆棧信息定位到redis.clients.jedis.Connection的connect方法
public void connect() {
if (!isConnected()) {
try {
socket = new Socket();
// ->@wjw_add
socket.setReuseAddress(true);
socket.setKeepAlive(true); // Will monitor the TCP connection is
// valid
socket.setTcpNoDelay(true); // Socket buffer Whetherclosed, to
// ensure timely delivery of data
socket.setSoLinger(true, 0); // Control calls close () method,
// the underlying socket is closed
// immediately
// <-@wjw_add
socket.connect(new InetSocketAddress(host, port), connectionTimeout);
socket.setSoTimeout(soTimeout);
if (ssl) {
if (null == sslSocketFactory) {
sslSocketFactory = (SSLSocketFactory)SSLSocketFactory.getDefault();
}
socket = (SSLSocket) sslSocketFactory.createSocket(socket, host, port, true);
if (null != sslParameters) {
((SSLSocket) socket).setSSLParameters(sslParameters);
}
if ((null != hostnameVerifier) &&
(!hostnameVerifier.verify(host, ((SSLSocket) socket).getSession()))) {
String message = String.format(
"The connection to '%s' failed ssl/tls hostname verification.", host);
throw new JedisConnectionException(message);
}
}
outputStream = new RedisOutputStream(socket.getOutputStream());
inputStream = new RedisInputStream(socket.getInputStream());
} catch (IOException ex) {
broken = true;
throw new JedisConnectionException(ex);
}
}
}jedis在執(zhí)行每一個(gè)命令之前都會(huì)先執(zhí)行connect方法，socket是一個(gè)共享變量，在多線(xiàn)程的情況下可能存在：線(xiàn)程1執(zhí)行到了
outputStream = new RedisOutputStream(socket.getOutputStream()); inputStream = new RedisInputStream(socket.getInputStream());
線(xiàn)程2執(zhí)行到了：
socket = new Socket(); //線(xiàn)程2 socket.connect(new InetSocketAddress(host, port), connectionTimeout);
因?yàn)榫€(xiàn)程2重新初始化了socket但是還沒(méi)有執(zhí)行connect，所以線(xiàn)程1執(zhí)行socket.getOutputStream()或者socket.getInputStream()就會(huì)拋出java.net.SocketException: Socket is not connected。java.net.SocketException: Socket closed是因?yàn)閟ocket異常導(dǎo)致共享變量socket關(guān)閉了引起的。
2.2 共享數(shù)據(jù)流引起的異常
上面是因?yàn)槎鄠€(gè)線(xiàn)程共享jedis引起的socket異常。除了socket連接引起的異常之外，還有共享數(shù)據(jù)流引起的異常。下面就看一下，因?yàn)楣蚕韏edis實(shí)例引起的共享數(shù)據(jù)流錯(cuò)誤問(wèn)題。
為了避免多線(xiàn)程連接的時(shí)候引起的錯(cuò)誤，我們?cè)诔跏蓟臅r(shí)候就先執(zhí)行一下connect操作：
public class BadConcurrentJedisTest1 {
private static final ExecutorService pool = Executors.newCachedThreadPool();
private static final Jedis jedis = new Jedis("192.168.58.99", 6379);
static{
jedis.connect();
}
public static void main(String[] args) {
for(int i=0;i<20;i++){
pool.execute(new RedisTest());
}
}
static class RedisTest implements Runnable{
@Override
public void run() {
while(true){
jedis.set("hello", "world");
}
}
}
} 報(bào)錯(cuò)：（每次報(bào)的錯(cuò)可能不完全一樣）
Exception in thread "pool-1-thread-7" Exception in thread "pool-1-thread-1" redis.clients.jedis.exceptions.JedisDataException: ERR Protocol error: invalid multibulk length
at redis.clients.jedis.Protocol.processError(Protocol.java:123)
at redis.clients.jedis.Protocol.process(Protocol.java:157)
at redis.clients.jedis.Protocol.read(Protocol.java:211)
at redis.clients.jedis.Connection.readProtocolWithCheckingBroken(Connection.java:297)
at redis.clients.jedis.Connection.getStatusCodeReply(Connection.java:196)
at redis.clients.jedis.Jedis.set(Jedis.java:69)
at threadsafe.BadConcurrentJedisTest1$RedisTest.run(BadConcurrentJedisTest1.java:30)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
Exception in thread "pool-1-thread-4" redis.clients.jedis.exceptions.JedisConnectionException: java.net.SocketException: Broken pipe (Write failed)
at redis.clients.jedis.Connection.flush(Connection.java:291)
at redis.clients.jedis.Connection.getStatusCodeReply(Connection.java:194)
at redis.clients.jedis.Jedis.set(Jedis.java:69)
at threadsafe.BadConcurrentJedisTest1$RedisTest.run(BadConcurrentJedisTest1.java:30)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.net.SocketException: Broken pipe (Write failed)
Protocol error: invalid multibulk lengt是因?yàn)槎嗑€(xiàn)程通過(guò)RedisInputStream和RedisOutputStream讀寫(xiě)緩沖區(qū)的時(shí)候引起的問(wèn)題造成的數(shù)據(jù)問(wèn)題不滿(mǎn)足RESP協(xié)議引起的。舉個(gè)簡(jiǎn)單的例子，例如多個(gè)線(xiàn)程執(zhí)行命令,線(xiàn)程1執(zhí)行 set hello world命令。本來(lái)應(yīng)該發(fā)送：
*3\r\n$3\r\nSET\r\n$5\r\nhello\r\n$5\r\nworld\r\n
但是線(xiàn)程執(zhí)行寫(xiě)到
*3\r\n$3\r\nSET\r\n$5\r\nhello\r\n
然后被掛起了，線(xiàn)程2執(zhí)行了寫(xiě)操作寫(xiě)入了' '，然后線(xiàn)程1繼續(xù)執(zhí)行，最后發(fā)送到redis服務(wù)器端的數(shù)據(jù)可能就是：
*3\r\n$3\r\nSET\r\n$5\r\nhello\r\n' '$5\r\nworld\r\n
至于java.net.SocketException: Connection reset或ReadTimeout錯(cuò)誤，是因?yàn)閞edis服務(wù)器接受到錯(cuò)誤的命令，執(zhí)行了socket.close這樣的操作，關(guān)閉了連接。服務(wù)器會(huì)返回復(fù)位標(biāo)志"RST"，但是客戶(hù)端還在繼續(xù)執(zhí)行讀寫(xiě)數(shù)據(jù)操作。
3、jedis多線(xiàn)程操作
jedis本身不是多線(xiàn)程安全的，這并不是jedis的bug，而是jedis的設(shè)計(jì)與redis本身就是單線(xiàn)程相關(guān)，jedis實(shí)例抽象的是發(fā)送命令相關(guān)，一個(gè)jedis實(shí)例使用一個(gè)線(xiàn)程與使用100個(gè)線(xiàn)程去發(fā)送命令沒(méi)有本質(zhì)上的區(qū)別，所以沒(méi)必要設(shè)置為線(xiàn)程安全的。但是如果需要用多線(xiàn)程方式訪(fǎng)問(wèn)redis服務(wù)器怎么做呢？那就使用多個(gè)jedis實(shí)例，每個(gè)線(xiàn)程對(duì)應(yīng)一個(gè)jedis實(shí)例，而不是一個(gè)jedis實(shí)例多個(gè)線(xiàn)程共享。一個(gè)jedis關(guān)聯(lián)一個(gè)Client，相當(dāng)于一個(gè)客戶(hù)端，Client繼承了Connection，Connection維護(hù)了Socket連接，對(duì)于Socket這種昂貴的連接，一般都會(huì)做池化，jedis提供了JedisPool。
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import redis.clients.jedis.Jedis;
import redis.clients.jedis.JedisPool;
public class JedisPoolTest {
private static final ExecutorService pool = Executors.newCachedThreadPool();
private static final CountDownLatch latch = new CountDownLatch(20);
private static final JedisPool jPool = new JedisPool("192.168.58.99", 6379);
public static void main(String[] args) {
long start = System.currentTimeMillis();
for(int i=0;i<20;i++){
pool.execute(new RedisTest());
}
try {
latch.await();
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(System.currentTimeMillis() - start);
pool.shutdownNow();
}
static class RedisTest implements Runnable{
@Override
public void run() {
Jedis jedis = jPool.getResource();
int i = 1000;
try{
while(i-->0){
jedis.set("hello", "world");
}
}finally{
jedis.close();
latch.countDown();
}
}
}
}到此這篇關(guān)于使用Jedis面臨的非線(xiàn)程安全問(wèn)題詳解的文章就介紹到這了,更多相關(guān)Jedis非線(xiàn)程安全問(wèn)題內(nèi)容請(qǐng)搜索腳本之家以前的文章或繼續(xù)瀏覽下面的相關(guān)文章希望大家以后多多支持腳本之家！
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