jedis是一個著名的key-value存儲系統，而作為其官方推薦的java版客戶端jedis也非常強大和穩定，支持事務、管道及有jedis自身實現的分布式。

在這里對jedis關于事務、管道和分布式的調用方式做一個簡單的介紹和對比：

一、普通同步方式

最簡單和基礎的調用方式，

@Test

public void test1Normal() {

Jedis jedis = new Jedis("localhost");

long start = System.currentTimeMillis();

for (int i = 0; i < 100000; i++) {

String result = jedis.set("n" + i, "n" + i);

}

long end = System.currentTimeMillis();

System.out.println("Simple SET: " + ((end - start)/1000.0) + " seconds");

jedis.disconnect();

}

很簡單吧，每次set之后都可以返回結果，標記是否成功。

二、事務方式(Transactions)

redis的事務很簡單，他主要目的是保障，一個client發起的事務中的命令可以連續的執行，而中間不會插入其他client的命令。

看下面例子：

@Test

public void test2Trans() {

Jedis jedis = new Jedis("localhost");

long start = System.currentTimeMillis();

Transaction tx = jedis.multi();

for (int i = 0; i < 100000; i++) {

tx.set("t" + i, "t" + i);

}

List results = tx.exec();

long end = System.currentTimeMillis();

System.out.println("Transaction SET: " + ((end - start)/1000.0) + " seconds");

jedis.disconnect();

}

我們調用jedis.watch(…)方法來監控key，如果調用后key值發生變化，則整個事務會執行失敗。另外，事務中某個操作失敗，并不會回滾其他操作。這一點需要注意。還有，我們可以使用discard()方法來取消事務。

三、管道(Pipelining)

有時，我們需要采用異步方式，一次發送多個指令，不同步等待其返回結果。這樣可以取得非常好的執行效率。這就是管道，調用方法如下：

@Test

public void test3Pipelined() {

Jedis jedis = new Jedis("localhost");

Pipeline pipeline = jedis.pipelined();

long start = System.currentTimeMillis();

for (int i = 0; i < 100000; i++) {

pipeline.set("p" + i, "p" + i);

}

List results = pipeline.syncAndReturnAll();

long end = System.currentTimeMillis();

System.out.println("Pipelined SET: " + ((end - start)/1000.0) + " seconds");

jedis.disconnect();

}

四、管道中調用事務

就Jedis提供的方法而言，是可以做到在管道中使用事務，其代碼如下：

@Test

public void test4combPipelineTrans() {

jedis = new Jedis("localhost");

long start = System.currentTimeMillis();

Pipeline pipeline = jedis.pipelined();

pipeline.multi();

for (int i = 0; i < 100000; i++) {

pipeline.set("" + i, "" + i);

}

pipeline.exec();

List results = pipeline.syncAndReturnAll();

long end = System.currentTimeMillis();

System.out.println("Pipelined transaction: " + ((end - start)/1000.0) + " seconds");

jedis.disconnect();

}

但是經測試(見本文后續部分)，發現其效率和單獨使用事務差不多，甚至還略微差點。

五、分布式直連同步調用

@Test

public void test5shardNormal() {

List shards = Arrays.asList(

new JedisShardInfo("localhost",6379),

new JedisShardInfo("localhost",6380));

ShardedJedis sharding = new ShardedJedis(shards);

long start = System.currentTimeMillis();

for (int i = 0; i < 100000; i++) {

String result = sharding.set("sn" + i, "n" + i);

}

long end = System.currentTimeMillis();

System.out.println("

[email?protected] SET: " + ((end - start)/1000.0) + " seconds");

sharding.disconnect();

}

這個是分布式直接連接，并且是同步調用，每步執行都返回執行結果。類似地，還有異步管道調用。

六、分布式直連異步調用

@Test

public void test6shardpipelined() {

List shards = Arrays.asList(

new JedisShardInfo("localhost",6379),

new JedisShardInfo("localhost",6380));

ShardedJedis sharding = new ShardedJedis(shards);

ShardedJedisPipeline pipeline = sharding.pipelined();

long start = System.currentTimeMillis();

for (int i = 0; i < 100000; i++) {

pipeline.set("sp" + i, "p" + i);

}

List results = pipeline.syncAndReturnAll();

long end = System.currentTimeMillis();

System.out.println("

[email?protected] SET: " + ((end - start)/1000.0) + " seconds");

sharding.disconnect();

}

七、分布式連接池同步調用

如果，你的分布式調用代碼是運行在線程中，那么上面兩個直連調用方式就不合適了，因為直連方式是非線程安全的，這個時候，你就必須選擇連接池調用。

@Test

public void test7shardSimplePool() {

List shards = Arrays.asList(

new JedisShardInfo("localhost",6379),

new JedisShardInfo("localhost",6380));

ShardedJedisPool pool = new ShardedJedisPool(new JedisPoolConfig(), shards);

ShardedJedis one = pool.getResource();

long start = System.currentTimeMillis();

for (int i = 0; i < 100000; i++) {

String result = one.set("spn" + i, "n" + i);

}

long end = System.currentTimeMillis();

pool.returnResource(one);

System.out.println("

[email?protected] SET: " + ((end - start)/1000.0) + " seconds");

pool.destroy();

}

上面是同步方式，當然還有異步方式。

八、分布式連接池異步調用

@Test

public void test8shardPipelinedPool() {

List shards = Arrays.asList(

new JedisShardInfo("localhost",6379),

new JedisShardInfo("localhost",6380));

ShardedJedisPool pool = new ShardedJedisPool(new JedisPoolConfig(), shards);

ShardedJedis one = pool.getResource();

ShardedJedisPipeline pipeline = one.pipelined();

long start = System.currentTimeMillis();

for (int i = 0; i < 100000; i++) {

pipeline.set("sppn" + i, "n" + i);

}

List results = pipeline.syncAndReturnAll();

long end = System.currentTimeMillis();

pool.returnResource(one);

System.out.println("

[email?protected] SET: " + ((end - start)/1000.0) + " seconds");

pool.destroy();

}

九、需要注意的地方

事務和管道都是異步模式。在事務和管道中不能同步查詢結果。比如下面兩個調用，都是不允許的：

Transaction tx = jedis.multi();

for (int i = 0; i < 100000; i++) {

tx.set("t" + i, "t" + i);

}

System.out.println(tx.get("t1000").get());? //不允許

List results = tx.exec();

Pipeline pipeline = jedis.pipelined();

long start = System.currentTimeMillis();

for (int i = 0; i < 100000; i++) {

pipeline.set("p" + i, "p" + i);

}

System.out.println(pipeline.get("p1000").get()); //不允許

List results = pipeline.syncAndReturnAll();

事務和管道都是異步的，個人感覺，在管道中再進行事務調用，沒有必要，不如直接進行事務模式。

分布式中，連接池的性能比直連的性能略好(見后續測試部分)。

分布式調用中不支持事務。

因為事務是在服務器端實現，而在分布式中，每批次的調用對象都可能訪問不同的機器，所以，沒法進行事務。

十、測試

運行上面的代碼，進行測試，其結果如下：

Simple SET: 5.227 seconds

Transaction SET: 0.5 seconds

Pipelined SET: 0.353 seconds

Pipelined transaction: 0.509 seconds

[email?protected] SET: 5.289 seconds

[email?protected] SET: 0.348 seconds

[email?protected] SET: 5.039 seconds

[email?protected] SET: 0.401 seconds

另外，經測試分布式中用到的機器越多，調用會越慢。上面是2片，下面是5片：

[email?protected] SET: 5.494 seconds

[email?protected] SET: 0.51 seconds

[email?protected] SET: 5.223 seconds

[email?protected] SET: 0.518 seconds

下面是10片：

[email?protected] SET: 5.9 seconds

[email?protected] SET: 0.794 seconds

[email?protected] SET: 5.624 seconds

[email?protected] SET: 0.762 seconds

下面是100片：

[email?protected] SET: 14.055 seconds

[email?protected] SET: 8.185 seconds

[email?protected] SET: 13.29 seconds

[email?protected] SET: 7.767 seconds

分布式中，連接池方式調用不但線程安全外，根據上面的測試數據，也可以看出連接池比直連的效率更好。

十一、完整的測試代碼

import java.util.Arrays;

import java.util.List;

import org.junit.AfterClass;

import org.junit.BeforeClass;

import org.junit.Test;

import redis.clients.jedis.Jedis;

import redis.clients.jedis.JedisPoolConfig;

import redis.clients.jedis.JedisShardInfo;

import redis.clients.jedis.Pipeline;

import redis.clients.jedis.ShardedJedis;

import redis.clients.jedis.ShardedJedisPipeline;

import redis.clients.jedis.ShardedJedisPool;

import redis.clients.jedis.Transaction;

import org.junit.FixMethodOrder;

import org.junit.runners.MethodSorters;

@FixMethodOrder(MethodSorters.NAME_ASCENDING)

public class TestJedis {

private static Jedis jedis;

private static ShardedJedis sharding;

private static ShardedJedisPool pool;

@BeforeClass

public static void setUpBeforeClass() throws Exception {

List shards = Arrays.asList(

new JedisShardInfo("localhost",6379),

new JedisShardInfo("localhost",6379)); //使用相同的ip:port,僅作測試

jedis = new Jedis("localhost");

sharding = new ShardedJedis(shards);

pool = new ShardedJedisPool(new JedisPoolConfig(), shards);

}

@AfterClass

public static void tearDownAfterClass() throws Exception {

jedis.disconnect();

sharding.disconnect();

pool.destroy();

}

@Test

public void test1Normal() {

long start = System.currentTimeMillis();

for (int i = 0; i < 100000; i++) {

String result = jedis.set("n" + i, "n" + i);

}

long end = System.currentTimeMillis();

System.out.println("Simple SET: " + ((end - start)/1000.0) + " seconds");

}

@Test

public void test2Trans() {

long start = System.currentTimeMillis();

Transaction tx = jedis.multi();

for (int i = 0; i < 100000; i++) {

tx.set("t" + i, "t" + i);

}

//System.out.println(tx.get("t1000").get());

List results = tx.exec();

long end = System.currentTimeMillis();

System.out.println("Transaction SET: " + ((end - start)/1000.0) + " seconds");

}

@Test

public void test3Pipelined() {

Pipeline pipeline = jedis.pipelined();

long start = System.currentTimeMillis();

for (int i = 0; i < 100000; i++) {

pipeline.set("p" + i, "p" + i);

}

//System.out.println(pipeline.get("p1000").get());

List results = pipeline.syncAndReturnAll();

long end = System.currentTimeMillis();

System.out.println("Pipelined SET: " + ((end - start)/1000.0) + " seconds");

}

@Test

public void test4combPipelineTrans() {

long start = System.currentTimeMillis();

Pipeline pipeline = jedis.pipelined();

pipeline.multi();

for (int i = 0; i < 100000; i++) {

pipeline.set("" + i, "" + i);

}

pipeline.exec();

List results = pipeline.syncAndReturnAll();

long end = System.currentTimeMillis();

System.out.println("Pipelined transaction: " + ((end - start)/1000.0) + " seconds");

}

@Test

public void test5shardNormal() {

long start = System.currentTimeMillis();

for (int i = 0; i < 100000; i++) {

String result = sharding.set("sn" + i, "n" + i);

}

long end = System.currentTimeMillis();

System.out.println("

[email?protected] SET: " + ((end - start)/1000.0) + " seconds");

}

@Test

public void test6shardpipelined() {

ShardedJedisPipeline pipeline = sharding.pipelined();

long start = System.currentTimeMillis();

for (int i = 0; i < 100000; i++) {

pipeline.set("sp" + i, "p" + i);

}

List results = pipeline.syncAndReturnAll();

long end = System.currentTimeMillis();

System.out.println("

[email?protected] SET: " + ((end - start)/1000.0) + " seconds");

}

@Test

public void test7shardSimplePool() {

ShardedJedis one = pool.getResource();

long start = System.currentTimeMillis();

for (int i = 0; i < 100000; i++) {

String result = one.set("spn" + i, "n" + i);

}

long end = System.currentTimeMillis();

pool.returnResource(one);

System.out.println("

[email?protected] SET: " + ((end - start)/1000.0) + " seconds");

}

@Test

public void test8shardPipelinedPool() {

ShardedJedis one = pool.getResource();

ShardedJedisPipeline pipeline = one.pipelined();

long start = System.currentTimeMillis();

for (int i = 0; i < 100000; i++) {

pipeline.set("sppn" + i, "n" + i);

}

List results = pipeline.syncAndReturnAll();

long end = System.currentTimeMillis();

pool.returnResource(one);

System.out.println("

[email?protected] SET: " + ((end - start)/1000.0) + " seconds");

}

}

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