Redis：解决分布式高并发修改同一个Key的问题
Redis：解决分布式高并发修改同一个Key的问题
本篇文章是通过watch（监控）+mutil（事务）实现应用于在分布式高并发处理等相关场景。下边先通过redis-cli.exe来测试多个线程修改时，遇到问题及解决问题。
高并发下修改同一个key遇到的问题：
1）定义一个hash类型的key，key为：lock_test，元素locker的值初始化为0。
2）实现高并发下对locker元素的值递增：定义64个多线程，并发的对lock_test元素locker的值进行修改。
package com.dx.es;import java.util.concurrent.CountDownLatch;
import redis.clients.jedis.Jedis;
import redis.clients.jedis.JedisPool;public class Test_UnLock {
public static void main(String[] args) {
final JedisPool pool = RedisUtil.getPool();</span><span style="color: #008000;">//</span><span style="color: #008000;"> 获得jedis对象</span> Jedis jedis =<span style="color: #000000;"> pool.getResource(); jedis.hset(</span>"lock_test", "locker", "0"<span style="color: #000000;">); String val </span>= jedis.hget("lock_test", "locker"<span style="color: #000000;">); System.out.println(</span>"lock_test.locker的初始值為：" +<span style="color: #000000;"> val); jedis.close(); </span><span style="color: #0000ff;">int</span> threahSize = 64<span style="color: #000000;">; </span><span style="color: #0000ff;">final</span> CountDownLatch threadsCountDownLatch = <span style="color: #0000ff;">new</span><span style="color: #000000;"> CountDownLatch(threahSize); Runnable handler </span>= <span style="color: #0000ff;">new</span><span style="color: #000000;"> Runnable() { </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> run() { Jedis jedis </span>=<span style="color: #000000;"> pool.getResource(); Integer integer </span>= Integer.valueOf(jedis.hget("lock_test", "locker"<span style="color: #000000;">)); jedis.hset(</span>"lock_test", "locker", String.valueOf(integer + 1<span style="color: #000000;">)); jedis.close(); threadsCountDownLatch.countDown(); } }; </span><span style="color: #0000ff;">for</span> (<span style="color: #0000ff;">int</span> i = 0; i < threahSize; i++<span style="color: #000000;">) { </span><span style="color: #0000ff;">new</span><span style="color: #000000;"> Thread(handler).start(); } </span><span style="color: #008000;">//</span><span style="color: #008000;"> 等待所有并行子线程任务完成。</span> <span style="color: #0000ff;">try</span><span style="color: #000000;"> { threadsCountDownLatch.await(); } </span><span style="color: #0000ff;">catch</span><span style="color: #000000;"> (InterruptedException e) { e.printStackTrace(); } System.out.println(</span>"complete"<span style="color: #000000;">); val </span>= jedis.hget("lock_test", "locker"<span style="color: #000000;">); System.out.println(val); }}
RedisUtil.java
package com.dx.es;import redis.clients.jedis.JedisPool;
import redis.clients.jedis.JedisPoolConfig;public class RedisUtil {
public static JedisPool getPool() {
// 简单创建 Jedis的方法：
// final Jedis jedis = new Jedis("127.0.0.1",6379);</span><span style="color: #008000;">//</span><span style="color: #008000;"> 下边使用线程池的方案：jedis对象是线程不安全的，因此在并发情况下要使用JedisPool,默认情况下jedisPool只支持8个连接，因此在声明JedisPool时要先修改JedisPool的最大连接数</span> JedisPoolConfig config = <span style="color: #0000ff;">new</span><span style="color: #000000;"> JedisPoolConfig(); </span><span style="color: #008000;">//</span><span style="color: #008000;"> 修改最大连接数</span> config.setMaxTotal(32<span style="color: #000000;">); </span><span style="color: #008000;">//</span><span style="color: #008000;"> 声明一个线程池</span> JedisPool pool = <span style="color: #0000ff;">new</span> JedisPool(config, "127.0.0.1", 6379<span style="color: #000000;">); </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> pool; }}
此时，会出现以下问题：
- A线程获取key的值为0，而B线程也获取jkey的值0，则A把key值递增为1，B线程也实现把key值递增为1。两个线程都执行了key值修改：0到1。
- 在1）中最终key修改为了1，但是c线程获取key的值为0（因为c线程读取key值时，a、b线程还未触发修改，因此c线程读取到的值为0），此时d线程读取到的值为1（因为d线程读取key值时，a、b线程已触发修改，一次d线程取到的值为1）。
- 此时假设d线程优先触发递增，则在c线程未触发提交之前d线程已经把值修改了2，但是c此时并不知道在它获取到值到修改之前这段时间发生了什么，直接把值修改1。
此时执行打印结果为：
lock_test.locker的初始值為：0 complete 24 #备注：也可能是其他值，可能是正确值64的可能性比较小。
通过watch+mutil解决并发修改的问题：
需要掌握Redis 事务命令：
下表列出了 redis 事务的相关命令：
| 序号 | 命令 | 描述 | 可用版本 |
| 1 | DISCARD |
Redis Discard 命令用于取消事务，放弃执行事务块内的所有命令。 语法 redis Discard 命令基本语法如下： redis 127.0.0.1:6379> DISCARD |
>= 2.0.0 |
| 2 | EXEC |
Redis Exec 命令用于执行所有事务块内的命令。 语法 redis Exec 命令基本语法如下： redis 127.0.0.1:6379>Exec |
>= 1.2.0 |
| 3 | MULTI |
Redis Multi 命令用于标记一个事务块的开始。 事务块内的多条命令会按照先后顺序被放进一个队列当中，最后由 EXEC 命令原子性(atomic)地执行。 语法 redis Multi 命令基本语法如下： redis 127.0.0.1:6379>Multi |
>= 1.2.0 |
| 4 | UNWATCH |
Redis Unwatch 命令用于取消 WATCH 命令对所有 key 的监视。 语法 redis Unwatch 命令基本语法如下： redis 127.0.0.1:6379> UNWATCH |
>= 2.2.0 |
| 5 | WATCH |
Redis Watch 命令用于监视一个(或多个) key ，如果在事务执行之前这个(或这些) key 被其他命令所改动，那么事务将被打断 语法 redis Watch 命令基本语法如下： WATCH key [key ...] |
>= 2.2.0 |
Redis 事务可以一次执行多个命令， 并且带有以下两个重要的保证：
- 批量操作在发送 EXEC 命令前被放入队列缓存。
- 收到 EXEC 命令后进入事务执行，事务中任意命令执行失败，其余的命令依然被执行。
- 在事务执行过程，其他客户端提交的命令请求不会插入到事务执行命令序列中。
一个事务从开始到执行会经历以下三个阶段：
- 开始事务。
- 命令入队。
- 执行事务。
备注：概念性摘自《http://www.runoob.com/redis/redis-transactions.html》
redis-cli.exe下的事务操作：
# 事务被成功执行
redis 127.0.0.1:6379> MULTI
OK
redis 127.0.0.1:6379> INCR user_id
QUEUED
redis 127.0.0.1:6379> INCR user_id
QUEUED
redis 127.0.0.1:6379> INCR user_id
QUEUED
redis 127.0.0.1:6379> PING
QUEUED
redis 127.0.0.1:6379> EXEC
1) (integer) 1
2) (integer) 2
3) (integer) 3
4) PONG
并发情况下使用watch+mutil操作：
事务块内所有命令的返回值，按命令执行的先后顺序排列。 当操作被打断时，返回空值 nil 。
A线程：
# 监视 key ，且事务成功执行
redis 127.0.0.1:6379> WATCH lock lock_times
OK
redis 127.0.0.1:6379> MULTI
OK
redis 127.0.0.1:6379> SET lock "huangz"
QUEUED
redis 127.0.0.1:6379> INCR lock_times
QUEUED
redis 127.0.0.1:6379> EXEC
1) OK
2) (integer) 1
B线程：
# 监视 key ，且事务被打断
redis 127.0.0.1:6379> WATCH lock lock_times
OK
redis 127.0.0.1:6379> MULTI
OK
redis 127.0.0.1:6379> SET lock "joe" # 就在这时，另一个客户端修改了 lock_times 的值
QUEUED
redis 127.0.0.1:6379> INCR lock_times
QUEUED
redis 127.0.0.1:6379> EXEC # 因为 lock_times 被修改， joe 的事务执行失败
(nil)
上边演示了A、B线程并发下的watch+mutil操作情况。
解决高并发下修改同一个key遇到的问题：
package com.dx.es;import java.util.List;
import java.util.concurrent.CountDownLatch;import redis.clients.jedis.Jedis;
import redis.clients.jedis.JedisPool;
import redis.clients.jedis.Transaction;public class Test_Lock3 {
public static void main(String[] args) {
final JedisPool pool = RedisUtil.getPool();</span><span style="color: #008000;">//</span><span style="color: #008000;"> 对测试key赋初始值</span> Jedis jedis =<span style="color: #000000;"> pool.getResource(); jedis.hset(</span>"lock_test", "locker", "0"<span style="color: #000000;">); String val </span>= jedis.hget("lock_test", "locker"<span style="color: #000000;">); System.out.println(</span>"lock_test.locker的初始值為：" +<span style="color: #000000;"> val); jedis.close(); </span><span style="color: #0000ff;">int</span> threahSize = 64<span style="color: #000000;">; </span><span style="color: #0000ff;">final</span> CountDownLatch threadsCountDownLatch = <span style="color: #0000ff;">new</span><span style="color: #000000;"> CountDownLatch(threahSize); Runnable handler </span>= <span style="color: #0000ff;">new</span><span style="color: #000000;"> Runnable() { </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> run() { Jedis jedis </span>=<span style="color: #000000;"> pool.getResource(); </span><span style="color: #0000ff;">while</span> (<span style="color: #0000ff;">true</span><span style="color: #000000;">) { jedis.watch(</span>"lock_test"<span style="color: #000000;">); String val </span>= jedis.hget("lock_test", "locker"<span style="color: #000000;">); Integer integer </span>=<span style="color: #000000;"> Integer.valueOf(val); Transaction tx </span>=<span style="color: #000000;"> jedis.multi(); tx.hset(</span>"lock_test", "locker", String.valueOf(integer + 1<span style="color: #000000;">)); List</span><Object> exec =<span style="color: #000000;"> tx.exec(); </span><span style="color: #0000ff;">if</span> (exec == <span style="color: #0000ff;">null</span> ||<span style="color: #000000;"> exec.isEmpty()) { System.out.println(Thread.currentThread().getName() </span>+ ":" + "Error:(" + val + "=>" + (integer + 1) + ")"<span style="color: #000000;">); } </span><span style="color: #0000ff;">else</span><span style="color: #000000;"> { String values </span>= ""<span style="color: #000000;">; </span><span style="color: #0000ff;">for</span> (<span style="color: #0000ff;">int</span> i = 0; i < exec.size(); i++<span style="color: #000000;">) { values </span>+=<span style="color: #000000;"> exec.get(i).toString(); } System.out.println(Thread.currentThread().getName() </span>+ ":" + values + ":(" + val + "=>" + (integer + 1) + ")"<span style="color: #000000;">); </span><span style="color: #0000ff;">break</span><span style="color: #000000;">; } </span><span style="color: #0000ff;">try</span><span style="color: #000000;"> { Thread.sleep(</span>10<span style="color: #000000;">); } </span><span style="color: #0000ff;">catch</span><span style="color: #000000;"> (InterruptedException e) { e.printStackTrace(); } } jedis.close(); threadsCountDownLatch.countDown(); } }; </span><span style="color: #0000ff;">for</span> (<span style="color: #0000ff;">int</span> i = 0; i < threahSize; i++<span style="color: #000000;">) { </span><span style="color: #0000ff;">new</span><span style="color: #000000;"> Thread(handler).start(); } </span><span style="color: #008000;">//</span><span style="color: #008000;"> 等待所有并行子线程任务完成。</span> <span style="color: #0000ff;">try</span><span style="color: #000000;"> { threadsCountDownLatch.await(); } </span><span style="color: #0000ff;">catch</span><span style="color: #000000;"> (InterruptedException e) { e.printStackTrace(); } System.out.println(</span>"complete"<span style="color: #000000;">); val </span>= jedis.hget("lock_test", "locker"<span style="color: #000000;">); System.out.println(val); }}
打印结果：
lock_test.locker的初始值為：0 Thread-8:0:(0=>1) Thread-56:Error:(1=>2) Thread-53:0:(1=>2) Thread-25:Error:(0=>1) Thread-18:Error:(0=>1) Thread-3:Error:(0=>1) Thread-30:Error:(2=>3) Thread-11:Error:(2=>3) Thread-9:Error:(0=>1) Thread-63:0:(2=>3) Thread-7:Error:(0=>1) Thread-10:0:(3=>4) Thread-34:0:(4=>5) Thread-65:Error:(4=>5) Thread-24:Error:(0=>1) Thread-17:Error:(0=>1) Thread-62:0:(5=>6) Thread-29:Error:(6=>7) Thread-61:0:(6=>7) Thread-64:0:(7=>8) Thread-16:Error:(0=>1) Thread-19:Error:(8=>9) Thread-6:Error:(0=>1) Thread-28:Error:(0=>1) Thread-21:Error:(0=>1) Thread-14:Error:(0=>1) Thread-20:Error:(0=>1) Thread-5:Error:(0=>1) Thread-13:Error:(0=>1) Thread-15:Error:(0=>1) Thread-22:Error:(0=>1) Thread-4:Error:(0=>1) Thread-12:Error:(0=>1) Thread-23:Error:(0=>1) Thread-54:Error:(0=>1) Thread-57:Error:(0=>1) Thread-26:0:(8=>9) Thread-27:Error:(8=>9) Thread-32:Error:(9=>10) Thread-35:Error:(9=>10) Thread-56:0:(9=>10) Thread-33:Error:(10=>11) Thread-50:0:(10=>11) Thread-31:0:(11=>12) Thread-38:0:(12=>13) Thread-25:Error:(13=>14) Thread-36:0:(13=>14) Thread-39:Error:(14=>15) Thread-14:0:(14=>15) Thread-19:Error:(14=>15) Thread-17:Error:(14=>15) Thread-6:Error:(14=>15) Thread-9:Error:(14=>15) Thread-33:Error:(14=>15) Thread-35:Error:(14=>15) Thread-23:Error:(14=>15) Thread-18:Error:(14=>15) Thread-15:Error:(14=>15) Thread-11:Error:(14=>15) Thread-7:Error:(14=>15) Thread-57:Error:(14=>15) Thread-27:Error:(14=>15) Thread-16:Error:(14=>15) Thread-65:Error:(14=>15) Thread-24:Error:(14=>15) Thread-13:Error:(14=>15) Thread-32:Error:(15=>16) Thread-28:Error:(14=>15) Thread-21:Error:(14=>15) Thread-30:Error:(14=>15) Thread-54:Error:(14=>15) Thread-22:Error:(14=>15) Thread-25:Error:(14=>15) Thread-3:Error:(14=>15) Thread-29:Error:(14=>15) Thread-5:Error:(14=>15) Thread-12:Error:(14=>15) Thread-20:Error:(14=>15) Thread-40:0:(15=>16) Thread-4:Error:(14=>15) Thread-41:0:(16=>17) Thread-44:0:(17=>18) Thread-45:0:(18=>19) Thread-47:0:(19=>20) Thread-43:0:(20=>21) Thread-48:0:(21=>22) Thread-37:0:(22=>23) Thread-49:0:(23=>24) Thread-55:0:(24=>25) Thread-60:0:(25=>26) Thread-42:0:(26=>27) Thread-52:0:(27=>28) Thread-46:0:(28=>29) Thread-58:0:(29=>30) Thread-51:0:(30=>31) Thread-66:0:(31=>32) Thread-59:0:(32=>33) Thread-17:0:(33=>34) Thread-19:Error:(33=>34) Thread-39:Error:(33=>34) Thread-28:0:(34=>35) Thread-54:Error:(34=>35) Thread-65:Error:(34=>35) Thread-25:Error:(34=>35) Thread-30:Error:(34=>35) Thread-5:Error:(35=>36) Thread-13:Error:(35=>36) Thread-16:Error:(34=>35) Thread-6:Error:(34=>35) Thread-9:Error:(34=>35) Thread-21:Error:(35=>36) Thread-29:Error:(35=>36) Thread-33:Error:(34=>35) Thread-57:Error:(35=>36) Thread-24:Error:(34=>35) Thread-22:Error:(34=>35) Thread-32:Error:(35=>36) Thread-23:Error:(34=>35) Thread-7:Error:(34=>35) Thread-15:Error:(34=>35) Thread-4:0:(35=>36) Thread-20:Error:(35=>36) Thread-12:Error:(35=>36) Thread-35:0:(36=>37) Thread-18:Error:(36=>37) Thread-11:Error:(36=>37) Thread-3:Error:(36=>37) Thread-27:Error:(37=>38) Thread-39:Error:(37=>38) Thread-19:0:(37=>38) Thread-7:Error:(38=>39) Thread-33:0:(38=>39) Thread-29:Error:(38=>39) Thread-16:Error:(38=>39) Thread-22:Error:(38=>39) Thread-65:Error:(38=>39) Thread-54:Error:(38=>39) Thread-57:Error:(38=>39) Thread-30:Error:(38=>39) Thread-21:Error:(38=>39) Thread-24:Error:(38=>39) Thread-32:Error:(39=>40) Thread-5:Error:(39=>40) Thread-13:Error:(39=>40) Thread-6:Error:(38=>39) Thread-25:Error:(38=>39) Thread-9:Error:(38=>39) Thread-20:0:(39=>40) Thread-12:Error:(39=>40) Thread-15:Error:(38=>39) Thread-23:Error:(38=>39) Thread-18:Error:(40=>41) Thread-3:Error:(40=>41) Thread-27:0:(40=>41) Thread-11:Error:(40=>41) Thread-39:0:(41=>42) Thread-7:Error:(42=>43) Thread-54:0:(42=>43) Thread-22:Error:(42=>43) Thread-30:Error:(42=>43) Thread-57:Error:(42=>43) Thread-65:Error:(42=>43) Thread-32:Error:(43=>44) Thread-24:Error:(43=>44) Thread-5:Error:(42=>43) Thread-21:Error:(42=>43) Thread-16:Error:(43=>44) Thread-29:Error:(43=>44) Thread-6:0:(43=>44) Thread-9:Error:(43=>44) Thread-23:Error:(43=>44) Thread-25:Error:(43=>44) Thread-15:Error:(43=>44) Thread-12:Error:(43=>44) Thread-13:Error:(44=>45) Thread-11:0:(44=>45) Thread-18:Error:(44=>45) Thread-3:Error:(44=>45) Thread-57:0:(45=>46) Thread-7:Error:(45=>46) Thread-22:Error:(45=>46) Thread-30:Error:(45=>46) Thread-9:0:(46=>47) Thread-65:Error:(46=>47) Thread-25:Error:(46=>47) Thread-24:Error:(46=>47) Thread-21:Error:(47=>48) Thread-32:Error:(47=>48) Thread-5:Error:(47=>48) Thread-15:Error:(47=>48) Thread-16:0:(47=>48) Thread-29:Error:(47=>48) Thread-12:Error:(48=>49) Thread-23:Error:(47=>48) Thread-13:0:(48=>49) Thread-18:Error:(49=>50) Thread-3:Error:(49=>50) Thread-7:0:(49=>50) Thread-30:Error:(49=>50) Thread-22:Error:(49=>50) Thread-25:0:(50=>51) Thread-65:Error:(50=>51) Thread-12:0:(51=>52) Thread-21:Error:(51=>52) Thread-32:Error:(52=>53) Thread-24:Error:(52=>53) Thread-29:Error:(52=>53) Thread-5:Error:(52=>53) Thread-23:Error:(52=>53) Thread-15:Error:(52=>53) Thread-18:0:(52=>53) Thread-3:Error:(52=>53) Thread-30:0:(53=>54) Thread-22:Error:(53=>54) Thread-65:0:(54=>55) Thread-24:0:(55=>56) Thread-21:Error:(55=>56) Thread-32:Error:(55=>56) Thread-5:0:(56=>57) Thread-29:Error:(57=>58) Thread-15:0:(57=>58) Thread-23:Error:(57=>58) Thread-3:0:(58=>59) Thread-22:0:(59=>60) Thread-32:0:(60=>61) Thread-21:Error:(60=>61) Thread-29:0:(61=>62) Thread-23:Error:(61=>62) Thread-21:0:(62=>63) Thread-23:0:(63=>64) complete 64
备注：实际应用场景中我这里不是实现自增，上边代码自增目的：测试是否能够在高并发下修改同一个key时实现锁的功能。
实际应用：高并发使用redis同一个key存储统计TOPN结果
需求：
1）拥有多个记录，每条记录数据格式：日期，统计指标1，统计指标2，统计指标3，统计指标4
2）要求分别统计出4个指标的最大值，并记录各自指标最大值时对应的记录。
3）记录中各个字段的模拟公式：
// 数据格式: // 第一列：日期 // 第二列：f(x) = x*0.7+1(x自然数) 最大值 45.1 // 第三列：f（x）= -x*x+20x+1(自然数) a=-1,b=20,c=1 ， 当x=-b/2a时 y 最大值：-10*10+20*10+1=101 // 第四列：f（x）= -x*x+30x+1(自然数) a=-1,b=30,c=1 ， 当x=-b/2a时 y 最大值：-15*15+30*15+1=445-225+1=221 // 第五列：f（x）= 640/(x+1)(x自然数) 最大值 640
使用mutil+watch实现：
首先，把最终统计结果存储到redis的key（lock_test）中，lock_test是一个hash类型，其中存储四个键值对，每个键值对分别存储各自的指标最大值时对应的记录。
指标配置项存储到FeildConfig.java
static class FieldConfig { private String key; private Integer index;</span><span style="color: #0000ff;">public</span><span style="color: #000000;"> String getKey() { </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> key; } </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> setKey(String key) { </span><span style="color: #0000ff;">this</span>.key =<span style="color: #000000;"> key; } </span><span style="color: #0000ff;">public</span><span style="color: #000000;"> Integer getIndex() { </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> index; } </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> setIndex(Integer index) { </span><span style="color: #0000ff;">this</span>.index =<span style="color: #000000;"> index; } </span><span style="color: #0000ff;">public</span><span style="color: #000000;"> FieldConfig(String key, Integer index) { </span><span style="color: #0000ff;">super</span><span style="color: #000000;">(); </span><span style="color: #0000ff;">this</span>.key =<span style="color: #000000;"> key; </span><span style="color: #0000ff;">this</span>.index =<span style="color: #000000;"> index; } }</span></pre>
在测试类的static构造函数中初始化各自指标在一条记录的中索引位置，及一共包含的指标类型：
public class Test_Lock3 { 。。。 final static List<FieldConfig> keys = new ArrayList<FieldConfig>();</span><span style="color: #0000ff;">static</span><span style="color: #000000;"> { keys.add(</span><span style="color: #0000ff;">new</span> FieldConfig("101", 1<span style="color: #000000;">)); keys.add(</span><span style="color: #0000ff;">new</span> FieldConfig("102", 2<span style="color: #000000;">)); keys.add(</span><span style="color: #0000ff;">new</span> FieldConfig("103", 3<span style="color: #000000;">)); keys.add(</span><span style="color: #0000ff;">new</span> FieldConfig("104", 4<span style="color: #000000;">)); } 。。。}
备注：101代表指标1，对应在被统计记录中的第1索引位置（备注：这里索引是对记录按照“,”分割后的数组索引位置）。
制作测试数据：
List<String> dataItems=new ArrayList<String>();</span><span style="color: #008000;">//</span><span style="color: #008000;"> 数据格式: </span><span style="color: #008000;">//</span><span style="color: #008000;"> 第一列：日期 </span><span style="color: #008000;">//</span><span style="color: #008000;"> 第二列：f(x) = x*0.7+1(x自然数) 最大值 45.1 </span><span style="color: #008000;">//</span><span style="color: #008000;"> 第三列：f（x）= -x*x+20x+1(自然数) a=-1,b=20,c=1 ， 当x=-b/2a时 y 最大值：-10*10+20*10+1=101 </span><span style="color: #008000;">//</span><span style="color: #008000;"> 第四列：f（x）= -x*x+30x+1(自然数) a=-1,b=30,c=1 ， 当x=-b/2a时 y 最大值：-15*15+30*15+1=445-225+1=221 </span><span style="color: #008000;">//</span><span style="color: #008000;"> 第五列：f（x）= 640/(x+1)(x自然数) 最大值 640 </span> <span style="color: #0000ff;">for</span>(<span style="color: #0000ff;">int</span> x=0;x<threahSize;x++<span style="color: #000000;">){ String dataItem </span>= "2018-07-29 00:00:00," + (x*0.7d+1) + "," + (-1d*x*x+20*x+1) + "," + (-1d*x*x+30*x+1) + "," + (640d/(x+1<span style="color: #000000;">)); dataItems.add(dataItem); }</span></pre>
以下是整体测试代码：
package com.dx.es;import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.concurrent.CountDownLatch;import redis.clients.jedis.Jedis;
import redis.clients.jedis.JedisPool;
import redis.clients.jedis.Transaction;public class Test_Lock3 {
final static JedisPool pool = RedisUtil.getPool();
final static List<FieldConfig> keys = new ArrayList<FieldConfig>();</span><span style="color: #0000ff;">static</span><span style="color: #000000;"> { keys.add(</span><span style="color: #0000ff;">new</span> FieldConfig("101", 1<span style="color: #000000;">)); keys.add(</span><span style="color: #0000ff;">new</span> FieldConfig("102", 2<span style="color: #000000;">)); keys.add(</span><span style="color: #0000ff;">new</span> FieldConfig("103", 3<span style="color: #000000;">)); keys.add(</span><span style="color: #0000ff;">new</span> FieldConfig("104", 4<span style="color: #000000;">)); } </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> main(String[] args) { </span><span style="color: #0000ff;">int</span> threahSize = 64<span style="color: #000000;">; </span><span style="color: #0000ff;">final</span> CountDownLatch threadsCountDownLatch = <span style="color: #0000ff;">new</span><span style="color: #000000;"> CountDownLatch(threahSize); Jedis jedis </span>=<span style="color: #000000;"> pool.getResource(); jedis.del(</span>"lock_test"<span style="color: #000000;">); List</span><String> dataItems=<span style="color: #0000ff;">new</span> ArrayList<String><span style="color: #000000;">(); </span><span style="color: #008000;">//</span><span style="color: #008000;"> 数据格式: </span><span style="color: #008000;">//</span><span style="color: #008000;"> 第一列：日期 </span><span style="color: #008000;">//</span><span style="color: #008000;"> 第二列：f(x) = x*0.7+1(x自然数) 最大值 45.1 </span><span style="color: #008000;">//</span><span style="color: #008000;"> 第三列：f（x）= -x*x+20x+1(自然数) a=-1,b=20,c=1 ， 当x=-b/2a时 y 最大值：-10*10+20*10+1=101 </span><span style="color: #008000;">//</span><span style="color: #008000;"> 第四列：f（x）= -x*x+30x+1(自然数) a=-1,b=30,c=1 ， 当x=-b/2a时 y 最大值：-15*15+30*15+1=445-225+1=221 </span><span style="color: #008000;">//</span><span style="color: #008000;"> 第五列：f（x）= 640/(x+1)(x自然数) 最大值 640 </span> <span style="color: #0000ff;">for</span>(<span style="color: #0000ff;">int</span> x=0;x<threahSize;x++<span style="color: #000000;">){ String dataItem </span>= "2018-07-29 00:00:00," + (x*0.7d+1) + "," + (-1d*x*x+20*x+1) + "," + (-1d*x*x+30*x+1) + "," + (640d/(x+1<span style="color: #000000;">)); dataItems.add(dataItem); } </span><span style="color: #0000ff;">for</span> (<span style="color: #0000ff;">int</span> i = 0; i < threahSize; i++<span style="color: #000000;">) { Jedis jedisT </span>=<span style="color: #000000;"> pool.getResource(); Runnable handler </span>= <span style="color: #0000ff;">new</span><span style="color: #000000;"> MyRunable(jedisT, threadsCountDownLatch, dataItems.get(i)); </span><span style="color: #0000ff;">new</span><span style="color: #000000;"> Thread(handler).start(); } </span><span style="color: #008000;">//</span><span style="color: #008000;"> 等待所有并行子线程任务完成。</span> <span style="color: #0000ff;">try</span><span style="color: #000000;"> { threadsCountDownLatch.await(); } </span><span style="color: #0000ff;">catch</span><span style="color: #000000;"> (InterruptedException e) { e.printStackTrace(); } System.out.println(</span>"complete"<span style="color: #000000;">); Map</span><String, String> values = jedis.hgetAll("lock_test"<span style="color: #000000;">); jedis.close(); System.out.println(values); } </span><span style="color: #0000ff;">static</span> <span style="color: #0000ff;">class</span> MyRunable <span style="color: #0000ff;">implements</span><span style="color: #000000;"> Runnable { </span><span style="color: #0000ff;">private</span> Jedis jedis = <span style="color: #0000ff;">null</span><span style="color: #000000;">; </span><span style="color: #0000ff;">private</span> CountDownLatch threadsCountDownLatch = <span style="color: #0000ff;">null</span><span style="color: #000000;">; </span><span style="color: #0000ff;">private</span> String newLine = <span style="color: #0000ff;">null</span><span style="color: #000000;">; </span><span style="color: #0000ff;">public</span><span style="color: #000000;"> MyRunable(Jedis jedis, CountDownLatch threadsCountDownLatch, String newLine) { </span><span style="color: #0000ff;">this</span>.jedis =<span style="color: #000000;"> jedis; </span><span style="color: #0000ff;">this</span>.threadsCountDownLatch =<span style="color: #000000;"> threadsCountDownLatch; </span><span style="color: #0000ff;">this</span>.newLine =<span style="color: #000000;"> newLine; } </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> run() { </span><span style="color: #0000ff;">while</span> (<span style="color: #0000ff;">true</span><span style="color: #000000;">) { </span><span style="color: #0000ff;">this</span>.jedis.watch("lock_test"<span style="color: #000000;">); Map</span><String, String> newValues = <span style="color: #0000ff;">new</span> HashMap<String, String><span style="color: #000000;">(); Map</span><String, String> oldValues = <span style="color: #0000ff;">this</span>.jedis.hgetAll("lock_test"<span style="color: #000000;">); String newValueStr</span>=""<span style="color: #000000;">; </span><span style="color: #0000ff;">for</span><span style="color: #000000;"> (FieldConfig key : keys) { </span><span style="color: #0000ff;">if</span><span style="color: #000000;"> (oldValues.containsKey(key.getKey())) { Double oldValue </span>= Double.valueOf(oldValues.get(key.getKey()).split(","<span style="color: #000000;">)[key.getIndex()]); Double newValue </span>= Double.valueOf(newLine.split(","<span style="color: #000000;">)[key.getIndex()]); </span><span style="color: #0000ff;">if</span> (newValue ><span style="color: #000000;"> oldValue) { newValues.put(key.getKey(), newLine); newValueStr</span>=<span style="color: #000000;">newLine; } </span><span style="color: #0000ff;">else</span><span style="color: #000000;"> { newValues.put(key.getKey(), oldValues.get(key.getKey())); newValueStr</span>=<span style="color: #000000;">oldValues.get(key.getKey()); } } </span><span style="color: #0000ff;">else</span><span style="color: #000000;"> { newValues.put(key.getKey(), newLine); newValueStr</span>=<span style="color: #000000;">newLine; } } Transaction tx </span>= <span style="color: #0000ff;">this</span><span style="color: #000000;">.jedis.multi(); tx.hmset(</span>"lock_test"<span style="color: #000000;">, newValues); List</span><Object> exec =<span style="color: #000000;"> tx.exec(); </span><span style="color: #0000ff;">if</span> (exec == <span style="color: #0000ff;">null</span> ||<span style="color: #000000;"> exec.isEmpty()) { </span><span style="color: #008000;">//</span><span style="color: #008000;">System.out.println(Thread.currentThread().getName() + ":" + "Error:(" + oldValueStr + "->"+newValueStr+")");</span> } <span style="color: #0000ff;">else</span><span style="color: #000000;"> { String values </span>= ""<span style="color: #000000;">; </span><span style="color: #0000ff;">for</span> (<span style="color: #0000ff;">int</span> i = 0; i < exec.size(); i++<span style="color: #000000;">) { values </span>+=<span style="color: #000000;"> exec.get(i).toString(); } System.out.println(Thread.currentThread().getName() </span>+ ":" + values + ":(" + newLine +"->"+newValueStr+")"<span style="color: #000000;">); </span><span style="color: #0000ff;">break</span><span style="color: #000000;">; } </span><span style="color: #0000ff;">try</span><span style="color: #000000;"> { Thread.sleep(</span>10<span style="color: #000000;">); } </span><span style="color: #0000ff;">catch</span><span style="color: #000000;"> (InterruptedException e) { e.printStackTrace(); } } </span><span style="color: #0000ff;">this</span><span style="color: #000000;">.jedis.close(); </span><span style="color: #0000ff;">this</span><span style="color: #000000;">.threadsCountDownLatch.countDown(); } } </span><span style="color: #0000ff;">static</span> <span style="color: #0000ff;">class</span><span style="color: #000000;"> FieldConfig { </span><span style="color: #0000ff;">private</span><span style="color: #000000;"> String key; </span><span style="color: #0000ff;">private</span><span style="color: #000000;"> Integer index; </span><span style="color: #0000ff;">public</span><span style="color: #000000;"> String getKey() { </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> key; } </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> setKey(String key) { </span><span style="color: #0000ff;">this</span>.key =<span style="color: #000000;"> key; } </span><span style="color: #0000ff;">public</span><span style="color: #000000;"> Integer getIndex() { </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> index; } </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> setIndex(Integer index) { </span><span style="color: #0000ff;">this</span>.index =<span style="color: #000000;"> index; } </span><span style="color: #0000ff;">public</span><span style="color: #000000;"> FieldConfig(String key, Integer index) { </span><span style="color: #0000ff;">super</span><span style="color: #000000;">(); </span><span style="color: #0000ff;">this</span>.key =<span style="color: #000000;"> key; </span><span style="color: #0000ff;">this</span>.index =<span style="color: #000000;"> index; } }}
测试：
Thread-23:OK:(2018-07-29 00:00:00,15.0,1.0,201.0,30.476190476190474->2018-07-29 00:00:00,15.0,1.0,201.0,30.476190476190474) Thread-29:OK:(2018-07-29 00:00:00,19.2,-155.0,105.0,23.703703703703702->2018-07-29 00:00:00,15.0,1.0,201.0,30.476190476190474) Thread-33:OK:(2018-07-29 00:00:00,22.0,-299.0,1.0,20.64516129032258->2018-07-29 00:00:00,15.0,1.0,201.0,30.476190476190474) Thread-24:OK:(2018-07-29 00:00:00,15.7,-20.0,190.0,29.09090909090909->2018-07-29 00:00:00,15.0,1.0,201.0,30.476190476190474) Thread-36:OK:(2018-07-29 00:00:00,24.099999999999998,-428.0,-98.0,18.823529411764707->2018-07-29 00:00:00,15.0,1.0,201.0,30.476190476190474) Thread-32:OK:(2018-07-29 00:00:00,21.299999999999997,-260.0,30.0,21.333333333333332->2018-07-29 00:00:00,15.0,1.0,201.0,30.476190476190474) Thread-39:OK:(2018-07-29 00:00:00,26.2,-575.0,-215.0,17.2972972972973->2018-07-29 00:00:00,15.0,1.0,201.0,30.476190476190474) Thread-40:OK:(2018-07-29 00:00:00,26.9,-628.0,-258.0,16.842105263157894->2018-07-29 00:00:00,15.0,1.0,201.0,30.476190476190474) Thread-25:OK:(2018-07-29 00:00:00,16.4,-43.0,177.0,27.82608695652174->2018-07-29 00:00:00,15.0,1.0,201.0,30.476190476190474) Thread-3:OK:(2018-07-29 00:00:00,1.0,1.0,1.0,640.0->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-16:OK:(2018-07-29 00:00:00,10.1,92.0,222.0,45.714285714285715->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-21:OK:(2018-07-29 00:00:00,13.6,37.0,217.0,33.68421052631579->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-45:OK:(2018-07-29 00:00:00,30.4,-923.0,-503.0,14.883720930232558->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-28:OK:(2018-07-29 00:00:00,18.5,-124.0,126.0,24.615384615384617->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-46:OK:(2018-07-29 00:00:00,31.099999999999998,-988.0,-558.0,14.545454545454545->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-12:OK:(2018-07-29 00:00:00,7.3,100.0,190.0,64.0->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-34:OK:(2018-07-29 00:00:00,22.7,-340.0,-30.0,20.0->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-49:OK:(2018-07-29 00:00:00,33.199999999999996,-1195.0,-735.0,13.617021276595745->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-50:OK:(2018-07-29 00:00:00,33.9,-1268.0,-798.0,13.333333333333334->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-52:OK:(2018-07-29 00:00:00,35.3,-1420.0,-930.0,12.8->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-53:OK:(2018-07-29 00:00:00,36.0,-1499.0,-999.0,12.549019607843137->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-54:OK:(2018-07-29 00:00:00,36.699999999999996,-1580.0,-1070.0,12.307692307692308->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-55:OK:(2018-07-29 00:00:00,37.4,-1663.0,-1143.0,12.075471698113208->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-56:OK:(2018-07-29 00:00:00,38.099999999999994,-1748.0,-1218.0,11.851851851851851->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-57:OK:(2018-07-29 00:00:00,38.8,-1835.0,-1295.0,11.636363636363637->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-58:OK:(2018-07-29 00:00:00,39.5,-1924.0,-1374.0,11.428571428571429->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-59:OK:(2018-07-29 00:00:00,40.199999999999996,-2015.0,-1455.0,11.228070175438596->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-60:OK:(2018-07-29 00:00:00,40.9,-2108.0,-1538.0,11.03448275862069->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-61:OK:(2018-07-29 00:00:00,41.599999999999994,-2203.0,-1623.0,10.847457627118644->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-62:OK:(2018-07-29 00:00:00,42.3,-2300.0,-1710.0,10.666666666666666->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-63:OK:(2018-07-29 00:00:00,43.0,-2399.0,-1799.0,10.491803278688524->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-64:OK:(2018-07-29 00:00:00,43.699999999999996,-2500.0,-1890.0,10.32258064516129->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-65:OK:(2018-07-29 00:00:00,44.4,-2603.0,-1983.0,10.158730158730158->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-11:OK:(2018-07-29 00:00:00,6.6,97.0,177.0,71.11111111111111->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-41:OK:(2018-07-29 00:00:00,27.599999999999998,-683.0,-303.0,16.41025641025641->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-47:OK:(2018-07-29 00:00:00,31.799999999999997,-1055.0,-615.0,14.222222222222221->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-37:OK:(2018-07-29 00:00:00,24.799999999999997,-475.0,-135.0,18.285714285714285->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-48:OK:(2018-07-29 00:00:00,32.5,-1124.0,-674.0,13.91304347826087->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-5:OK:(2018-07-29 00:00:00,2.4,37.0,57.0,213.33333333333334->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-42:OK:(2018-07-29 00:00:00,28.299999999999997,-740.0,-350.0,16.0->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-8:OK:(2018-07-29 00:00:00,4.5,76.0,126.0,106.66666666666667->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-9:OK:(2018-07-29 00:00:00,5.199999999999999,85.0,145.0,91.42857142857143->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-43:OK:(2018-07-29 00:00:00,29.0,-799.0,-399.0,15.609756097560975->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-7:OK:(2018-07-29 00:00:00,3.8,65.0,105.0,128.0->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-44:OK:(2018-07-29 00:00:00,29.7,-860.0,-450.0,15.238095238095237->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-18:OK:(2018-07-29 00:00:00,11.5,76.0,226.0,40.0->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-20:OK:(2018-07-29 00:00:00,12.899999999999999,52.0,222.0,35.55555555555556->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-15:OK:(2018-07-29 00:00:00,9.399999999999999,97.0,217.0,49.23076923076923->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-27:OK:(2018-07-29 00:00:00,17.799999999999997,-95.0,145.0,25.6->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-17:OK:(2018-07-29 00:00:00,10.799999999999999,85.0,225.0,42.666666666666664->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-10:OK:(2018-07-29 00:00:00,5.8999999999999995,92.0,162.0,80.0->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-66:OK:(2018-07-29 00:00:00,45.099999999999994,-2708.0,-2078.0,10.0->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-19:OK:(2018-07-29 00:00:00,12.2,65.0,225.0,37.64705882352941->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-26:OK:(2018-07-29 00:00:00,17.099999999999998,-68.0,162.0,26.666666666666668->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-4:OK:(2018-07-29 00:00:00,1.7,20.0,30.0,320.0->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-35:OK:(2018-07-29 00:00:00,23.4,-383.0,-63.0,19.393939393939394->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-22:OK:(2018-07-29 00:00:00,14.299999999999999,20.0,210.0,32.0->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-31:OK:(2018-07-29 00:00:00,20.599999999999998,-223.0,57.0,22.06896551724138->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-51:OK:(2018-07-29 00:00:00,34.599999999999994,-1343.0,-863.0,13.061224489795919->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-30:OK:(2018-07-29 00:00:00,19.9,-188.0,82.0,22.857142857142858->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-6:OK:(2018-07-29 00:00:00,3.0999999999999996,52.0,82.0,160.0->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-14:OK:(2018-07-29 00:00:00,8.7,100.0,210.0,53.333333333333336->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-13:OK:(2018-07-29 00:00:00,8.0,101.0,201.0,58.18181818181818->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) Thread-38:OK:(2018-07-29 00:00:00,25.5,-524.0,-174.0,17.77777777777778->2018-07-29 00:00:00,1.0,1.0,1.0,640.0) complete {
101=2018-07-29 00:00:00,45.099999999999994,-2708.0,-2078.0,10.0,
102=2018-07-29 00:00:00,8.0,101.0,201.0,58.18181818181818,
103=2018-07-29 00:00:00,11.5,76.0,226.0,40.0,
104=2018-07-29 00:00:00,1.0,1.0,1.0,640.0
}
参考：《通过Jedis的setnx、multi事务及watch实现三种分布式跨JVM锁的方法代码示例》注意：本章文章中介绍了三种锁的方案，但是这三种方案并不能解决topn的问题，仅供参考。
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1）List/Set/Map内部组成原理|区别
2）mysql索引存储结构&如何调优/b-tree特点、计算复杂度及影响复杂度的因素。。。
3）JVM运行组成与原理及调优
4）Java类加载器运行原理
5）Java中GC过程原理|使用的回收算法原理
6）Redis中hash一致性实现及与hash其他区别
7）Java多线程、线程池开发、管理Lock与Synchroined区别
8）Spring IOC/AOP 原理；加载过程的。。。
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<div class="postDesc">posted @ <span id="post-date">2018-07-29 13:33</span> <a href="https://www.cnblogs.com/yy3b2007com/">cctext</a> 阅读(<span id="post_view_count">4255</span>) 评论(<span id="post_comment_count">0</span>) <a href="https://i.cnblogs.com/EditPosts.aspx?postid=9383713" rel="nofollow">编辑</a> <a href="#" onclick="AddToWz(9383713);return false;">收藏</a></div>
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