高CPU业务
Gearman是当年LiveJournal用来做图片resize的，大家也明白图片resize是一个高CPU的操作，如果让web网站去做这个高CPU的功能，有可能会拖垮你的
web应用，那本篇我们来看看gearman是如何解决这个问题的，它的架构图类似下面这样：
从上面这张图，你应该会看到，Gearman是由三个部分组成：
1. Job Server
这个就是Gearman的Job Server，通过它对Client 和 jobwork 进行桥接，是不是想起来了中介者模式。。。
2. Client
Gearman提供了Client API 给客户端调用，Client只需要将一个高CPU的业务函数名丢给Job Server，然后等待JobServer的返回执行结果。
3. jobwork
Gearman提供了work API 给work客户端进行调用。jobserver会根据后端的work集群的负载情况，分发给一个合适的work去执行，并等待结果。
说到这里，你应该就明白了，本质上它属于那种分布式的RPC调用，而且非常牛逼的地方在于Client 和 Work 可以用不同的语言实现。
一：安装部署
1. 下载地址：https://github.com/gearman/gearmand/releases
目前gearman的JobServer 有C，JAVA，Perl三种语言实现，由于C版本的JobServer是最活跃的，所以这里采用目前最新的1.1.17版本的gearmand在CentOS
上进行安装部署。
2. 快速安装
可以通过官网http://gearman.org/getting-started/中的getting-started进行快速安装。
<1> 基础依赖库安装和gearmand下载
1 yum -y install boost-devel gperf libevent-devel libuuid-devel gcc44 gcc-c++
2 wget https://github.com/gearman/gearmand/releases/download/1.1.17/gearmand-1.1.17.tar.gz
3 cd gearmand-1.1.17.tar.gz
4 tar xzvf gearmand-1.1.17.tar.gz
5 cd gearmand-1.1.17
6 [root@localhost gearmand-1.1.17]# ls
7 aclocal.m4 build-aux configure.ac gear_config.in libgearman-1.0 libhashkit-1.0 Makefile.am rpm THANKS
8 AUTHORS ChangeLog COPYING gearmand libgearmancore libhostile Makefile.in scripts util
9 benchmark configmake.h docs HACKING libgearman-server libtest man support version.m4
10 bin configure examples libgearman libhashkit m4 NEWS tests
<2> 然后就是常规的./configure --prefix=/usr/myapp/gearman && make && make install 这个过程超级慢，可以出去抽跟烟，
顺便再去拉泡屎。。。
1 ./configure --prefix=/usr/myapp/gearman && make && make install
<3> 若干年后，当你看到这个就算安装成功了。。。还是得恭喜一下。。。。至少没让你踩到缺少各种依赖包的界面。
1 See any operating system documentation about shared libraries for
2 more information, such as the ld(1) and ld.so(8) manual pages.
3 ----------------------------------------------------------------------
4 /usr/bin/mkdir -p '/usr/myapp/gearman/sbin'
5 /usr/bin/install -c -m 644 man/gearman_worker_create.3 man/gearman_worker_define_function.3 man/gearman_worker_echo.3 man/gearman_worker_errno.3 man/gearman_worker_error.3 man/gearman_worker_free.3 man/gearman_worker_function_exist.3 man/gearman_worker_grab_job.3 man/gearman_worker_options.3 man/gearman_worker_register.3 man/gearman_worker_remove_options.3 man/gearman_worker_remove_servers.3 man/gearman_worker_set_context.3 man/gearman_worker_set_log_fn.3 man/gearman_worker_set_namespace.3 man/gearman_worker_set_options.3 man/gearman_worker_set_timeout.3 man/gearman_client_has_option.3 man/gearman_client_options_t.3 man/gearman_task_attr_init.3 man/gearman_task_attr_init_background.3 man/gearman_task_attr_init_epoch.3 man/gearman_task_attr_t.3 man/gearman_worker_set_identifier.3 man/gearman_worker_set_workload_free_fn.3 man/gearman_worker_set_workload_malloc_fn.3 man/gearman_worker_st.3 man/gearman_worker_timeout.3 man/gearman_worker_unregister.3 man/gearman_worker_unregister_all.3 man/gearman_worker_wait.3 man/gearman_worker_work.3 man/libgearman.3 '/usr/myapp/gearman/share/man/man3'
6 /bin/sh ./libtool --mode=install /usr/bin/install -c gearmand/gearmand '/usr/myapp/gearman/sbin'
7 libtool: install: /usr/bin/install -c gearmand/gearmand /usr/myapp/gearman/sbin/gearmand
8 /usr/bin/mkdir -p '/usr/myapp/gearman/bin'
9 /bin/sh ./libtool --mode=install /usr/bin/install -c bin/gearman bin/gearadmin '/usr/myapp/gearman/bin'
10 libtool: install: /usr/bin/install -c bin/.libs/gearman /usr/myapp/gearman/bin/gearman
11 libtool: install: /usr/bin/install -c bin/gearadmin /usr/myapp/gearman/bin/gearadmin
12 make[3]: Leaving directory `/usr/myapp/gearmand-1.1.17'
13 make[2]: Leaving directory `/usr/myapp/gearmand-1.1.17'
14 make[1]: Leaving directory `/usr/myapp/gearmand-1.1.17'
<4> 启动gearmand，你也可以用 -d 开启后台运行的模式，这里加上DEBUG只是看一下实时的DEBUG信息，如下所示：
1 [root@localhost myapp]# cd /usr/myapp/gearman
2 [root@localhost gearman]# ls
3 bin include lib sbin share
4 [root@localhost gearman]# cd bin
5 [root@localhost bin]# ls
6 gearadmin gearman
7 [root@localhost bin]# cd /usr/myapp/gearman
8 [root@localhost gearman]# cd sbin
9 [root@localhost sbin]# ls
10 gearmand
11 [root@localhost sbin]# ./gearmand --verbose DEBUG
12 ./gearmand: Could not open log file "/usr/myapp/gearman/var/log/gearmand.log", from "/usr/myapp/gearman/sbin", switching to stderr. (No such file or directory)
13 DEBUG 2017-08-29 02:31:10.796259 [ main ] THREADS: 4 -> libgearman-server/gearmand.cc:263
14 INFO 2017-08-29 02:31:10.796374 [ main ] Initializing Gear on port 4730 with SSL: false
15 INFO 2017-08-29 02:31:10.796487 [ main ] Starting up with pid 40299, verbose is set to DEBUG
16 DEBUG 2017-08-29 02:31:10.796637 [ main ] Method for libevent: epoll -> libgearman-server/gearmand.cc:364
17 DEBUG 2017-08-29 02:31:10.798874 [ main ] Trying to listen on 0.0.0.0:4730 -> libgearman-server/gearmand.cc:646
18 INFO 2017-08-29 02:31:10.800151 [ main ] Listening on 0.0.0.0:4730 (8)
19 DEBUG 2017-08-29 02:31:10.800175 [ main ] Trying to listen on :::4730 -> libgearman-server/gearmand.cc:646
20 INFO 2017-08-29 02:31:10.800307 [ main ] Listening on :::4730 (9)
21 DEBUG 2017-08-29 02:31:10.800333 [ main ] Creating wakeup pipe -> libgearman-server/gearmand.cc:915
22 DEBUG 2017-08-29 02:31:10.800344 [ main ] Creating 4 threads -> libgearman-server/gearmand.cc:378
23 DEBUG 2017-08-29 02:31:10.800357 [ main ] Initializing libevent for IO thread -> libgearman-server/gearmand_thread.cc:224
24 DEBUG 2017-08-29 02:31:10.800406 [ main ] Creating IO thread wakeup pipe -> libgearman-server/gearmand_thread.cc:495
25 DEBUG 2017-08-29 02:31:10.800467 [ main ] Thread 1 created -> libgearman-server/gearmand_thread.cc:273
26 DEBUG 2017-08-29 02:31:10.800507 [ main ] Initializing libevent for IO thread -> libgearman-server/gearmand_thread.cc:224
27 DEBUG 2017-08-29 02:31:10.800550 [ main ] Creating IO thread wakeup pipe -> libgearman-server/gearmand_thread.cc:495
28 DEBUG 2017-08-29 02:31:10.800585 [ main ] Thread 2 created -> libgearman-server/gearmand_thread.cc:273
29 DEBUG 2017-08-29 02:31:10.800594 [ main ] Initializing libevent for IO thread -> libgearman-server/gearmand_thread.cc:224
30 DEBUG 2017-08-29 02:31:10.800632 [ main ] Creating IO thread wakeup pipe -> libgearman-server/gearmand_thread.cc:495
31 DEBUG 2017-08-29 02:31:10.800669 [ main ] Thread 3 created -> libgearman-server/gearmand_thread.cc:273
32 DEBUG 2017-08-29 02:31:10.800677 [ main ] Initializing libevent for IO thread -> libgearman-server/gearmand_thread.cc:224
33 DEBUG 2017-08-29 02:31:10.800714 [ main ] Creating IO thread wakeup pipe -> libgearman-server/gearmand_thread.cc:495
34 DEBUG 2017-08-29 02:31:10.800753 [ main ] Thread 4 created -> libgearman-server/gearmand_thread.cc:273
35 DEBUG 2017-08-29 02:31:10.800761 [ main ] replaying queue: begin -> libgearman-server/gearmand.cc:391
36 DEBUG 2017-08-29 02:31:10.800766 [ main ] __replay -> libgearman-server/plugins/queue/default/queue.cc:101
37 DEBUG 2017-08-29 02:31:10.800774 [ main ] replaying queue: end -> libgearman-server/gearmand.cc:397
38 INFO 2017-08-29 02:31:10.800780 [ main ] Adding event for listening socket (8)
39 INFO 2017-08-29 02:31:10.800787 [ main ] Adding event for listening socket (9)
40 DEBUG 2017-08-29 02:31:10.800794 [ main ] Adding event for wakeup pipe -> libgearman-server/gearmand.cc:966
41 DEBUG 2017-08-29 02:31:10.800801 [ main ] Entering main event loop -> libgearman-server/gearmand.cc:406
42 DEBUG 2017-08-29 02:31:10.801186 [ 2 ] Entering thread event loop -> libgearman-server/gearmand_thread.cc:463
43 DEBUG 2017-08-29 02:31:10.801277 [ 3 ] Entering thread event loop -> libgearman-server/gearmand_thread.cc:463
44 DEBUG 2017-08-29 02:31:10.801507 [ main ] staring up Epoch thread -> libgearman-server/timer.cc:61
45 DEBUG 2017-08-29 02:31:10.801635 [ 1 ] Entering thread event loop -> libgearman-server/gearmand_thread.cc:463
46 DEBUG 2017-08-29 02:31:10.802426 [ 4 ] Entering thread event loop -> libgearman-server/gearmand_thread.cc:463
<5> 最后通过netstat，lsof, ps -ef 三板斧可以找出来gearmand大概占用的端口号，就如你看到的默认占用的4370端口，
当然你也可以在启动的时候用help命令也是能够知道的。
1 [root@localhost ~]# netstat -tln
2 Active Internet connections (only servers)
3 Proto Recv-Q Send-Q Local Address Foreign Address State
4 tcp 0 0 192.168.122.1:53 0.0.0.0:* LISTEN
5 tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN
6 tcp 0 0 127.0.0.1:631 0.0.0.0:* LISTEN
7 tcp 0 0 127.0.0.1:25 0.0.0.0:* LISTEN
8 tcp 0 0 0.0.0.0:4730 0.0.0.0:* LISTEN
9 tcp6 0 0 :::8009 :::* LISTEN
10 tcp6 0 0 :::8080 :::* LISTEN
11 tcp6 0 0 :::22 :::* LISTEN
12 tcp6 0 0 ::1:631 :::* LISTEN
13 tcp6 0 0 ::1:25 :::* LISTEN
14 tcp6 0 0 :::4730 :::* LISTEN
15 tcp6 0 0 127.0.0.1:8005 :::* LISTEN
16 [root@localhost ~]# ps -ef | grep gearmand
17 root 40299 15869 0 02:31 pts/1 00:00:00 ./gearmand --verbose DEBUG
18 root 40364 40327 0 02:33 pts/2 00:00:00 grep --color=auto gearmand
19 [root@localhost ~]# lsof -i :4730
20 COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
21 gearmand 40299 root 8u IPv4 322550 0t0 TCP *:gearman (LISTEN)
22 gearmand 40299 root 9u IPv6 322551 0t0 TCP *:gearman (LISTEN)
23 [root@localhost ~]#
二：Java Driver 在 Gearman上的使用
为了演示，我可以做一个简单的 “字符串.ToUpper”的业务逻辑来验证一下这个架构是否可以跑的起来。
1. java 充当 Gearman 的 work
首先需要在mvn仓库中拉一下jar包：http://www.mvnrepository.com/artifact/org.gearman/gearman-java/0.6。
<1> UpperFunction类，这个类用于定义work具体的业务逻辑：
1 package com.datamip.gearmanwork;
2
3 import java.text.SimpleDateFormat;
4 import java.util.Date;
5
6 import org.gearman.client.GearmanJobResult;
7 import org.gearman.client.GearmanJobResultImpl;
8 import org.gearman.util.ByteUtils;
9 import org.gearman.worker.AbstractGearmanFunction;
10
11 //字符串大写的业务Function
12 public class UpperFunction extends AbstractGearmanFunction {
13
14 @Override
15 public GearmanJobResult executeFunction() {
16
17 String param = ByteUtils.fromUTF8Bytes((byte[]) this.data);
18
19 byte[] mybytes = param.toUpperCase().getBytes();
20
21 GearmanJobResultImpl result = new GearmanJobResultImpl(mybytes, true, mybytes, null, null, -1, -1);
22
23 SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
24
25 String dateString = formatter.format(new Date());
26
27 System.out.println(String.format("当前时间:%s, 过来的字符串:%s，返回的字符串:%s", dateString, param,new String(mybytes)));
28
29 return result;
30 }
31 }
<2> 将UpperFunction注册到gearmand中，从红色代码可以看到，其实是一个kv模式，这里的key="myUpperFunc”的对应执行业务就是new UpperFunction。
这样Client只需要传递一个"myUpperFunc"，Gearmand就知道这个“字符串”对应是哪一个处理函数。。。
1 public class App {
2 public static void main(String[] args) {
3
4 GearmanWorker worker = new GearmanWorkerImpl();
5
6 GearmanNIOJobServerConnection conn = new GearmanNIOJobServerConnection("192.168.23.170", 4730);
7 worker.addServer(conn);
8
9 // 将‘将转大写的函数注册’ 到gearmand中
10 worker.registerFunctionFactory(new GearmanFunctionFactory() {
11
12 public String getFunctionName() {
13 return "myUpperFunc";
14 }
15
16 public GearmanFunction getFunction() {
17 return new UpperFunction();
18 }
19 });
20
21 System.out.println("启动服务。。。。");
22
23 worker.work();
24 }
25 }2. java 充当 Gearman 的 client
<1> GearSubmit类【简单的一个包装类，随便定义】
1 package com.datamip.gearmanclient;
2
3 import java.util.concurrent.ExecutionException;
4 import java.util.concurrent.ExecutorService;
5 import java.util.concurrent.Executors;
6 import java.util.concurrent.Future;
7
8 import org.gearman.client.GearmanClient;
9 import org.gearman.client.GearmanClientImpl;
10 import org.gearman.client.GearmanJob;
11 import org.gearman.client.GearmanJobImpl;
12 import org.gearman.client.GearmanJobResult;
13 import org.gearman.common.GearmanJobServerConnection;
14 import org.gearman.common.GearmanNIOJobServerConnection;
15 import org.gearman.util.ByteUtils;
16
17 public class Gearsubmit {
18
19 public void process() throws InterruptedException, ExecutionException {
20
21 GearmanJobServerConnection conn = new GearmanNIOJobServerConnection("192.168.23.170", 4730);
22
23 GearmanClient client = new GearmanClientImpl();
24
25 client.addJobServer(conn); // 添加连接
26
27 String functionName = "myUpperFunc";
28
29 byte[] data = ByteUtils.toUTF8Bytes("hello,world");
30
31 // 创建后台任务
32 GearmanJob job = GearmanJobImpl.createJob(functionName, data, null);
33
34 GearmanJobResult jobResult = null;
35
36 Future<GearmanJobResult> gearmanJobResult = client.submit(job);
37
38 jobResult = gearmanJobResult.get();
39
40 byte[] resultBytes = jobResult.getResults();
41
42 // 获取job的返回值
43 String value = ByteUtils.fromUTF8Bytes(resultBytes);
44
45 System.out.println(value);
46
47 System.out.println("执行结束");
48
49 client.shutdown();
50 }
51 }
<2> 主程序，开多线程并发的去执行。
1 public class App {
2 public static void main(String[] args) throws InterruptedException, ExecutionException, IOException {
3
4 ExecutorService executorService = Executors.newFixedThreadPool(100);
5
6 for (int i = 0; i < 10000; i++) {
7 executorService.execute(new Runnable() {
8
9 @Override
10 public void run() {
11 Gearsubmit submit=new Gearsubmit();
12
13 try {
14 submit.process();
15 } catch (InterruptedException | ExecutionException e) {
16 // TODO Auto-generated catch block
17 e.printStackTrace();
18 }
19 }
20 });
21 }
22
23 System.in.read();
24 }
25 }好了，一切都准备好了，接下来为了演示，演示就是解释，我用Jar2Exe把work程序导出成jar再转换成exe，如下图：
然后我把3.exe开成5个实例，client用100个线程的线程池并发调用，当然一切都是模拟。。。。可以看到，当我client启动的时候，5个work都在执行，
如果这个时候，你把某一个work停止了，jobserver也不再将任务丢给它，而是转给其他负载相对小的work继续执行。
好了，本篇就说到这里，希望对你有帮助。