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摘自：https://mp.weixin.qq.com/s/nTEkdrHM2bv3aRdj4mEQeg
连接池的种类
其实也就是连接池的使用场景1、可以是一个独立部署的服务，通过套接字提供代理服务。例如我们的常用的mysqlproxy。
2、可以是一个服务内部进程间共享的连接池，这种相对更加轻量，可以理解为项目级别，只对内提供服务。 3、进程内的连接池，更加轻量，当前进程内的线程或者协程可以使用。今天我们这里要介绍的是进程内的连接池，我们以PHP为例，使用协程并发的场景来观察连接池的作用效果。
首先我们要心里琢磨，我们连接池的连接作用： 1、减少客户端使用连接时，创建和销毁连接的时间和系统资源开销，这里涉及到TCP的三次握手也四次挥手，还有TCP的慢启动预热。 2、避免极端情况大量连接直接涌入后端服务，对整个系统服务造成危害。 但同时也有一些缺点，比如空闲状态下也要维护一定数量的连接，占用客户端和服务端的资源，这里可以根据实际需求动态调配连接数，达到效率和资源利用的平衡。哪有一点资源不占用，还想系统高效稳定的事情，建个水坝还得占片地，护坝人间断性的职守呢。例如我们要提供100QPS的服务用户查询服务，后端DB是Redis（也可以是mysql，我们这里只是假设，实际上redis的单机处理能力是10w/s这个数量级）,我可以先事先创建好100个redis连接，每个请求到来拿一个连接使用，请求结束后再归还到连接池中。但是万一有超过预期并发量的连接应该怎么办呢，一般可以排队处理或者降级处理。排队时等待当前服务进程空闲后再处理，当然这会增加客户端的响应时间。降级处理是返回其他的数据，不走DB请求。
下面秀出我们的基础代码，这里只是演示功能，没有对模块做进一步封装。
Step 1 最简单的http服务器 server = $server; } function request($request, $response){ $redis = new redis; $redis->connect("127.0.0.1", 6379); $val = $redis->get("key"); $response->end("Hello Swoole redis val $val #" . rand(1000, 9999) . ""); } function start(){ $this->server->on('request', [$this, "request"]); $this->server->set([ 'worker_num' => 1 ]); $this->server->start(); }}(new MyServer())->start();
我们使用 swoole process 多进程模式，只开启一个进程为方便调试，运行脚本后
$ ps -ef | grep -v grep |grep server1.phpshiguan+ 30587 8251 0 20:37 pts/11 00:00:00 php server1.phpshiguan+ 30588 30587 0 20:37 pts/11 00:00:00 php server1.phpshiguan+ 30590 30588 0 20:37 pts/11 00:00:00 php server1.php
我们可以发现三个进程，熟悉swoole的同学都知道30590进程是工作进程．
我们在命令行执行 curl 'http://127.0.0.1:9501' 可以得到服务器反馈
Hello Swoole redis val value2 #6642
然后我们通过lsof -p 30590 查看工作进程打开的文件描述符, 发现并没有redis的连接．这是为什么呢？自问自答一波，因为在php的执行流程中，所有局部变量在退出当前作用域时，都会进行释放，也就是16行建立连接的$redis对象，在执行完毕当前请求后进行了释放，我们可以通过strace进一步验证
$ sudo strace -s 1000 -p 30590strace: Process 30590 attachedepoll_wait(3, [{ EPOLLIN, { u32=4, u64=12884901892}}], 4096, -1) = 1read(4, "\2\0\0\0N\0\0\0\0\0\0\0\3\0\0\0GET / HTTP/1.1\r\nHost: 127.0.0.1:9501\r\nUser-Agent: curl/7.58.0\r\nAccept: */*\r\n\r\n", 425952) = 94brk(0x55bdabaae000) = 0x55bdabaae000socket(AF_INET, SOCK_STREAM, IPPROTO_IP) = 7fcntl(7, F_GETFL) = 0x2 (flags O_RDWR)fcntl(7, F_SETFL, O_RDWR|O_NONBLOCK) = 0connect(7, { sa_family=AF_INET, sin_port=htons(6379), sin_addr=inet_addr("127.0.0.1")}, 16) = -1 EINPROGRESS (Operation now in progress)poll([{ fd=7, events=POLLIN|POLLOUT|POLLERR|POLLHUP}], 1, 60000) = 1 ([{ fd=7, revents=POLLOUT}])getsockopt(7, SOL_SOCKET, SO_ERROR, [0], [4]) = 0fcntl(7, F_SETFL, O_RDWR) = 0setsockopt(7, SOL_TCP, TCP_NODELAY, [1], 4) = 0setsockopt(7, SOL_SOCKET, SO_KEEPALIVE, [0], 4) = 0poll([{ fd=7, events=POLLIN|POLLPRI|POLLERR|POLLHUP}], 1, 0) = 0 (Timeout)sendto(7, "*2\r\n$3\r\nGET\r\n$3\r\nkey\r\n", 22, MSG_DONTWAIT, NULL, 0) = 22poll([{ fd=7, events=POLLIN|POLLPRI|POLLERR|POLLHUP}], 1, 0) = 0 (Timeout)poll([{ fd=7, events=POLLIN|POLLERR|POLLHUP}], 1, 60000) = 1 ([{ fd=7, revents=POLLIN}])recvfrom(7, "$6\r\nvalue2\r\n", 8192, MSG_DONTWAIT, NULL, NULL) = 12close(7) = 0sendto(4, "\2\0\0\0\305\0\0\0\0\0\0\0\0\0\0\0HTTP/1.1 200 OK\r\nServer: swoole-http-server\r\nConnection: keep-alive\r\nContent-Type: text/html\r\nDate: Tue, 22 Oct 2019 12:43:10 GMT\r\nContent-Length: 44\r\n\r\nHello Swoole redis val value2 #4823", 213, 0, NULL, 0) = 213brk(0x55bdab88e000) = 0x55bdab88e000epoll_wait(3, [{ EPOLLIN, { u32=4, u64=12884901892}}], 4096, -1) = 1read(4, "\2\0\0\0\0\0\0\0\0\0\4\0\3\0\0\0", 425952) = 16sendto(4, "\2\0\0\0\0\0\0\0\0\0\4\0\0\0\0\0", 16, 0, NULL, 0) = 16epoll_wait(3,
我们可以发现连接到redis的fd，在执行完recv以后close(7)关闭了连接．
话外音: 行走江湖重要招式，lsof -p pid, strace -p pid 到这里和连接池没有半毛钱关系，因为这个服务是短连接，每次处理请求需要创建连接，关闭连接，对应有tcp的三次握手和四次挥手等老生长谈的问题，具体可以参考我们郭新华老师在Swoole微课程中的视频教程． Step 2
感受一下长连接,我们可以通过将连接对象的变量赋值给类属性的简单操作，增加其引用计数，从而使得请求结束后不能对对象进行释放． server = $server; } function request($request, $response){ $redis = new redis; $redis->connect("127.0.0.1", 6379); $this->pool[] = $redis; $val = $redis->get("key"); $response->end("Hello Swoole redis val $val #" . rand(1000, 9999) . ""); } function start(){ $this->server->on('request', [$this, "request"]); $this->server->set([ 'worker_num' => 1 ]); $this->server->start(); }}(new MyServer())->start();
通过简单的代码修改，然后通过 lsof -p 查看工作进程打开的文件描述符
…php 31598 shiguangqi 4u unix 0x0000000000000000 0t0 6577793 type=DGRAMphp 31598 shiguangqi 5u unix 0x0000000000000000 0t0 6577794 type=DGRAMphp 31598 shiguangqi 6u a_inode 0,13 0 11932 [signalfd]php 31598 shiguangqi 7u IPv4 6579223 0t0 TCP localhost:48048->localhost:6379 (ESTABLISHED)
我们可以发现在最下方真的有打开的redis连接，同样也可以strace来跟踪请求的系统调用，这里我们省去．这个代码是我们每次请求都去创建新的连接，没有任何复用，基本无法使用．
Step 3
渐入佳境，我们想要的是可以重复利用的一个连接池，有几种选择当请求到来的时候，尝试从连接池中获取连接对象，如果连接池为空，创建连接对象，请求结束的时候，归还至连接池.
进程启动的时候，创建固定数量的连接对象，当请求到来的时候，尝试从连接池中获取连接对象，如果连接池为空，继续等待或者服务降级; 不为空的话正常服务，请求结束的时候，归还至连接池. 我们这里选择第一种方式，每个方式都各有优势，我们可根据自己情况进行取舍，下面是动态创建连接的实例代码 server = $server; $this->pool = new \SplQueue(); } function request($request, $response){ if ($this->pool->count() > 0) { $redis = $this->pool->pop(); } else { $redis = new redis; $redis->connect("127.0.0.1", 6379); } $val = $redis->get("key"); $response->end("Hello Swoole redis val $val #" . rand(1000, 9999) . ""); $this->pool->push($redis); } function start(){ $this->server->on('request', [$this, "request"]); $this->server->set([ 'worker_num' => 1 ]); $this->server->start(); }}(new MyServer())->start();
我们这里实现了连接的动态创建和复用，可以通过strace来验证发现，两次连续的请求，第一次会创建连接，第二次会复用我们的fd
$ sudo strace -s 1000 -p 1001[sudo] shiguangqi 的密码：strace: Process 1001 attachedbrk(0x556c8955b000) = 0x556c8955b000epoll_wait(3, [{ EPOLLIN, { u32=4, u64=12884901892}}], 4096, -1) = 1read(4, "\1\0\0\0N\0\0\0\0\0\0\0\3\0\0\0GET / HTTP/1.1\r\nHost: 127.0.0.1:9501\r\nUser-Agent: curl/7.58.0\r\nAccept: */*\r\n\r\n", 425952) = 94mmap(NULL, 2101248, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f61bd028000socket(AF_INET6, SOCK_DGRAM, IPPROTO_IP) = 7close(7) = 0socket(AF_INET, SOCK_STREAM, IPPROTO_IP) = 7fcntl(7, F_GETFL) = 0x2 (flags O_RDWR)fcntl(7, F_SETFL, O_RDWR|O_NONBLOCK) = 0connect(7, { sa_family=AF_INET, sin_port=htons(6379), sin_addr=inet_addr("127.0.0.1")}, 16) = -1 EINPROGRESS (Operation now in progress)poll([{ fd=7, events=POLLIN|POLLOUT|POLLERR|POLLHUP}], 1, 60000) = 1 ([{ fd=7, revents=POLLOUT}])getsockopt(7, SOL_SOCKET, SO_ERROR, [0], [4]) = 0fcntl(7, F_SETFL, O_RDWR) = 0setsockopt(7, SOL_TCP, TCP_NODELAY, [1], 4) = 0setsockopt(7, SOL_SOCKET, SO_KEEPALIVE, [0], 4) = 0poll([{ fd=7, events=POLLIN|POLLPRI|POLLERR|POLLHUP}], 1, 0) = 0 (Timeout)sendto(7, "*2\r\n$3\r\nGET\r\n$3\r\nkey\r\n", 22, MSG_DONTWAIT, NULL, 0) = 22poll([{ fd=7, events=POLLIN|POLLPRI|POLLERR|POLLHUP}], 1, 0) = 1 ([{ fd=7, revents=POLLIN}])recvfrom(7, "$", 1, MSG_PEEK, NULL, NULL) = 1poll([{ fd=7, events=POLLIN|POLLERR|POLLHUP}], 1, 60000) = 1 ([{ fd=7, revents=POLLIN}])recvfrom(7, "$6\r\nvalue2\r\n", 8192, MSG_DONTWAIT, NULL, NULL) = 12getpid() = 1001getpid() = 1001fcntl(4, F_GETFL) = 0x802 (flags O_RDWR|O_NONBLOCK)fcntl(4, F_SETFL, O_RDWR|O_NONBLOCK) = 0sendto(4, "\1\0\0\0\305\0\0\0\0\0\0\0\0\0\0\0HTTP/1.1 200 OK\r\nServer: swoole-http-server\r\nConnection: keep-alive\r\nContent-Type: text/html\r\nDate: Tue, 22 Oct 2019 13:17:45 GMT\r\nContent-Length: 44\r\n\r\nHello Swoole redis val value2 #6094", 213, 0, NULL, 0) = 213munmap(0x7f61bd028000, 2101248) = 0epoll_wait(3, [{ EPOLLIN, { u32=4, u64=12884901892}}], 4096, -1) = 1read(4, "\1\0\0\0\0\0\0\0\0\0\4\0\3\0\0\0", 425952) = 16sendto(4, "\1\0\0\0\0\0\0\0\0\0\4\0\0\0\0\0", 16, 0, NULL, 0) = 16epoll_wait(3, [{ EPOLLIN, { u32=4, u64=12884901892}}], 4096, -1) = 1read(4, "\2\0\0\0N\0\0\0\0\0\0\0\3\0\0\0GET / HTTP/1.1\r\nHost: 127.0.0.1:9501\r\nUser-Agent: curl/7.58.0\r\nAccept: */*\r\n\r\n", 425952) = 94brk(0x556c8977b000) = 0x556c8977b000poll([{ fd=7, events=POLLIN|POLLPRI|POLLERR|POLLHUP}], 1, 0) = 0 (Timeout)sendto(7, "*2\r\n$3\r\nGET\r\n$3\r\nkey\r\n", 22, MSG_DONTWAIT, NULL, 0) = 22poll([{ fd=7, events=POLLIN|POLLPRI|POLLERR|POLLHUP}], 1, 0) = 0 (Timeout)poll([{ fd=7, events=POLLIN|POLLERR|POLLHUP}], 1, 60000) = 1 ([{ fd=7, revents=POLLIN}])recvfrom(7, "$6\r\nvalue2\r\n", 8192, MSG_DONTWAIT, NULL, NULL) = 12sendto(4, "\2\0\0\0\305\0\0\0\0\0\0\0\0\0\0\0HTTP/1.1 200 OK\r\nServer: swoole-http-server\r\nConnection: keep-alive\r\nContent-Type: text/html\r\nDate: Tue, 22 Oct 2019 13:17:46 GMT\r\nContent-Length: 44\r\n\r\n
Hello Swoole redis val value2 #6308", 213, 0, NULL, 0) = 213epoll_wait(3, [{ EPOLLIN, { u32=4, u64=12884901892}}], 4096, -1) = 1read(4, "\2\0\0\0\0\0\0\0\0\0\4\0\3\0\0\0", 425952) = 16sendto(4, "\2\0\0\0\0\0\0\0\0\0\4\0\0\0\0\0", 16, 0, NULL, 0) = 16epoll_wait(3,
可以验证在38行，第二次请求的时候，并没有重新创建连接，完全符合我们程序预期
Step 4
重点来了，通过观察系统调用我们可以发现，以上的例子我们使用的是单进程同步模式，也就是不支持单进程的并发处理．到这里协程的威力要出来了，我们可以支持单进程并发（php对多线程的支持不好，几乎没人使用php的ZTS版本） 重点又又来了，我们需要做的只需要在(new MyServer())->start();前增加一行代码 Swoole\Runtime::enableCoroutine();(new MyServer())->start();
接下来观察工作进程两次请求的系统调用
$ sudo strace -s 1000 -p 1747strace: Process 1747 attachedbrk(0x55f6d8c9e000) = 0x55f6d8c9e000epoll_wait(3, [{ EPOLLIN, { u32=4, u64=12884901892}}], 4096, -1) = 1read(4, "\1\0\0\0N\0\0\0\0\0\0\0\3\0\0\0GET / HTTP/1.1\r\nHost: 127.0.0.1:9501\r\nUser-Agent: curl/7.58.0\r\nAccept: */*\r\n\r\n", 425952) = 94mmap(NULL, 2101248, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f3edce28000socket(AF_INET, SOCK_STREAM|SOCK_CLOEXEC, IPPROTO_IP) = 7fcntl(7, F_GETFL) = 0x2 (flags O_RDWR)fcntl(7, F_SETFL, O_RDWR|O_NONBLOCK) = 0setsockopt(7, SOL_TCP, TCP_NODELAY, [1], 4) = 0setsockopt(7, SOL_TCP, TCP_NODELAY, [1], 4) = 0connect(7, { sa_family=AF_INET, sin_port=htons(6379), sin_addr=inet_addr("127.0.0.1")}, 16) = -1 EINPROGRESS (Operation now in progress)brk(0x55f6d8cc0000) = 0x55f6d8cc0000epoll_ctl(3, EPOLL_CTL_ADD, 7, { EPOLLOUT, { u32=7, u64=25769803783}}) = 0brk(0x55f6d8ca0000) = 0x55f6d8ca0000epoll_wait(3, [{ EPOLLOUT, { u32=7, u64=25769803783}}], 4096, 60000) = 1epoll_ctl(3, EPOLL_CTL_DEL, 7, NULL) = 0getsockopt(7, SOL_SOCKET, SO_ERROR, [0], [4]) = 0setsockopt(7, SOL_TCP, TCP_NODELAY, [1], 4) = 0setsockopt(7, SOL_SOCKET, SO_KEEPALIVE, [0], 4) = 0recvfrom(7, 0x7f3ee07b69ef, 1, MSG_PEEK, NULL, NULL) = -1 EAGAIN (Resource temporarily unavailable)sendto(7, "*2\r\n$3\r\nGET\r\n$3\r\nkey\r\n", 22, 0, NULL, 0) = 22recvfrom(7, 0x7f3ee07b69ef, 1, MSG_PEEK, NULL, NULL) = -1 EAGAIN (Resource temporarily unavailable)recvfrom(7, "$6\r\nvalue2\r\n", 8192, 0, NULL, NULL) = 12getpid() = 1747getpid() = 1747fcntl(4, F_GETFL) = 0x802 (flags O_RDWR|O_NONBLOCK)fcntl(4, F_SETFL, O_RDWR|O_NONBLOCK) = 0sendto(4, "\1\0\0\0\305\0\0\0\0\0\0\0\0\0\0\0HTTP/1.1 200 OK\r\nServer: swoole-http-server\r\nConnection: keep-alive\r\nContent-Type: text/html\r\nDate: Tue, 22 Oct 2019 13:27:04 GMT\r\nContent-Length: 44\r\n\r\nHello Swoole redis val value2 #3338", 213, 0, NULL, 0) = 213munmap(0x7f3edce28000, 2101248) = 0epoll_wait(3, [{ EPOLLIN, { u32=4, u64=12884901892}}], 4096, -1) = 1read(4, "\1\0\0\0\0\0\0\0\0\0\4\0\3\0\0\0", 425952) = 16sendto(4, "\1\0\0\0\0\0\0\0\0\0\4\0\0\0\0\0", 16, 0, NULL, 0) = 16epoll_wait(3, [{ EPOLLIN, { u32=4, u64=12884901892}}], 4096, -1) = 1read(4, "\2\0\0\0N\0\0\0\0\0\0\0\3\0\0\0GET / HTTP/1.1\r\nHost: 127.0.0.1:9501\r\nUser-Agent: curl/7.58.0\r\nAccept: */*\r\n\r\n", 425952) = 94brk(0x55f6d8ec0000) = 0x55f6d8ec0000recvfrom(7, 0x7f3ee07b69ef, 1, MSG_PEEK, NULL, NULL) = -1 EAGAIN (Resource temporarily unavailable)sendto(7, "*2\r\n$3\r\nGET\r\n$3\r\nkey\r\n", 22, 0, NULL, 0) = 22recvfrom(7, "$", 1, MSG_PEEK, NULL, NULL) = 1recvfrom(7, "$6\r\nvalue2\r\n", 8192, 0, NULL, NULL) = 12sendto(4, "\2\0\0\0\305\0\0\0\0\0\0\0\0\0\0\0HTTP/1.1 200 OK\r\nServer: swoole-http-server\r\nConnection: keep-alive\r\nContent-Type: text/html\r\nDate: Tue, 22 Oct 2019 13:28:50 GMT\r\nContent-Length: 44\r\n\r\n
Hello Swoole redis val value2 #1576", 213, 0, NULL, 0) = 213brk(0x55f6d8ca0000) = 0x55f6d8ca0000epoll_wait(3, [{ EPOLLIN, { u32=4, u64=12884901892}}], 4096, -1) = 1read(4, "\2\0\0\0\0\0\0\0\0\0\4\0\3\0\0\0", 425952) = 16sendto(4, "\2\0\0\0\0\0\0\0\0\0\4\0\0\0\0\0", 16, 0, NULL, 0) = 16epoll_wait(3,
可以发现是通过epoll_wait来监听redis句柄的读写事件．
但是有个问题，如果当前时间有大量的请求涌入，会建立大量的redis连接，对后端服务造成杀伤，我们来通过ab压测演示一下$ ab -c 1000 -n 10000 'http://127.0.0.1:9501/'This is ApacheBench, Version 2.3 <$Revision: 1807734 $>Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/Licensed to The Apache Software Foundation, http://www.apache.org/Benchmarking 127.0.0.1 (be patient)Completed 1000 requestsCompleted 2000 requestsCompleted 3000 requestsCompleted 4000 requestsCompleted 5000 requestsCompleted 6000 requestsCompleted 7000 requestsCompleted 8000 requestsCompleted 9000 requestsCompleted 10000 requestsFinished 10000 requestsServer Software: swoole-http-serverServer Hostname: 127.0.0.1Server Port: 9501Document Path: /Document Length: 44 bytesConcurrency Level: 1000Time taken for tests: 0.512 secondsComplete requests: 10000Failed requests: 0Total transferred: 1920000 bytesHTML transferred: 440000 bytesRequests per second: 19528.96 [#/sec] (mean)Time per request: 51.206 [ms] (mean)Time per request: 0.051 [ms] (mean, across all concurrent requests)Transfer rate: 3661.68 [Kbytes/sec] receivedConnection Times (ms) min mean[+/-sd] median maxConnect: 0 3 5.8 2 39Processing: 1 5 6.3 4 61Waiting: 1 4 6.3 3 61Total: 4 7 9.2 5 64Percentage of the requests served within a certain time (ms) 50% 5 66% 6 75% 6 80% 6 90% 7 95% 38 98% 44 99% 56 100% 64 (longest request)
然后通过查看通过压测建立了多少连接
$ lsof -p 2323 | grep 'localhost:6379 (ESTABLISHED)' | wc -l 129
这里只是本地使用redis执行最简单的操作，如果请求IO时间较长，连接不能及时释放，会建立更多的连接．这里会对后端造成不可预估的杀伤．有没有什么办法可以限制并发数，对服务资源进行控制呢，答案是肯定的．我们可以使用channel来限制并发
Step 5
server = $server; $this->pool = new \SplQueue(); } function request($request, $response){ $this->chan->push(true); if ($this->pool->count() > 0) { $redis = $this->pool->pop(); } else { $redis = new redis; $redis->connect("127.0.0.1", 6379); } $val = $redis->get("key"); $response->end("Hello Swoole redis val $val #" . rand(1000, 9999) . ""); $this->pool->push($redis); $this->chan->pop(); } function workerStart($server, $worker_id){ echo "worker start $worker_id\n"; Swoole\Runtime::enableCoroutine(); $this->chan = new Swoole\Coroutine\Channel(10); } function start(){ $this->server->on('request', [$this, "request"]); $this->server->on('workerStart', [$this, "workerStart"]); $this->server->set([ 'worker_num' => 1 ]); $this->server->start(); }}(new MyServer())->start();
我们对上面的代码进行多次压测，
$ ab -c 1000 -n 10000 'http://127.0.0.1:9501/'This is ApacheBench, Version 2.3 <$Revision: 1807734 $>Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/Licensed to The Apache Software Foundation, http://www.apache.org/Benchmarking 127.0.0.1 (be patient)Completed 1000 requestsCompleted 2000 requestsCompleted 3000 requestsCompleted 4000 requestsCompleted 5000 requestsCompleted 6000 requestsCompleted 7000 requestsCompleted 8000 requestsCompleted 9000 requestsCompleted 10000 requestsFinished 10000 requestsServer Software: swoole-http-serverServer Hostname: 127.0.0.1Server Port: 9501Document Path: /Document Length: 44 bytesConcurrency Level: 1000Time taken for tests: 0.477 secondsComplete requests: 10000Failed requests: 0Total transferred: 1920000 bytesHTML transferred: 440000 bytesRequests per second: 20949.87 [#/sec] (mean)Time per request: 47.733 [ms] (mean)Time per request: 0.048 [ms] (mean, across all concurrent requests)Transfer rate: 3928.10 [Kbytes/sec] receivedConnection Times (ms) min mean[+/-sd] median maxConnect: 4 17 4.0 18 24Processing: 8 28 5.5 29 43Waiting: 5 23 6.0 23 39Total: 27 46 3.9 46 56Percentage of the requests served within a certain time (ms) 50% 46 66% 47 75% 48 80% 49 90% 50 95% 52 98% 53 99% 53 100% 56 (longest request)
发现最多只会有10个连接，这里的连接数是我们进行硬编码设置．
$ lsof -p 5093 | grep 'localhost:6379 (ESTABLISHED)' | wc -l 10
总结
需要说明的是，我们的实例代码只是演示，很多地方并不严谨而且没有模块化的封装，例如redis连接的建立没有检查成功，也没有处理redis请求的失败重连，还有很多细节需要完善．在生产环境当中，需要对外部的每一项资源保持警惕，不信任．连接很可能被服务端切断．这里也没有涉及到用户提交的参数等过程． 我们通过渐进式的演进，来验证长连接的作用和使用方式，并且学会通过channel掌控并发能力，保护当前服务的资源，包括后端的资源，使我们的服务稳定，健壮．转载地址：http://ogxui.baihongyu.com/