連接失效問題
#範例
##其中，Redis常見的報錯就是：設定項：timeout
Error while reading line from the server
MySQL常見的錯誤：##設定項目：
wait_timeout & interactive_timeout報錯訊息：
和Redis伺服器一樣，MySQL也會定時的去清理掉沒用的連線。
1、用的時候進行重連
2、定時發送心跳維持連結
用的時候進行重連
優點是簡單，缺點是面臨短連線的問題。
定時發送心跳維持連結
推薦。
如何維持長連線
tcp協定中實現的
tcp_keepalive
作業系統底層提供了一組tcp的
keepalive設定：<div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">tcp_keepalive_time (integer; default: 7200; since Linux 2.2)
The number of seconds a connection needs to be idle before TCP
begins sending out keep-alive probes. Keep-alives are sent only
when the SO_KEEPALIVE socket option is enabled. The default
value is 7200 seconds (2 hours). An idle connection is
terminated after approximately an additional 11 minutes (9
probes an interval of 75 seconds apart) when keep-alive is
enabled.
Note that underlying connection tracking mechanisms and
application timeouts may be much shorter.
tcp_keepalive_intvl (integer; default: 75; since Linux 2.4)
The number of seconds between TCP keep-alive probes.
tcp_keepalive_probes (integer; default: 9; since Linux 2.2)
The maximum number of TCP keep-alive probes to send before
giving up and killing the connection if no response is obtained
from the other end.
8</pre><div class="contentsignin">登入後複製</div></div>Swoole底層把這些設定開放出來了，例如：
?php $server = new \Swoole\Server('127.0.0.1', 6666, SWOOLE_PROCESS); $server->set([ 'worker_num' => 1, 'open_tcp_keepalive' => 1, 'tcp_keepidle' => 4, // 对应tcp_keepalive_time 'tcp_keepinterval' => 1, // 对应tcp_keepalive_intvl 'tcp_keepcount' => 5, // 对应tcp_keepalive_probes ]);
其中：
'open_tcp_keepalive' => 1, // 总开关，用来开启tcp_keepalive 'tcp_keepidle' => 4, // 4s没有数据传输就进行检测 // 检测的策略如下： 'tcp_keepinterval' => 1, // 1s探测一次，即每隔1s给客户端发一个包（然后客户端可能会回一个ack的包，如果服务端收到了这个ack包，那么说明这个连接是活着的） 'tcp_keepcount' => 5, // 探测的次数，超过5次后客户端还没有回ack包，那么close此连接
我們來實戰測試體驗一下，服務端腳本如下：
<?php
$server = new \Swoole\Server('127.0.0.1', 6666, SWOOLE_PROCESS);
$server->set([
'worker_num' => 1,
'open_tcp_keepalive' => 1, // 开启tcp_keepalive
'tcp_keepidle' => 4, // 4s没有数据传输就进行检测
'tcp_keepinterval' => 1, // 1s探测一次
'tcp_keepcount' => 5, // 探测的次数，超过5次后还没有回包close此连接
]);
$server->on('connect', function ($server, $fd) {
var_dump("Client: Connect $fd");
});
$server->on('receive', function ($server, $fd, $reactor_id, $data) {
var_dump($data);
});
$server->on('close', function ($server, $fd) {
var_dump("close fd $fd");
});
$server->start();我們啟動這個伺服器：
~/codeDir/phpCode/hyperf-skeleton # php server.php
然後透過tcpdump來抓包：
##~/codeDir/phpCode /hyperf-skeleton # tcpdump -i lo port 6666
tcpdump: verbose output suppressed, use -v or -vv for full protocol decodelistening on lo, link-type EN10MB (Ethercodelistening on lo, link-type EN10MB (Ether0) , capture size 262144 bytes我們此時正在監聽lo上的6666埠的資料包。 然後我們用客戶端去連接它：
~/codeDir/phpCode/hyperf-skeleton # nc 127.0.0.1 6666
~/codeDir/phpCode/hyperf-skeleton # php server.php string(17) "Client: Connect 1"
01:48:40.178439 IP localhost.33933 > localhost.6666: Flags [S], seq 43162537, win 43690, options [mss 65495,sackOK,TS val 9833698 ecr 0,nop,wscale 7], length 0 01:48:40.178484 IP localhost.6666 > localhost.33933: Flags [S.], seq 1327460565, ack 43162538, win 43690, options [mss 65495,sackOK,TS val 9833698 ecr 9833698,nop,wscale 7], length 0 01:48:40.178519 IP localhost.33933 > localhost.6666: Flags [.], ack 1, win 342, options [nop,nop,TS val 9833698 ecr 9833698], length 0 01:48:44.229926 IP localhost.6666 > localhost.33933: Flags [.], ack 1, win 342, options [nop,nop,TS val 9834104 ecr 9833698], length 0 01:48:44.229951 IP localhost.33933 > localhost.6666: Flags [.], ack 1, win 342, options [nop,nop,TS val 9834104 ecr 9833698], length 0 01:48:44.229926 IP localhost.6666 > localhost.33933: Flags [.], ack 1, win 342, options [nop,nop,TS val 9834104 ecr 9833698], length 0 01:48:44.229951 IP localhost.33933 > localhost.6666: Flags [.], ack 1, win 342, options [nop,nop,TS val 9834104 ecr 9833698], length 0 01:48:44.229926 IP localhost.6666 > localhost.33933: Flags [.], ack 1, win 342, options [nop,nop,TS val 9834104 ecr 9833698], length 0 // 省略了其他的输出
01:48:40.178439 IP localhost.33933 > localhost.6666: Flags [S], seq 43162537, win 43690, options [mss 65495,sackOK,TS val 9833698 ecr 0,nop,wscale 7], length 0 01:48:40.178484 IP localhost.6666 > localhost.33933: Flags [S.], seq 1327460565, ack 43162538, win 43690, options [mss 65495,sackOK,TS val 9833698 ecr 9833698,nop,wscale 7], length 0 01:48:40.178519 IP localhost.33933 > localhost.6666: Flags [.], ack 1, win 342, options [nop,nop,TS val 9833698 ecr 9833698], length 0
01:52:54.359341 IP localhost.6666 > localhost.43101: Flags [.], ack 1, win 342, options [nop,nop,TS val 9859144 ecr 9858736], length 0 01:52:54.359377 IP localhost.43101 > localhost.6666: Flags [.], ack 1, win 342, options [nop,nop,TS val 9859144 ecr 9855887], length 0
'tcp_keepinterval' => 1, // 1s探测一次 'tcp_keepcount' => 5, // 探测的次数，超过5次后还没有回包close此连接
01:52:54.359341 IP localhost.6666 > localhost.43101: Flags [.], ack 1, win 342, options [nop,nop,TS val 9859144 ecr 9858736], length 0 01:52:54.359377 IP localhost.43101 > localhost.6666: Flags [.], ack 1, win 342, options [nop,nop,TS val 9859144 ecr 9855887], length 0
~/codeDir/phpCode/hyperf-skeleton # iptables -A INPUT -p tcp --dport 6666 -j DROP
~/codeDir/phpCode/hyperf-skeleton # php server.php string(17) "Client: Connect 1" string(10) "close fd 1"
~/codeDir/phpCode # iptables -D INPUT -p tcp -m tcp --dport 6666 -j DROP
'heartbeat_check_interval' => 1, // 1s探测一次 'heartbeat_idle_time' => 5, // 5s未发送数据包就close此连接
<?php
$server = new \Swoole\Server('127.0.0.1', 6666, SWOOLE_PROCESS);
$server->set([
'worker_num' => 1,
'heartbeat_check_interval' => 1, // 1s探测一次
'heartbeat_idle_time' => 5, // 5s未发送数据包就close此连接
]);
$server->on('connect', function ($server, $fd) {
var_dump("Client: Connect $fd");
});
$server->on('receive', function ($server, $fd, $reactor_id, $data) {
var_dump($data);
});
$server->on('close', function ($server, $fd) {
var_dump("close fd $fd");
});
$server->start();~/codeDir/phpCode/hyperf- skeleton # php server.php然後啟動tcpdump：
~/codeDir/phpCode # tcpdump -i lo port 6666 tcpdump: verbose output suppressed, use -v or -vv for full protocol decode listening on lo, link-type EN10MB (Ethernet), capture size 262144 bytes
~/codeDir/phpCode/hyperf-skeleton # nc 127.0.0.1 6666此時服務器端打印：
~/codeDir/phpCode/hyperf-skeleton # php server.php string(17) "Client: Connect 1"
02:48:32.516093 IP localhost.42123 > localhost.6666: Flags [S], seq 1088388248, win 43690, options [mss 65495,sackOK,TS val 10193342 ecr 0,nop,wscale 7], length 0 02:48:32.516133 IP localhost.6666 > localhost.42123: Flags [S.], seq 80508236, ack 1088388249, win 43690, options [mss 65495,sackOK,TS val 10193342 ecr 10193342,nop,wscale 7], length 0 02:48:32.516156 IP localhost.42123 > localhost.6666: Flags [.], ack 1, win 342, options [nop,nop,TS val 10193342 ecr 10193342], length 0
# 02:48:36.992172 IP localhost.42123 > 6 6,6068:628: 6628:628:628: 6628:6868:628:628: 6628:6628:628: 6628:626980000000 win 342, options [nop,nop,TS val 10193790 ecr 10193789], length 0
也就是服務端發送了FIN包。因為客戶端沒有發送數據，所以Swoole關閉了連線。
然後伺服器端會列印：
~/codeDir/phpCode/hyperf-skeleton # php server.php string(17) "Client: Connect 1" string(10) "close fd 1"
所以，heartbeat和tcp keepalive還是有一定的差別的，tcp keepalive有保活連結的功能，但是heartbeat存粹是偵測沒有資料的連接，然後關閉它，並且只可以在服務端這邊配置，如果需要保活，也可以讓客戶端配合發送心跳。
如果我们不想让服务端close掉连接，那么就得在应用层里面不断的发送数据包来进行保活，例如我在nc客户端里面不断的发送包：
~/codeDir/phpCode/hyperf-skeleton # nc 127.0.0.1 6666 ping ping ping ping ping ping ping ping ping
我发送了9个ping包给服务器，tcpdump的输出如下：
// 省略了三次握手的包 02:57:53.697363 IP localhost.44195 > localhost.6666: Flags [P.], seq 1:6, ack 1, win 342, options [nop,nop,TS val 10249525 ecr 10249307], length 5 02:57:53.697390 IP localhost.6666 > localhost.44195: Flags [.], ack 6, win 342, options [nop,nop,TS val 10249525 ecr 10249525], length 0 02:57:55.309532 IP localhost.44195 > localhost.6666: Flags [P.], seq 6:11, ack 1, win 342, options [nop,nop,TS val 10249686 ecr 10249525], length 5 02:57:55.309576 IP localhost.6666 > localhost.44195: Flags [.], ack 11, win 342, options [nop,nop,TS val 10249686 ecr 10249686], length 0 02:57:58.395206 IP localhost.44195 > localhost.6666: Flags [P.], seq 11:16, ack 1, win 342, options [nop,nop,TS val 10249994 ecr 10249686], length 5 02:57:58.395239 IP localhost.6666 > localhost.44195: Flags [.], ack 16, win 342, options [nop,nop,TS val 10249994 ecr 10249994], length 0 02:58:01.858094 IP localhost.44195 > localhost.6666: Flags [P.], seq 16:21, ack 1, win 342, options [nop,nop,TS val 10250341 ecr 10249994], length 5 02:58:01.858126 IP localhost.6666 > localhost.44195: Flags [.], ack 21, win 342, options [nop,nop,TS val 10250341 ecr 10250341], length 0 02:58:04.132584 IP localhost.44195 > localhost.6666: Flags [P.], seq 21:26, ack 1, win 342, options [nop,nop,TS val 10250568 ecr 10250341], length 5 02:58:04.132609 IP localhost.6666 > localhost.44195: Flags [.], ack 26, win 342, options [nop,nop,TS val 10250568 ecr 10250568], length 0 02:58:05.895704 IP localhost.44195 > localhost.6666: Flags [P.], seq 26:31, ack 1, win 342, options [nop,nop,TS val 10250744 ecr 10250568], length 5 02:58:05.895728 IP localhost.6666 > localhost.44195: Flags [.], ack 31, win 342, options [nop,nop,TS val 10250744 ecr 10250744], length 0 02:58:07.150265 IP localhost.44195 > localhost.6666: Flags [P.], seq 31:36, ack 1, win 342, options [nop,nop,TS val 10250870 ecr 10250744], length 5 02:58:07.150288 IP localhost.6666 > localhost.44195: Flags [.], ack 36, win 342, options [nop,nop,TS val 10250870 ecr 10250870], length 0 02:58:08.349124 IP localhost.44195 > localhost.6666: Flags [P.], seq 36:41, ack 1, win 342, options [nop,nop,TS val 10250990 ecr 10250870], length 5 02:58:08.349156 IP localhost.6666 > localhost.44195: Flags [.], ack 41, win 342, options [nop,nop,TS val 10250990 ecr 10250990], length 0 02:58:09.906223 IP localhost.44195 > localhost.6666: Flags [P.], seq 41:46, ack 1, win 342, options [nop,nop,TS val 10251145 ecr 10250990], length 5 02:58:09.906247 IP localhost.6666 > localhost.44195: Flags [.], ack 46, win 342, options [nop,nop,TS val 10251145 ecr 10251145], length 0
有9组数据包的发送。（这里的Flags [P.]代表Push的含义）
此时服务器还没有close掉连接，实现了客户端保活连接的功能。然后我们停止发送ping，过了5秒后tcpdump就会输出一组：
02:58:14.811761 IP localhost.6666 > localhost.44195: Flags [F.], seq 1, ack 46, win 342, options [nop,nop,TS val 10251636 ecr 10251145], length 0
02:58:14.816420 IP localhost.44195 > localhost.6666: Flags [.], ack 2, win 342, options [nop,nop,TS val 10251637 ecr 10251636], length 0
服务端那边发送了FIN包，说明服务端close掉了连接。服务端的输出如下：
~/codeDir/phpCode/hyperf-skeleton # php server.php string(17) "Client: Connect 1" string(5) "ping " string(5) "ping " string(5) "ping " string(5) "ping " string(5) "ping " string(5) "ping " string(5) "ping " string(5) "ping " string(5) "ping " string(10) "close fd 1"
然后我们在客户端那边ctrl + c来关闭连接：
~/codeDir/phpCode/hyperf-skeleton # nc 127.0.0.1 6666 ping ping ping ping ping ping ping ping ping ^Cpunt! ~/codeDir/phpCode/hyperf-skeleton #
此时，tcpdump的输出如下：
03:03:02.257667 IP localhost.44195 > localhost.6666: Flags [F.], seq 46, ack 2, win 342, options [nop,nop,TS val 10280414 ecr 10251636], length 0 03:03:02.257734 IP localhost.6666 > localhost.44195: Flags [R], seq 2678621620, win 0, length 0
应用层心跳
1、制定ping/pong协议（mysql等自带ping协议）
2、客户端灵活的发送ping心跳包
3、服务端OnRecive检查可用性回复pong
例如：
$server->on('receive', function (\Swoole\Server $server, $fd, $reactor_id, $data)
{
if ($data == 'ping')
{
checkDB();
checkServiceA();
checkRedis();
$server->send('pong');
}
});
结论
1、tcp的keepalive最简单，但是有兼容性问题，不够灵活
2、swoole提供的keepalive最实用，但是需要客户端配合，复杂度适中
3、应用层的keepalive最灵活但是最麻烦
以上是PHP Swoole長連結常見問題總結的詳細內容。更多資訊請關注PHP中文網其他相關文章！
