爲何每次app訪問服務器都創建新鏈接 致使服務器大量鏈接瘋漲

運維發現服務器有大量鏈接不釋放，並且每次app訪問都會創建新鏈接。

netstat -antlp |grep ESTAB|grep 8080|wc -l    （訪問服務器8080端口的已創建的鏈接數）

後來用瀏覽器測試沒問題。接着發現終端鏈接時，設置了http header: Connection: keep-alive 。可是一樣用postman模擬，也沒問題。最終發現應該是app寫了keepalive，鏈接調用時確沒有用之前打開的鏈接，而是新建一個鏈接。

而服務器端wildfly默認打開了keepalive，並且永遠不會超時。wildfy的undertow添加keepalive超時設置以下：ms

 <http-listener name="default" max-post-size="204857600" socket-binding="http" redirect-socket="https" tcp-keep-alive="true" read-timeout="30000"/>

 

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用telnet模擬http 客戶端調用，能夠看到當服務器返回內容後，鏈接並無斷開，直到超時。

以下示例在一個打開的鏈接裏面，作了兩次post。

>telnet 211.100.75.241 8080
Trying 211.100.75.241...
Connected to 211.100.75.241.
Escape character is '^]'.
POST /Message/update HTTP/1.1
Host: 211.100.75.241:8080
Connection: keep-alive
Content-Length: 31
Cache-Control: max-age=0
Upgrade-Insecure-Requests: 1
Origin: null
Content-Type: application/x-www-form-urlencoded
User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.26 Safari/537.36 Core/1.63.5702.400 QQBrowser/10.2.1893.400
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8
DNT: 1
Accept-Encoding: gzip, deflate
Accept-Language: zh-CN,zh;q=0.9

mac=00%3A07%3A63%3Ae2%3Aa7%3A62
HTTP/1.1 200 OK
Connection: keep-alive
X-Powered-By: Undertow/1
Server: WildFly/10
Content-Type: application/json;charset=UTF-8
Content-Length: 1
Date: Mon, 06 Aug 2018 08:48:58 GMT


POST /Message/update HTTP/1.1
Host: 211.100.75.241:8080
Connection: keep-alive
Content-Length: 31
Cache-Control: max-age=0
Upgrade-Insecure-Requests: 1
Origin: null
Content-Type: application/x-www-form-urlencoded
User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.26 Safari/537.36 Core/1.63.5702.400 QQBrowser/10.2.1893.400
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8
DNT: 1
Accept-Encoding: gzip, deflate
Accept-Language: zh-CN,zh;q=0.9

mac=00%3A07%3A63%3Ae2%3Aa7%3A62
HTTP/1.1 200 OK
Connection: keep-alive
X-Powered-By: Undertow/1
Server: WildFly/10
Content-Type: application/json;charset=UTF-8
Content-Length: 1
Date: Mon, 06 Aug 2018 08:49:05 GMT


Connection closed by foreign host.