网络端口占用问题的综合调研与解决方案

// Netty框架Caused by: java.net.BindException: Address already in use
// JettyFailed to start jetty server at port 8080, cause: Address already in use
// Embedded TomcatEmbedded servlet container failed to start. Port 8080 was already in use.
// TomcatThe Tomcat connector configured to listen on port 8080 failed to start. The port ay already be in use or the connector may be misconfigured.

//  系统调用bind()对应的入口函数是__sys_bind()//  端口被占用判断逻辑是inet_bind_conflict函数
static bool inet_bind_conflict(const struct sock *sk, struct sock *sk2,			       kuid_t sk_uid, bool relax,			       bool reuseport_cb_ok, bool reuseport_ok){	int bound_dev_if2;
	if (sk == sk2)		return false;
	bound_dev_if2 = READ_ONCE(sk2->sk_bound_dev_if);
	if (!sk->sk_bound_dev_if || !bound_dev_if2 ||	    sk->sk_bound_dev_if == bound_dev_if2) {		if (sk->sk_reuse && sk2->sk_reuse &&		    sk2->sk_state != TCP_LISTEN) {			if (!relax || (!reuseport_ok && sk->sk_reuseport &&				       sk2->sk_reuseport && reuseport_cb_ok &&				       (sk2->sk_state == TCP_TIME_WAIT ||					uid_eq(sk_uid, sock_i_uid(sk2)))))				return true;		} else if (!reuseport_ok || !sk->sk_reuseport ||			   !sk2->sk_reuseport || !reuseport_cb_ok ||			   (sk2->sk_state != TCP_TIME_WAIT &&			    !uid_eq(sk_uid, sock_i_uid(sk2)))) {			return true;		}	}	return false;}

// 端口被占用判断字段sk_bound_dev_if --> 网卡编号sk_reuse --> 套接字复用sk_reuseport --> 端口复用sk_state --> 当前状态listen还是time_waitsk_uid socket --> 所属用户IDreuseport_cb_ok --> 内核是否支持端口复用

# 增加一个busybox的init容器，修改完端口复用开关后退出
apiVersion: apps/v1kind: Deploymentmetadata:  name: my-deploymentspec:  replicas: 2  selector:    matchLabels:      app: my-app  template:    metadata:      labels:        app: my-app    spec:      containers:      - name: my-container        image: nginx      initContainers:      - name: sysctl-modifier        image: busybox        securityContext:          privileged: true        command: ["sysctl -w net.ipv4.tcp_tw_reuse=1 && exit"]