问题排查：haproxy tcp 长连接没有 failover

            The tunnel timeout applies when a bidirectional connection is established
            between a client and a server, and the connection remains inactive in both
            directions. This timeout supersedes both the client and server timeouts once
            the connection becomes a tunnel. In TCP, this timeout is used as soon as no
            analyser remains attached to either connection (eg: tcp content rules are
            accepted). In HTTP, this timeout is used when a connection is upgraded (eg:
            when switching to the WebSocket protocol, or forwarding a CONNECT request
            to a proxy), or after the first response when no keepalive/close option is
            specified.

            Since this timeout is usually used in conjunction with long-lived connections,
            it usually is a good idea to also set “timeout client-fin” to handle the
            situation where a client suddenly disappears from the net and does not
            acknowledge a close, or sends a shutdown and does not acknowledge pending
            data anymore. This can happen in lossy networks where firewalls are present,
            and is detected by the presence of large amounts of sessions in a FIN_WAIT
            state.
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