Java outgoing TCP connection failover based on multiple DNS results
If I make a connection using new Socket("unit.domain.com", 100)
and the unit.domain.com
DNS record has multiple IP addresses in the A record.. In the event of a failed connection, Does Java automati开发者_运维技巧cally connect to one of the other addresses in the list like the browser does? or does that have to be implemented manually?
No! Creating a socket via new Socket(String, int) results in a resolving like that
addr = InetAddress.getByName(hostname);
which is a shortcut for
return InetAddress.getAllByName(host)[0];
The address resolution is performed in the Socket c-tor.
If you have to reconnect (failover) use the result returned by InetAddress.getAllByName(host), randomize (or use round-robin) and connect to the necessary addresses.
Edit: also if you are going to need to connect with some likely failure, you'd be better off using connect method of the Socket class with a timeout. Also make sure you close even failed sockets (and esp. channels) since they may leak a FD on *Nix.
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