Re: How to reuse TCP listening socket immediately after it was connected at least once?
In message gvqh4p$ob...@news.lysator.liu.se, Thomas Bellman wrote: We weren't exactly keen on rebooting the machine, but it was the fastest way of getting out of that situation that we could figure out. How *should* we have dealt with it in your opinion? Remember, the timed_wait timeout is there for a reason, and trying to defeat it could reduce the reliability of your application--that's why cutting corners is a bad idea. If you want to minimize the effect of the timeout, then just use different ports, and have the clients find them via DNS SRV records. -- http://mail.python.org/mailman/listinfo/python-list
Re: How to reuse TCP listening socket immediately after it was connected at least once?
Lawrence D'Oliveiro l...@geek-central.gen.new_zealand wrote: In message gvlppt$hk...@news.lysator.liu.se, Thomas Bellman wrote: Speaking as a sysadmin, running applications for production, programs not using SO_REUSEADDR should be taken out and shot. Not using SO_REUSEADDR means forcing a service interruption of half an hour (IIRC) if for some reason the service must be restarted, or having to reboot the entire machine. No, you do not recall correctly. *Tests* It seems to be 100 seconds in Fedora 9 and 60 seconds in Solaris 10. OK, that amount of time is not totally horrible, in many cases just annoying. Still much longer for an interruption of service that could have been just 1-2 seconds. However, I *have* used systems where it took much longer. It was slightly more than ten years ago, under an earlier version of Solaris 2, problably 2.4. It may be that it only took that long under certain circumstances that the application we used always triggered, but we did have to wait several tens of minutes. It was way faster to reboot the machine than waiting for the sockets to time out. And anybody wanting to reboot a machine to work around a problem like that should be taken out and shot. We weren't exactly keen on rebooting the machine, but it was the fastest way of getting out of that situation that we could figure out. How *should* we have dealt with it in your opinion? -- Thomas Bellman, Lysator Computer Club, Linköping University, Sweden God is real, but Jesus is an integer. ! bellman @ lysator.liu.se ! Make Love -- Nicht Wahr! -- http://mail.python.org/mailman/listinfo/python-list
Re: How to reuse TCP listening socket immediately after it was connected at least once?
Roy Smith r...@panix.com wrote: In article gvb8fn$7g...@lust.ihug.co.nz, Lawrence D'Oliveiro l...@geek-central.gen.new_zealand wrote: The right thing to do is try to ensure that all your connections are properly closed at shutdown. That may not be enough (if your server crashes due to bugs), so the other thing you need to do is retry the socket open, say, at 30-second intervals, until it succeeds. That may be a reasonable thing to do for production code, but when you're building and debugging a server, it's a real pain to not be able to restart it quickly whenever you want (or need) to. Speaking as a sysadmin, running applications for production, programs not using SO_REUSEADDR should be taken out and shot. You *can't* ensure that TCP connections are properly closed. For example, a *client* crashing, or otherwise becoming unreachable, will leave TCP connections unclosed, no matter what you do. Not using SO_REUSEADDR means forcing a service interruption of half an hour (IIRC) if for some reason the service must be restarted, or having to reboot the entire machine. No thanks. I have been in that situation. -- Thomas Bellman, Lysator Academic Computer Club, Linköping University Never let your sense of morals prevent you! Sweden ; +46-13 177780 from doing what is right. -- Salvor Hardin ! bell...@lysator.liu.se -- http://mail.python.org/mailman/listinfo/python-list
Re: How to reuse TCP listening socket immediately after it was connected at least once?
In message gvlppt$hk...@news.lysator.liu.se, Thomas Bellman wrote: Speaking as a sysadmin, running applications for production, programs not using SO_REUSEADDR should be taken out and shot. Not using SO_REUSEADDR means forcing a service interruption of half an hour (IIRC) if for some reason the service must be restarted, or having to reboot the entire machine. No, you do not recall correctly. And anybody wanting to reboot a machine to work around a problem like that should be taken out and shot. -- http://mail.python.org/mailman/listinfo/python-list
Re: How to reuse TCP listening socket immediately after it was connected at least once?
In message roy-50fe2e.07273725052...@news.panix.com, Roy Smith wrote: In article gvd1id$8j...@lust.ihug.co.nz, Lawrence D'Oliveiro l...@geek-central.gen.new_zealand wrote: In message roy-3c4ded.09214724052...@news.panix.com, Roy Smith wrote: In article gvb8fn$7g...@lust.ihug.co.nz, Lawrence D'Oliveiro l...@geek-central.gen.new_zealand wrote: The right thing to do is try to ensure that all your connections are properly closed at shutdown. That may not be enough (if your server crashes due to bugs), so the other thing you need to do is retry the socket open, say, at 30-second intervals, until it succeeds. That may be a reasonable thing to do for production code, but when you're building and debugging a server, it's a real pain to not be able to restart it quickly whenever you want (or need) to. On the contrary, I run exactly the same logic--and that includes socket- handling logic--in both test and production servers. How else can I be sure it'll work properly in production? I was just pointing out how it can be useful in cases such as the OP's, where he's getting bind errors when he restarts his server. And I was pointing out how important it was to make sure your code deals gracefully with those errors. -- http://mail.python.org/mailman/listinfo/python-list
Re: How to reuse TCP listening socket immediately after it was connected at least once?
In message mailman.651.1243154739.8015.python-l...@python.org, Igor Katson wrote: I have written a socket server and some arbitrary clients. When I shutdown the server, and do socket.close(), I cannot immediately start it again cause it has some open sockets in TIME_WAIT state. It throws address already in use exception at me. There's a reason for that. It's to ensure that there are no leftover packets floating around the Internet somewhere, that you might mistakenly receive and think they were part of a new connection, when they were in fact part of an old one. The right thing to do is try to ensure that all your connections are properly closed at shutdown. That may not be enough (if your server crashes due to bugs), so the other thing you need to do is retry the socket open, say, at 30-second intervals, until it succeeds. -- http://mail.python.org/mailman/listinfo/python-list
Re: How to reuse TCP listening socket immediately after it was connected at least once?
I have written a socket server and some arbitrary clients. When I shutdown the server, and do socket.close(), I cannot immediately start it again cause it has some open sockets in TIME_WAIT state. It throws address already in use exception at me. I have searched for that in google but haven't found a way to solve that. Tried setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) but that does not help. This should work, AFAIK you only need to do it before you call .bind(..) on the accept-ing socket -- дамјан ( http://softver.org.mk/damjan/ ) Give me the knowledge to change the code I do not accept, the wisdom not to accept the code I cannot change, and the freedom to choose my preference. -- http://mail.python.org/mailman/listinfo/python-list
Re: How to reuse TCP listening socket immediately after it was connected at least once?
In article gvd1id$8j...@lust.ihug.co.nz, Lawrence D'Oliveiro l...@geek-central.gen.new_zealand wrote: In message roy-3c4ded.09214724052...@news.panix.com, Roy Smith wrote: In article gvb8fn$7g...@lust.ihug.co.nz, Lawrence D'Oliveiro l...@geek-central.gen.new_zealand wrote: The right thing to do is try to ensure that all your connections are properly closed at shutdown. That may not be enough (if your server crashes due to bugs), so the other thing you need to do is retry the socket open, say, at 30-second intervals, until it succeeds. That may be a reasonable thing to do for production code, but when you're building and debugging a server, it's a real pain to not be able to restart it quickly whenever you want (or need) to. On the contrary, I run exactly the same logic--and that includes socket- handling logic--in both test and production servers. How else can I be sure it'll work properly in production? If running without SO_REUASEADDR works for you, that's great. I was just pointing out how it can be useful in cases such as the OP's, where he's getting bind errors when he restarts his server. -- http://mail.python.org/mailman/listinfo/python-list
Re: How to reuse TCP listening socket immediately after it was connected at least once?
Igor Katson wrote: I have written a socket server and some arbitrary clients. When I shutdown the server, and do socket.close(), I cannot immediately start it again cause it has some open sockets in TIME_WAIT state. It throws address already in use exception at me. I have searched for that in google but haven't found a way to solve that. Tried setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) but that does not help. Is there a nice way to overcome this? Solved myself. SO_REUSEADDE should be used on the second listening socket creation (while time_wait already hangs) -- http://mail.python.org/mailman/listinfo/python-list
Re: How to reuse TCP listening socket immediately after it was connected at least once?
In article gvb8fn$7g...@lust.ihug.co.nz, Lawrence D'Oliveiro l...@geek-central.gen.new_zealand wrote: In message mailman.651.1243154739.8015.python-l...@python.org, Igor Katson wrote: I have written a socket server and some arbitrary clients. When I shutdown the server, and do socket.close(), I cannot immediately start it again cause it has some open sockets in TIME_WAIT state. It throws address already in use exception at me. There's a reason for that. It's to ensure that there are no leftover packets floating around the Internet somewhere, that you might mistakenly receive and think they were part of a new connection, when they were in fact part of an old one. In theory, that is indeed the reason for the TIME_WAIT state. In practice, however, using SO_REUSEADDR is pretty safe, and common practice. You've got several things working in your favor. First, late-delivery of packets is pretty rare. Second, if some late packet were to arrive, the chances of them having the same local and remote port numbers as an existing connection is slim. And, finally, the TCP sequence number won't line up. One thing to be aware of is that SO_REUSEADDR isn't 100% portable. There are some systems (ISTR HP-UX) which use SO_REUSEPORT instead of SO_REUSEADDR. The original specifications weren't very clear, and some implementers read them in strange ways. Some of that old code continues in use today. I only mention this because if you try SO_REUSEADDR and it's not doing what you expect, it's worth trying SO_REUSEPORT (or both) to see what happens on your particular system. The right thing to do is try to ensure that all your connections are properly closed at shutdown. That may not be enough (if your server crashes due to bugs), so the other thing you need to do is retry the socket open, say, at 30-second intervals, until it succeeds. That may be a reasonable thing to do for production code, but when you're building and debugging a server, it's a real pain to not be able to restart it quickly whenever you want (or need) to. -- http://mail.python.org/mailman/listinfo/python-list
Re: How to reuse TCP listening socket immediately after it was connected at least once?
Roy Smith wrote: In article gvb8fn$7g...@lust.ihug.co.nz, Lawrence D'Oliveiro l...@geek-central.gen.new_zealand wrote: In message mailman.651.1243154739.8015.python-l...@python.org, Igor Katson wrote: I have written a socket server and some arbitrary clients. When I shutdown the server, and do socket.close(), I cannot immediately start it again cause it has some open sockets in TIME_WAIT state. It throws address already in use exception at me. There's a reason for that. It's to ensure that there are no leftover packets floating around the Internet somewhere, that you might mistakenly receive and think they were part of a new connection, when they were in fact part of an old one. In theory, that is indeed the reason for the TIME_WAIT state. In practice, however, using SO_REUSEADDR is pretty safe, and common practice. You've got several things working in your favor. First, late-delivery of packets is pretty rare. Second, if some late packet were to arrive, the chances of them having the same local and remote port numbers as an existing connection is slim. And, finally, the TCP sequence number won't line up. One thing to be aware of is that SO_REUSEADDR isn't 100% portable. There are some systems (ISTR HP-UX) which use SO_REUSEPORT instead of SO_REUSEADDR. The original specifications weren't very clear, and some implementers read them in strange ways. Some of that old code continues in use today. I only mention this because if you try SO_REUSEADDR and it's not doing what you expect, it's worth trying SO_REUSEPORT (or both) to see what happens on your particular system. The right thing to do is try to ensure that all your connections are properly closed at shutdown. That may not be enough (if your server crashes due to bugs), so the other thing you need to do is retry the socket open, say, at 30-second intervals, until it succeeds. That may be a reasonable thing to do for production code, but when you're building and debugging a server, it's a real pain to not be able to restart it quickly whenever you want (or need) to. Thanks for a great answer, Roy! -- http://mail.python.org/mailman/listinfo/python-list
Re: How to reuse TCP listening socket immediately after it was connected at least once?
In message roy-3c4ded.09214724052...@news.panix.com, Roy Smith wrote: In article gvb8fn$7g...@lust.ihug.co.nz, Lawrence D'Oliveiro l...@geek-central.gen.new_zealand wrote: The right thing to do is try to ensure that all your connections are properly closed at shutdown. That may not be enough (if your server crashes due to bugs), so the other thing you need to do is retry the socket open, say, at 30-second intervals, until it succeeds. That may be a reasonable thing to do for production code, but when you're building and debugging a server, it's a real pain to not be able to restart it quickly whenever you want (or need) to. On the contrary, I run exactly the same logic--and that includes socket- handling logic--in both test and production servers. How else can I be sure it'll work properly in production? -- http://mail.python.org/mailman/listinfo/python-list
