Re: [undertow-dev] Too many open files: Exception accepting request, closing server channel TCP server (NIO)

On Mon, Mar 2, 2020 at 7:56 AM Stan Rosenberg <stan.rosenberg(a)acm.org&gt; wrote: > > Stuck in CLOSE_WAIT is a symptom of the client-side not properly shutting down [1]. I would partially disagree. In the article you linked: "It all starts with a listening application that leaks sockets and forgets to call close(). This kind of bug does happen in complex applications." This seems to be essentially what's happening here: the server isn't completing the connection (for some reason), stranding the socket in `CLOSE_WAIT`. We can't assume that the client is abandoning the connection after `FIN_WAIT2` (the titular RFC violation); if the server stays in `CLOSE_WAIT`, then even if the client dutifully stays in `FIN_WAIT2` forever, the resolving condition still needs to be that the server shuts down its side of the connection. This diagram is a useful visual aid, mapping TCP states to the XNIO API: https://www.lucidchart.com/publicSegments/view/524ec20a-5c40-4fd0-8bde-0a... -- - DML