[Mono-bugs] [Bug 71203][Wis] New - Many Socket Methods Fail when > 1024 File descriptors are Open

bugzilla-daemon@bugzilla.ximian.com bugzilla-daemon@bugzilla.ximian.com
Wed, 12 Jan 2005 11:21:33 -0500 (EST)

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Changed by scott@imeem.com.


--- shadow/71203	2005-01-12 11:21:33.000000000 -0500
+++ shadow/71203.tmp.11731	2005-01-12 11:21:33.000000000 -0500
@@ -0,0 +1,49 @@
+Bug#: 71203
+Product: Mono: Class Libraries
+Version: 1.1
+OS: Red Hat 9.0
+OS Details: 
+Status: NEW   
+Priority: Wishlist
+Component: CORLIB
+AssignedTo: mono-bugs@ximian.com                            
+ReportedBy: scott@imeem.com               
+QAContact: mono-bugs@ximian.com
+TargetMilestone: ---
+Summary: Many Socket Methods Fail when > 1024 File descriptors are Open
+Please fill in this template when reporting a bug, unless you know what you are doing.
+Description of Problem:
+When many sockets and files are open it's easy to exceed the 1024 limit imposed by the select() 
+system call, this system call is used by a number of methods in the socket class and also many 
+other parts of System.Net & System.Net.Sockets
+Steps to reproduce the problem:
+1.  Open many sockets and filed
+2. Poll the sockets for activity, the polls will begin to fail when their underlying file descriptor is 
+> 1024
+Actual Results:
+Things go wrong in various interesting ways.
+Expected Results:
+The .Net documentation does not mention any limits for open file descriptors and related socket 
+How often does this happen? 
+Whenever anyone writes a server which handles thousands of clients.
+Additional Information:
+Mono under the hood uses select() in a few places, this will ultimately fail if it's asked to select on 
+a file descriptor with an ID > 1024, most modern unix systems provide the poll() system call 
+which provides similar functionality without the limit. Mono should detect at build time whether 
+poll() will be available on the target platform and use it instead of select().
+This limit makes it surprisingly hard to write servers which handle thousands of connections (and 
+if you ask any .Net guru they'll chastise you for not using the Async methods - on every mono 
+install I've tried they lock up with > 25 pending operations)