node.py: raise RLIMIT_NOFILE on bsd/cygwin to more than 256

src/allmydata/node.py

@@ -1,5 +1,5 @@
 
-import datetime, os.path, re, types
+import datetime, os.path, re, types, resource
 from base64 import b32decode, b32encode
 
 import twisted
@@ -75,6 +75,52 @@ class Node(service.MultiService):
                  " twisted: %s, zfec: %s"
                  % (allmydata.__version__, foolscap.__version__,
                     twisted.__version__, zfec.__version__,))
+        self.increase_rlimits()
+
+    def increase_rlimits(self):
+        # We'd like to raise our soft resource.RLIMIT_NOFILE, since certain
+        # systems (OS-X, probably solaris) start with a relatively low limit
+        # (256), and some unit tests want to open up more sockets than this.
+        # Most linux systems start with both hard and soft limits at 1024,
+        # which is plenty.
+
+        # unfortunately the values to pass to setrlimit() vary widely from
+        # one system to another. OS-X reports (256, HUGE), but the real hard
+        # limit is 10240, and accepts (-1,-1) to mean raise it to the
+        # maximum. Cygwin reports (256, -1), then ignores a request of
+        # (-1,-1): instead you have to guess at the hard limit (it appears to
+        # be 3200), so using (3200,-1) seems to work. Linux reports a
+        # sensible (1024,1024), then rejects (-1,-1) as trying to raise the
+        # maximum limit, so you could set it to (1024,1024) but you might as
+        # well leave it alone.
+
+        try:
+            current = resource.getrlimit(resource.RLIMIT_NOFILE)[0]
+        except AttributeError:
+            # we're probably missing RLIMIT_NOFILE, maybe this is windows
+            return
+
+        if current >= 1024:
+            # good enough, leave it alone
+            return
+
+        try:
+            # this one works on OS-X (bsd), and gives us 10240, but
+            # it doesn't work on linux (on which both the hard and
+            # soft limits are set to 1024 by default).
+            resource.setrlimit(resource.RLIMIT_NOFILE, (-1,-1))
+            new = resource.getrlimit(resource.RLIMIT_NOFILE)[0]
+            if new == current:
+                # probably cygwin, which ignores -1. Use a real value.
+                resource.setrlimit(resource.RLIMIT_NOFILE, (3200,-1))
+
+        except ValueError:
+            self.log("unable to set RLIMIT_NOFILE: current value %s"
+                     % (resource.getrlimit(resource.RLIMIT_NOFILE),))
+        except:
+            # who knows what. It isn't very important, so log it and continue
+            log.err()
+
 
     def get_config(self, name, mode="r", required=False):
         """Get the (string) contents of a config file, or None if the file