Oops, we were being overzealous about calling nowrite().

We were doing it as soon as the other end was shut_read, but we didn't
confirm first that the other end's read buffer had been totally emptied.
This caused problems on twitter.com, at least, where they create a zillion
short-lived connections.

I don't actually need these lines at all, as it turns out, because we were
already calling nowrite() correctly on the other end after a buffer got
emptied.

ssnet.py

@@ -151,7 +151,7 @@ class SockWrapper:
             try:
                 self.wsock.shutdown(SHUT_WR)
             except socket.error, e:
-                self.seterr(e)
+                self.seterr('nowrite: %s' % e)
 
     def too_full(self):
         return False  # fullness is determined by the socket's select() state
@@ -163,9 +163,14 @@ class SockWrapper:
         try:
             return _nb_clean(os.write, self.wsock.fileno(), buf)
         except OSError, e:
-            # unexpected error... stream is dead
-            self.seterr(e)
-            return 0
+            if e.errno == errno.EPIPE:
+                debug1('%r: uwrite: got EPIPE\n' % self)
+                self.nowrite()
+                return 0
+            else:
+                # unexpected error... stream is dead
+                self.seterr('uwrite: %s' % e)
+                return 0
         
     def write(self, buf):
         assert(buf)
@@ -180,7 +185,7 @@ class SockWrapper:
         try:
             return _nb_clean(os.read, self.rsock.fileno(), 65536)
         except OSError, e:
-            self.seterr(e)
+            self.seterr('uread: %s' % e)
             return '' # unexpected error... we'll call it EOF
 
     def fill(self):
@@ -232,9 +237,7 @@ class Proxy(Handler):
         self.wrap2 = wrap2
 
     def pre_select(self, r, w, x):
-        if self.wrap1.shut_read: self.wrap2.nowrite()
         if self.wrap1.shut_write: self.wrap2.noread()
-        if self.wrap2.shut_read: self.wrap1.nowrite()
         if self.wrap2.shut_write: self.wrap1.noread()
         
         if self.wrap1.connect_to: