1 files changed, 104 insertions, 8 deletions
diff --git a/indra/llmessage/tests/testrunner.py b/indra/llmessage/tests/testrunner.py
index b70ce91ee7..f329ec2a0e 100644
--- a/indra/llmessage/tests/testrunner.py
+++ b/indra/llmessage/tests/testrunner.py
@@ -29,12 +29,109 @@ $/LicenseInfo$
 
 import os
 import sys
+import re
+import errno
+import socket
 
-def debug(*args):
-    sys.stdout.writelines(args)
-    sys.stdout.flush()
-# comment out the line below to enable debug output
-debug = lambda *args: None
+VERBOSE = os.environ.get("INTEGRATION_TEST_VERBOSE", "1") # default to verbose
+# Support usage such as INTEGRATION_TEST_VERBOSE=off -- distressing to user if
+# that construct actually turns on verbosity...
+VERBOSE = not re.match(r"(0|off|false|quiet)$", VERBOSE, re.IGNORECASE)
+
+if VERBOSE:
+    def debug(fmt, *args):
+        print fmt % args
+        sys.stdout.flush()
+else:
+    debug = lambda *args: None
+
+def freeport(portlist, expr):
+    """
+    Find a free server port to use. Specifically, evaluate 'expr' (a
+    callable(port)) until it stops raising EADDRINUSE exception.
+
+    Pass:
+
+    portlist: an iterable (e.g. xrange()) of ports to try. If you exhaust the
+    range, freeport() lets the socket.error exception propagate. If you want
+    unbounded, you could pass itertools.count(baseport), though of course in
+    practice the ceiling is 2^16-1 anyway. But it seems prudent to constrain
+    the range much more sharply: if we're iterating an absurd number of times,
+    probably something else is wrong.
+
+    expr: a callable accepting a port number, specifically one of the items
+    from portlist. If calling that callable raises socket.error with
+    EADDRINUSE, freeport() retrieves the next item from portlist and retries.
+
+    Returns: (expr(port), port)
+
+    port: the value from portlist for which expr(port) succeeded
+
+    Raises:
+
+    Any exception raised by expr(port) other than EADDRINUSE.
+
+    socket.error if, for every item from portlist, expr(port) raises
+    socket.error. The exception you see is the one from the last item in
+    portlist.
+
+    StopIteration if portlist is completely empty.
+
+    Example:
+
+    server, port = freeport(xrange(8000, 8010),
+                            lambda port: HTTPServer(("localhost", port),
+                                                    MyRequestHandler))
+    # pass 'port' to client code
+    # call server.serve_forever()
+    """
+    try:
+        # If portlist is completely empty, let StopIteration propagate: that's an
+        # error because we can't return meaningful values. We have no 'port',
+        # therefore no 'expr(port)'.
+        portiter = iter(portlist)
+        port = portiter.next()
+
+        while True:
+            try:
+                # If this value of port works, return as promised.
+                value = expr(port)
+
+            except socket.error, err:
+                # Anything other than 'Address already in use', propagate
+                if err.args[0] != errno.EADDRINUSE:
+                    raise
+
+                # Here we want the next port from portiter. But on StopIteration,
+                # we want to raise the original exception rather than
+                # StopIteration. So save the original exc_info().
+                type, value, tb = sys.exc_info()
+                try:
+                    try:
+                        port = portiter.next()
+                    except StopIteration:
+                        raise type, value, tb
+                finally:
+                    # Clean up local traceback, see docs for sys.exc_info()
+                    del tb
+
+            else:
+                debug("freeport() returning %s on port %s", value, port)
+                return value, port
+
+            # Recap of the control flow above:
+            # If expr(port) doesn't raise, return as promised.
+            # If expr(port) raises anything but EADDRINUSE, propagate that
+            # exception.
+            # If portiter.next() raises StopIteration -- that is, if the port
+            # value we just passed to expr(port) was the last available -- reraise
+            # the EADDRINUSE exception.
+            # If we've actually arrived at this point, portiter.next() delivered a
+            # new port value. Loop back to pass that to expr(port).
+
+    except Exception, err:
+        debug("*** freeport() raising %s: %s", err.__class__.__name__, err)
+        raise
 
 def run(*args, **kwds):
     """All positional arguments collectively form a command line, executed as
@@ -63,8 +160,7 @@ def run(*args, **kwds):
     # - [no p] don't use the PATH because we specifically want to invoke the
     #   executable passed as our first arg,
     # - [no e] child should inherit this process's environment.
-    debug("Running %s...\n" % (" ".join(args)))
-    sys.stdout.flush()
+    debug("Running %s...", " ".join(args))
     rc = os.spawnv(os.P_WAIT, args[0], args)
-    debug("%s returned %s\n" % (args[0], rc))
+    debug("%s returned %s", args[0], rc)
     return rc