BIND 10 trac2410, updated. 9f454868d6240a3113bed21cd719293ddb10991f [2410] Attempt to fix race condition in test

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       via  9f454868d6240a3113bed21cd719293ddb10991f (commit)
      from  ac0d3badda51a5bb268e92ee3d0f61a5ce519f12 (commit)

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- Log -----------------------------------------------------------------
commit 9f454868d6240a3113bed21cd719293ddb10991f
Author: Stephen Morris <stephen at isc.org>
Date:   Wed Nov 21 18:03:04 2012 +0000

    [2410] Attempt to fix race condition in test
    
    Attempts to fix a process/subprocess race condition by having
    the parent process loop waiting for output instead of assuming
    that the subprocess has started and has written something by the
    time it gets round to reading it.
    
    Also closes a few unclosed file descriptors at the end of a test.

-----------------------------------------------------------------------

Summary of changes:
 src/bin/dhcp6/tests/dhcp6_test.py |   75 ++++++++++++++++++++++++-------------
 1 file changed, 48 insertions(+), 27 deletions(-)

-----------------------------------------------------------------------
diff --git a/src/bin/dhcp6/tests/dhcp6_test.py b/src/bin/dhcp6/tests/dhcp6_test.py
index f3099b9..d82d513 100644
--- a/src/bin/dhcp6/tests/dhcp6_test.py
+++ b/src/bin/dhcp6/tests/dhcp6_test.py
@@ -89,45 +89,66 @@ class TestDhcpv6Daemon(unittest.TestCase):
         fl = fcntl.fcntl(fd, fcntl.F_GETFL)
         fcntl.fcntl(fd, fcntl.F_SETFL, fl | os.O_NONBLOCK)
 
-        # There's potential problem if b10-dhcp4 prints out more
-        # than 16k of text
-        try:
-            output = os.read(self.stdout_pipes[0], 16384)
-        except OSError:
-            print("No data available from stdout")
-            output = ""
-
-        # read can return None. Make sure we have a string
-        if (output is None):
-            output = ""
-
-        try:
-            error = os.read(self.stderr_pipes[0], 16384)
-        except OSError:
-            print("No data available on stderr")
-            error = ""
-
-        # read can return None. Make sure we have a string
-        if (error is None):
-            error = ""
-
-        try:
-            if (not pi.process.poll()):
-                # let's be nice at first...
+        # As we don't know how long the subprocess will take to start and
+        # produce output, we'll loop and sleep for 250ms between each
+        # iteration.  To avoid an infinite loop, we'll loop for a maximum
+        # of five seconds: that should be enough.
+        count = 20
+        output = ""
+        error = ""
+        while count > 0:
+            try:
+                new_output = os.read(self.stdout_pipes[0], 16384)
+            except OSError:
+                new_output = ""
+
+            # read can return None. Make sure we have a string
+            if (new_output is not None):
+                output = output + str(new_output)
+
+            try:
+                new_error = os.read(self.stderr_pipes[0], 16384)
+            except OSError:
+                new_error = ""
+
+            # read can return None. Make sure we have a string
+            if (new_error is not None):
+                error = error + str(new_error)
+
+            # If the process has already exited, or if it has output something,
+            # quit the loop now.
+            if pi.process.poll() is not None or len(error) > 0 or len(output) > 0:
+                break
+
+            # Process still running, try again in 250 ms.
+            count = count - 1
+            time.sleep(0.25)
+
+        # Exited loop, kill the process if it is still running
+        if pi.process.poll() is None:
+            try:
                 pi.process.terminate()
-        except OSError:
-            print("Ignoring failed kill attempt. Process is dead already.")
+            except OSError:
+                print("Ignoring failed kill attempt. Process is dead already.")
 
         # call this to get returncode, process should be dead by now
         rc = pi.process.wait()
 
         # Clean up our stdout/stderr munging.
         os.dup2(self.stdout_old, sys.stdout.fileno())
+        os.close(self.stdout_old)
         os.close(self.stdout_pipes[0])
 
         os.dup2(self.stderr_old, sys.stderr.fileno())
+        os.close(self.stderr_old)
         os.close(self.stderr_pipes[0])
 
+        # Free up resources (file descriptors) from the ProcessInfo object
+        # TODO: For some reason, this gives an error if the process has ended,
+        #       although it does cause all descriptors still allocated to the
+        #       object to be freed.
+        pi = None
+
         print ("Process finished, return code=%d, stdout=%d bytes, stderr=%d bytes"
                % (rc, len(output), len(error)) )