New CGI driver script that attempts to import the real script from the

Mailman.Cgi package.  Be as paranoid as possible about catching
exceptions and reporting them as HTML (which has saved my butt
numerous times already :-).

See the comments in the file for things that can still cause Server
errors.

1 files changed, 147 insertions, 0 deletions

diff --git a/scripts/driver b/scripts/driver
new file mode 100644
index 000000000..fc2b59a4e
--- /dev/null
+++ b/scripts/driver
@@ -0,0 +1,147 @@
+#! /usr/bin/env python
+#
+# Copyright (C) 1998 by the Free Software Foundation, Inc.
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation; either version 2
+# of the License, or (at your option) any later version.
+# 
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+# 
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software 
+# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+
+
+
+# This standard driver script is used to run CGI programs, wrapped in code
+# that catches errors, and displays them as HTML.  This guarantees that
+# (almost) any problems in the Mailman software doesn't result in a Web server
+# error.  It is much more helpful to generate and show a traceback, which the
+# user could send to the administrator, than to display a server error and
+# have to trudge through server logs.
+
+# Note: this isn't 100% perfect!  Here are some things that can go wrong that
+# are not caught and reported as traceback-containing HTML:
+#
+# - This file could contain a syntax error.  In that case, you would indeed
+#   get a Web server error since this file wouldn't even compile, and there's
+#   no way to catch that.
+#
+# - The sys module could be royally screwed.  Either we couldn't import it, or 
+#   it didn't have a sys.stderr attribute.  Both those would indicate serious
+#   problems in the Python installation.  These won't generate Web server
+#   errors, but neither will they give meaningful tracebacks.
+#
+# - We couldn't import the traceback module, or traceback.print_exc()
+#   failed.  Same diagnosis and effect as with sys being broken.
+#
+# I consider all these pretty unlikely.  Note that it is also possible that
+# the environment variables wouldn't be printed, perhaps because os couldn't
+# be imported or there was some problem with os.environ.  Again, not likely.
+
+
+
+def run_main():
+    try:
+        # insert the relative path to the parent of the Mailman package
+        # directory, so we can pick up the Utils module
+        import os
+        sys.path.insert(0, os.pardir)
+        # map stderr to a logger, if possible
+        import Mailman.Utils
+        try:
+            sys.stderr = Utils.StampedLogger('error', label='admin',
+                                             manual_reprime=1,
+                                             nofail=0)
+        except:
+            # semi-bogus bare except means that if any problems in creating
+            # the logger occur, we should just use standard stderr
+            pass
+        #
+        # The name of the module to run is passed in argv[1].  What we
+        # actually do is import the module named by argv[1] that lives in the
+        # Mailman.Cgi package.  That module must have a main() function, which
+        # we dig out and call.
+        #
+        scriptname = sys.argv[1]
+        # See the reference manual for why we have to do things this way.
+        # Note that importing should have no side-effects!
+        pkg = __import__('Mailman.Cgi', globals(), locals(), [scriptname])
+        module = getattr(pkg, scriptname)
+        main = getattr(module, 'main')
+        try:
+            main()
+        except SystemExit:
+            # this is a valid way for the function to exit
+            pass
+    except:
+        print_traceback()
+        print_environment()
+
+
+
+def print_traceback():
+    print """\
+Content-type: text/html
+
+<p><h3>We're sorry, we hit a bug!</h3>
+
+<p>If you would like to help us identify the problem, please
+email a copy of this page to the webmaster for this site with
+a description of what happened.  Thanks!
+
+<h4>Traceback:</h4>
+<p><pre>
+"""
+    try:
+        import traceback
+        traceback.print_exc(file=sys.stdout)
+    except:
+        print '[failed to get a traceback]'
+    print '\n\n</pre>'
+
+
+
+def print_environment():
+    try:
+        import os
+        print '''\
+<p><hr><h4>Environment variables:</h4>
+
+<p><table>
+<tr><td><strong>Variable</strong></td>
+<td><strong>Value</strong></td></tr>
+'''
+        for varname, value in os.environ.items():
+            print '<tr><td>', varname, '</td><td>', value, '</td></tr>'
+        print '</table>'
+    except:
+        print '<p><hr>[environment variables are not available]'
+
+
+try:
+    import sys
+    # cache so we can undo this, even though it's probably not strictly
+    # necessary since the script is exiting soon anyway
+    stderr = sys.stderr
+    try:
+        run_main()
+    finally:
+        sys.stderr = stderr
+except:
+    # Jeez, we couldn't even import sys, or sys didn't have a stderr
+    # attribute!
+    print """\
+Content-type: text/html
+
+<p><h3>We're sorry, we hit a bug!</h3>
+
+Mailman experienced a very low level failure and could not even generate
+a useful traceback.  Please report this to the Mailman administrator at
+this site.
+"""