Fixed race condition on import in errorcodes.lookup

Fixes #382.

NEWS

@@ -27,6 +27,7 @@ What's new in psycopg 2.6.2
 - Raise `!NotSupportedError` on unhandled server response status
   (:ticket:`#352`).
 - Fixed `!PersistentConnectionPool` on Python 3 (:ticket:`#348`).
+- Fixed `!errorcodes.lookup` initialization thread-safety (:ticket:`#382`).
 
 
 What's new in psycopg 2.6.1

lib/errorcodes.py

@@ -38,11 +38,17 @@ def lookup(code, _cache={}):
         return _cache[code]
 
     # Generate the lookup map at first usage.
+    tmp = {}
     for k, v in globals().iteritems():
         if isinstance(v, str) and len(v) in (2, 5):
-            _cache[v] = k
+            tmp[v] = k
 
-    return lookup(code)
+    assert tmp
+
+    # Atomic update, to avoid race condition on import (bug #382)
+    _cache.update(tmp)
+
+    return _cache[code]
 
 
 # autogenerated data: do not edit below this point.

tests/__init__.py

@@ -34,6 +34,7 @@ import test_connection
 import test_copy
 import test_cursor
 import test_dates
+import test_errcodes
 import test_extras_dictcursor
 import test_green
 import test_lobject
@@ -71,6 +72,7 @@ def test_suite():
     suite.addTest(test_copy.test_suite())
     suite.addTest(test_cursor.test_suite())
     suite.addTest(test_dates.test_suite())
+    suite.addTest(test_errcodes.test_suite())
     suite.addTest(test_extras_dictcursor.test_suite())
     suite.addTest(test_green.test_suite())
     suite.addTest(test_lobject.test_suite())

tests/test_errcodes.py

@@ -0,0 +1,65 @@
+#!/usr/bin/env python
+
+# test_errcodes.py - unit test for psycopg2.errcodes module
+#
+# Copyright (C) 2015 Daniele Varrazzo  <daniele.varrazzo@gmail.com>
+#
+# psycopg2 is free software: you can redistribute it and/or modify it
+# under the terms of the GNU Lesser General Public License as published
+# by the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# In addition, as a special exception, the copyright holders give
+# permission to link this program with the OpenSSL library (or with
+# modified versions of OpenSSL that use the same license as OpenSSL),
+# and distribute linked combinations including the two.
+#
+# You must obey the GNU Lesser General Public License in all respects for
+# all of the code used other than OpenSSL.
+#
+# psycopg2 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 Lesser General Public
+# License for more details.
+
+from testutils import unittest, ConnectingTestCase
+
+try:
+    reload
+except NameError:
+    from imp import reload
+
+from threading import Thread
+from psycopg2 import errorcodes
+
+class ErrocodeTests(ConnectingTestCase):
+    def test_lookup_threadsafe(self):
+
+        # Increase if it does not fail with KeyError
+        MAX_CYCLES = 2000
+
+        errs = []
+        def f(pg_code='40001'):
+            try:
+                errorcodes.lookup(pg_code)
+            except Exception, e:
+                errs.append(e)
+
+        for __ in xrange(MAX_CYCLES):
+            reload(errorcodes)
+            (t1, t2) = (Thread(target=f), Thread(target=f))
+            (t1.start(), t2.start())
+            (t1.join(), t2.join())
+
+            if errs:
+                self.fail(
+                    "raised %s errors in %s cycles (first is %s %s)" % (
+                        len(errs), MAX_CYCLES,
+                        errs[0].__class__.__name__, errs[0]))
+
+
+def test_suite():
+    return unittest.TestLoader().loadTestsFromName(__name__)
+
+if __name__ == "__main__":
+    unittest.main()