From 4ebd9fb9901b9dbb29581e52fb2ff1eadfe6be76 2015-04-27 15:30:52
From: Lance Edgar <ledgar@sacfoodcoop.com>
Date: 2015-04-27 15:30:52
Subject: [PATCH] Add `PathNotFound` exception, normalize to it within `locking_copy_test()`.

Hopefully this improves the retry situation on a certain system I know...

---

diff --git a/rattail/exceptions.py b/rattail/exceptions.py
index 6c4c8d37f72a800a1da17fc7efcd2717910f0842..ab045316b57e58fa65c623ba1158206fe9a59710 100644
--- a/rattail/exceptions.py
+++ b/rattail/exceptions.py
@@ -2,7 +2,7 @@
 ################################################################################
 #
 #  Rattail -- Retail Software Framework
-#  Copyright © 2010-2014 Lance Edgar
+#  Copyright © 2010-2015 Lance Edgar
 #
 #  This file is part of Rattail.
 #
@@ -61,6 +61,32 @@ class RecipientsNotFound(ConfigurationError):
                 "(or 'default.to') in the [rattail.mail] section.".format(self.key))
 
 
+class FileOperationError(RattailError):
+    """
+    Generic exception for file operation failures.
+    """
+
+
+class PathNotFound(FileOperationError):
+    """
+    Raised when "path not found" errors are encountered within the
+    :func:`rattail.files.locking_copy_test()` function.  The purpose of this is
+    to normalize these errors to a single type, since the file monitor retry
+    mechanism will fail if two distinct exceptions are encountered during its
+    processing attempts.
+    """
+    def __init__(self, original_error):
+        self.original_error = original_error
+
+    def __str__(self):
+        return unicode(self).encode('utf_8')
+
+    def __unicode__(self):
+        return '{0}: {1}'.format(
+            self.original_error.__class__.__name__,
+            self.original_error)
+
+
 class BatchError(RattailError):
     """
     Base class for all batch-related errors.
diff --git a/rattail/files.py b/rattail/files.py
index 59b962454dbac577e60cdafe9a26df2c9550e436..4956aca487bea5f069fdb487845baad304e79b75 100644
--- a/rattail/files.py
+++ b/rattail/files.py
@@ -39,6 +39,8 @@ from datetime import datetime
 
 import pkg_resources
 
+from rattail.exceptions import PathNotFound
+
 
 def count_lines(path, encoding=None):
     """
@@ -135,16 +137,32 @@ def locking_copy_test(src, destdir):
     dst = os.path.join(destdir, fn)
     lockdir = '{0}.lock'.format(dst)
 
+    # Note that we normalize two separate errors to PathNotFound below.  This
+    # is because the file monitor retry mechanism will fail if two distinct
+    # error types are encountered.  Since this function needs to be somewhat
+    # robust in the face of network problems, raising a common error type will
+    # give us a better chance at being retried (if so configured).
+
     # Attempt to create the lock dir.  We ignore "file exists" error here since
     # it's possible this function may be called mutliple times as part of a
     # filemon retry strategy.
     try:
         os.mkdir(lockdir)
     except OSError as error:
+        if error.errno == errno.ENOENT:
+            raise PathNotFound(error)
         if error.errno != errno.EEXIST:
             raise
 
-    shutil.copy(src, dst)
+    # Attempt to copy the file.
+    try:
+        shutil.copy(src, dst)
+    except IOError as error:
+        if error.errno == errno.ENOENT:
+            raise PathNotFound(error)
+        raise
+
+    # Attempt to remove the lock dir.
     os.rmdir(lockdir)