[MERGE][bug #153786] Partial fix for retrying if a pack file disappears

[Martin Pool]

Martin Pool has voted tweak.
Status is now: Conditionally approved
Comment:
Thanks for fixing this.

I wonder if we should do something to prevent it looping indefinitely 
while
retrying, but that's probably unlikely and yagni; we can deal with it if 
it
arises.

The implementation looks correct and nicely tested.

=== modified file 'NEWS'
--- NEWS        2008-10-21 20:49:54 +0000
+++ NEWS        2008-10-23 21:06:43 +0000
@@ -44,6 +44,11 @@
        could only happen if ``bzr reconcile`` decided that the parent
        ordering was incorrect in the file graph.  (John Arbash Meinel)

+    * The index logic is now able to reload the list of pack files if 
and
+      index ends up disappearing. We still don't reload if the pack 
data
+      itself goes missing after checking the index.
+      (John Arbash Meinel, #153786)
+
    DOCUMENTATION:


To make it more clear which bug this is maybe add

   This fixes where operations on a repository transiently fail with 
'file not found'
   when another process is writing to that repository.

or something similar.

    API CHANGES:

=== modified file 'bzrlib/index.py'
--- bzrlib/index.py     2008-09-21 14:48:37 +0000
+++ bzrlib/index.py     2008-10-23 20:53:50 +0000
@@ -27,6 +27,7 @@
  from bisect import bisect_right
  from cStringIO import StringIO
  import re
+import sys

  from bzrlib.lazy_import import lazy_import
  lazy_import(globals(), """
@@ -1106,12 +1107,16 @@
      in the index list.
      """

-    def __init__(self, indices):
+    def __init__(self, indices, reload_func=None):
          """Create a CombinedGraphIndex backed by indices.

          :param indices: An ordered list of indices to query for data.
+        :param reload_func: A function to call if we find we are 
missing an
+            index. Should have the form reload_func() => True/False to 
indicate
+            if reloading actually changed anything.

It wasn't clear to me from this description that 'changed anything' 
means 'we
have a chance to now find the indexes'.  I thought maybe you meant if it
changed some cached state.

+    def _reload_or_raise(self):
+        """We just got a NoSuchFile exception.
+
+        Try to reload the indices, if it fails, just raise the current
+        exception.
+        """
+        if self._reload_func is None:
+            raise
+        exc_type, exc_value, exc_traceback = sys.exc_info()
+        if not self._reload_func():
+            # We tried to reload, but nothing changed, so we fail 
anyway
+            raise exc_type, exc_value, exc_traceback

I would have put a guarded mutter statement here.

--
Martin


For details, see: 
http://bundlebuggy.aaronbentley.com/project/bzr/request/%3C4900E912.3030502%40arbash-meinel.com%3E
Project: Bazaar