[PATCH] Protect IMAP.getmessage() against dropped connections

[Sebastian Spaeth]

If a connection is dropped for some reason while fetching a message, the
imapobj.uid command throws an imapbj.abort() Exception which means we are
supposed to retry. Implement a fail loop that drops the connection, gets a
new one and attempts the command another time.

Remove obsolete comment that we need to catch nonexisting messages. We do
now.

GMail seems to drop connections left and right. This patch is a response to
the reported mail "4E5F8D8C.1020005 at gmail.com" by zeek
<ezekiel.das at gmail.com>.

Signed-off-by: Sebastian Spaeth <Sebastian at SSpaeth.de>
---
This patch protects the getmessage() call against dropped connections
and retres (once) if a connection has been dropped. It seems Gmail drops
connections all the time, as the previous select() succeeded. Any
comments.

 offlineimap/folder/IMAP.py |   27 +++++++++++++++------------
 1 files changed, 15 insertions(+), 12 deletions(-)

diff --git a/offlineimap/folder/IMAP.py b/offlineimap/folder/IMAP.py
index dec14ae..ac18d69 100644
--- a/offlineimap/folder/IMAP.py
+++ b/offlineimap/folder/IMAP.py
@@ -207,8 +207,21 @@ class IMAPFolder(BaseFolder):
         """
         imapobj = self.imapserver.acquireconnection()
         try:
-            imapobj.select(self.getfullname(), readonly = 1)
-            res_type, data = imapobj.uid('fetch', str(uid), '(BODY.PEEK[])')
+            fails_left = 2 # retry on dropped connection
+            while fails_left:
+                try:
+                    imapobj.select(self.getfullname(), readonly = 1)
+                    res_type, data = imapobj.uid('fetch', str(uid),
+                                                 '(BODY.PEEK[])')
+                    fails_left = 0
+                except imapobj.abort(), e:
+                    # Release dropped connection, and get a new one
+                    self.imapserver.releaseconnection(imapobj)
+                    imapobj = self.imapserver.acquireconnection()
+                    self.ui.error(e, exc_info()[2])
+                    fails_left -= 1
+                    if not fails_left:
+                        raise e
             if data == [None] or res_type != 'OK':
                 #IMAP server says bad request or UID does not exist
                 severity = OfflineImapError.ERROR.MESSAGE
@@ -223,16 +236,6 @@ class IMAPFolder(BaseFolder):
             # data looks now e.g. [('320 (UID 17061 BODY[]
             # {2565}','msgbody....')]  we only asked for one message,
             # and that msg is in data[0]. msbody is in [0][1]
-
-            #NB & TODO: When the message on the IMAP server has been
-            #deleted in the mean time, it will respond with an 'OK'
-            #res_type, but it will simply not send any data. This will
-            #lead to a crash in the below line. We need urgently to
-            #detect this, protect from this and need to think about what
-            #to return in this case. Probably returning `None` in this
-            #case would be good. But we need to make sure that all
-            #Backends behave the same, and that we actually check the
-            #return value and behave accordingly.
             data = data[0][1].replace("\r\n", "\n")
 
             if len(data)>200:
-- 
1.7.4.1