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Prevent race during get_updates that can cause clients to miss messages 

This fixes #174

(imported from commit d900957e468815bcb99de67d570dfd7ce4413220)
This commit is contained in:
Zev Benjamin 2012-12-04 11:58:09 -05:00
parent f4898ea490
commit bc67d9d1d7
1 changed files with 20 additions and 0 deletions
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20
zephyr/views.py
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@ -443,6 +443,26 @@ def get_updates_backend(request, user_profile, handler, client_id,
if handler.request.connection.stream.closed():
return
try:
# It would be nice to be able to do this check in
# UserProfile.receive, but it doesn't know what the value
# of "last" was for each callback.
if last is not None and "messages" in cb_kwargs:
# We need to check whether there are any new messages
# between the client's get_updates call and the
# message we're about to return to the client and
# return them as well or the client will miss them.
# See #174.
messages = cb_kwargs["messages"]
extra_messages = (Message.objects.select_related()
.filter(usermessage__user_profile = user_profile,
id__gt = last,
id__lt = messages[0].id)
.order_by('id'))
if extra_messages:
new_messages = list(extra_messages)
new_messages.append(messages[0])
cb_kwargs["messages"] = new_messages
kwargs.update(cb_kwargs)
res = format_updates_response(user_profile=user_profile,
client_server_generation=client_server_generation,