Race condition while buddy initiation

[alsroot]

The problem is that right after becoming online, buddy (jabber user) is in inconsistent state before all pep (​http://xmpp.org/extensions/xep-0163.html) properties will be published on jabber server.

[alsroot]

Attached patch is a workaround that shows the affected place in sugar shell code.

[sascha_silbe]

We should probably call ​SetProperties right after creating the connection in ​jarabe.model.neighborhood._Account._prepare_connection(), not in ​__connection_ready_cb() after the connection has been established.

Nevertheless Sugar should cope with this race condition on the receiver side. As PEP is used we should get notified of the properties as soon as the sender publishes them (​PropertiesChanged signal, ​__buddy_info_updated_cb()).

If I grok the code right, this should be race-free: The signal callbacks get set up in ​__get_self_handle_cb(), as part of the callback for the Status call in ​__connection_ready_cb(). The ​GetProperties call happens in ​_update_buddy_activities() and ​__get_contact_attributes_cb(), both times only in response to the signals we subscribed to in ​__get_self_handle_cb():

• ​MembersChanged signal -> ​__members_changed_cb() -> ​_add_buddy_handles() -> ​GetContactAttributes -> ​__get_contact_attributes_cb()
• ​ActivitiesChanged signal -> ​__buddy_activities_changed_cb()
• ​ActivityPropertiesChanged signal -> ​__activity_properties_changed_cb() -> ​_update_activity() -> ​GetActivities -> ​__got_activities_cb()
• ​MembersChanged signal -> ​__members_changed_cb() -> ​_add_buddy_handles() -> ​GetContactAttributes -> ​__get_contact_attributes_cb() -> ​GetActivities -> ​__got_activities_cb()

We should consider the use case of non-Sugar buddies when fixing the receiver side of this bug: When ​GetProperties fails, it can be due to this bug (​SetProperties called too late on the sender side) or because the buddy isn't running Sugar. We should be able to distinguish these two cases by examining the ​capabilities (see ​PEP: Filtered Notifications). In the non-Sugar case we should show the buddy right away. For Sugar buddies we might want to wait for the ​PropertiesChanged signal, potentially forever.