Fix a bug in ``logcontext.preserve_fn`` which made it leak context into the
reactor, and add a test for it.
Also, get rid of ``logcontext.reset_context_after_deferred``, which tried to do
the same thing but had its own, different, set of bugs.
... and update some docstrings to correctly reflect the types being used.
get_new_device_msgs_for_remote can return a long under some circumstances,
which was being stored in last_device_list_stream_id_by_dest, and was then
upsetting things on the next loop.
Instead of calculating the size of the cache repeatedly, which can take
a long time now that it can use a callback, instead cache the size and
update that on insertion and deletion.
This requires changing the cache descriptors to have two caches, one for
pending deferreds and the other for the actual values. There's no reason
to evict from the pending deferreds as they won't take up any more
memory.
The debug 'full_twisted_stacktraces' flag caused synapse to rewrite
twisted deferreds to always fire the callback on the next reactor tick.
This was to force the deferred to always store the stacktraces on
exceptions, and thus be more likely to have a full stacktrace when it
reaches the final error handlers and gets printed to the logs.
Dynamically rewriting things is generally bad, and in particular this
change violates assumptions of various bits of Twisted. This wouldn't
necessarily be so bad, but it turns out this option has been turned on
on some production servers.
Turning the option can cause e.g. #1778.
For now, lets just entirely nuke this option.
This only makes a difference for versions of ldap3 before 1.0, but a)
its best to be explicit and b) there are distributions that package
ancient versions for ldap3 (e.g. debian).
Allows delegating the password auth to an external module. This also
moves the LDAP auth to using this system, allowing it to be removed from
the synapse tree entirely in the future.
