Rather than have three methods which have to have the same interface,
factor out a separate interface which is provided by three implementations.
I find it easier to grok the code this way.
This is a first step to checking that the key is valid at the required moment.
The idea here is that, rather than passing VerifyKey objects in and out of the
storage layer, we instead pass FetchKeyResult objects, which simply wrap the
VerifyKey and add a valid_until_ts field.
* Pass time_added_ms into process_v2_response
* Simplify process_v2_response
We can merge old_verify_keys into verify_keys, and reduce the number of dicts
flying around.
Storing server keys hammered the database a bit. This replaces the
implementation which stored a single key, with one which can do many updates at
once.
There's no point in collecting a merged dict of keys: it is sufficient to
consider just the new keys which have been fetched by the most recent
key_fetch_fns.
Make this just return the key dict, rather than a single-entry dict mapping the
server name to the key dict. It's easy for the caller to get the server name
from from the response object anyway.
This is in preparation for making EventBuilder format agnostic, which
means event signing should be done against the event dict rather than
the EventBuilder object.
The problem here is that we have cut-and-pasted an impl from Twisted, and then
failed to maintain it. It was fixed in Twisted in
https://github.com/twisted/twisted/pull/1047/files; let's do the same here.
Broadly three things here:
* disable W504 which seems a bit whacko
* remove a bunch of `as e` expressions from exception handlers that don't use
them
* use `r""` for strings which include backslashes
Also, we don't use pep8 any more, so we can get rid of the duplicate config
there.
Firstly, don't swallow the reason for the failure
Secondly, don't assume all exceptions are verification failures
Thirdly, log a bit of info about the key being used if debug is enabled
While I was going through uses of preserve_fn for other PRs, I converted places
which only use the wrapped function once to use run_in_background, to avoid
creating the function object.
There were a bunch of places where we fire off a process to happen in the
background, but don't have any exception handling on it - instead relying on
the unhandled error being logged when the relevent deferred gets
garbage-collected.
This is unsatisfactory for a number of reasons:
- logging on garbage collection is best-effort and may happen some time after
the error, if at all
- it can be hard to figure out where the error actually happened.
- it is logged as a scary CRITICAL error which (a) I always forget to grep for
and (b) it's not really CRITICAL if a background process we don't care about
fails.
So this is an attempt to add exception handling to everything we fire off into
the background.
