When we get a federation request which refers to an event id, make sure that
said event is in the room the caller claims it is in.
(patch supplied by @turt2live)
This commit replaces SynapseError.from_http_response_exception with
HttpResponseException.to_synapse_error.
The new method actually returns a ProxiedRequestError, which allows us to pass
through additional metadata from the API call.
We really shouldn't be sending all CodeMessageExceptions back over the C-S API;
it will include things like 401s which we shouldn't proxy.
That means that we need to explicitly turn a few HttpResponseExceptions into
SynapseErrors in the federation layer.
The effect of the latter is that the matrix errcode will get passed through
correctly to calling clients, which might help with some of the random
M_UNKNOWN errors when trying to join rooms.
This fixes#3518, and ensures that we get useful logs and metrics for lots of
things that happen in the background.
(There are certainly more things that happen in the background; these are just
the common ones I've found running a single-process synapse locally).
This introduces a mechanism for tracking resource usage by background
processes, along with an example of how it will be used.
This will help address #3518, but more importantly will give us better insights
into things which are happening but not being shown up by the request metrics.
We *could* do this with Measure blocks, but:
- I think having them pulled out as a completely separate metric class will
make it easier to distinguish top-level processes from those which are
nested.
- I want to be able to report on in-flight background processes, and I don't
think we want to do this for *all* Measure blocks.
We need to do a bit more validation when we get a server name, but don't want
to be re-doing it all over the shop, so factor out a separate
parse_and_validate_server_name, and do the extra validation.
Also, use it to verify the server name in the config file.
Make sure that server_names used in auth headers are sane, and reject them with
a sensible error code, before they disappear off into the depths of the system.
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.
