* Remove redundant WrappedConnection
The matrix federation client uses an HTTP connection pool, which times out its
idle HTTP connections, so there is no need for any of this business.
* Correctly retry and back off if we get a HTTPerror response
* Refactor request sending to have better excpetions
MatrixFederationHttpClient blindly reraised exceptions to the caller
without differentiating "expected" failures (e.g. connection timeouts
etc) versus more severe problems (e.g. programming errors).
This commit adds a RequestSendFailed exception that is raised when
"expected" failures happen, allowing the TransactionQueue to log them as
warnings while allowing us to log other exceptions as actual exceptions.
- Improve logging: log things in the right order, include destination and txids
in all log lines, don't log successful responses twice
- Fix the docstring on TransportLayerClient.send_transaction
- Don't use treq.request, which is overcomplicated for our purposes: just use a
twisted.web.client.Agent.
- simplify the logic for setting up the bodyProducer
- fix bytes/str confusions
If a connection is lost before a request is read from Request, Twisted
sets `method` (and `uri`) attributes to dummy values. These dummy values
have incorrect types (i.e. they're not bytes), and so things like
`__repr__` would raise an exception.
To fix this we had a helper method to return the method with a
consistent type.
If a HTTP handler throws an exception while processing a request we
automatically write a JSON error response. If the handler had already
started writing a response twisted throws an exception.
We should check for this case and simple abort the connection if there
was an error after the response had started being written.
The existing deferred timeout helper function (and the one into twisted)
suffer from a bug when a deferred's canceller throws an exception, #3842.
The new helper function doesn't suffer from this problem.
We want to wait until we have read the response body before we log the request
as complete, otherwise a confusing thing happens where the request appears to
have completed, but we later fail it.
To do this, we factor the salient details of a request out to a separate
object, which can then keep track of the txn_id, so that it can be logged.
