The wait group gets passed to HttpServerConnection, then down to the
HttpHandlers. For those handlers that modify the program state, the
wait group is locked so ApiListener will wait on Stop() for the
request to complete. If the request iterates over config objects,
a further check on the state of the wait group is added to abort early
and not delay program shutdown. In that case, 503 responses will be
sent to the client.
Additionally, in HttpServerConnection, no further requests than the
one already started will be allowed once the wait group is joining.
Pin child objects of hosts (HOST!...) to the same endpoint as the host.
This reduces cross-object action latency withing the same host.
If all endpoints know this algorithm, we can use it.
It's not used. Also, the callback shall run completely at once. This ensures that it won't (continue to) run once another coroutine on the strand calls Timeout#Cancel().
The reason for introducing AsioTlsStream::GracefulDisconnect() was to handle
the TLS shutdown properly with a timeout since it involves a timeout. However,
the implementation of this timeout involves spwaning coroutines which are
redundant in some cases. This commit adds comments to the remaining calls of
async_shutdown() stating why calling it is safe in these places.
Something is definitely going wrong if a client tries to reconnect to
this endpoint while it still has an active connection to that client. So
we shouldn't hide this, but at least log it at info level. Apart from
that, I've added some additional information about the currently active
client, such as when the last message was sent and received.
Closing and re-opening that very same log file shouldn't reset the
counter, otherwise some log files may exceed the max limit per file as
their offset indicator is reset each time they are re-opened.
On incoming connection timeout we log the remote endpoint which isn't
available if it was already disconnected - an exception is thrown. Get it
as long as we're still connected not to lose it, nor to get an exception.
If a connection hangs for too long in ApiListener#NewClientHandler(),
ApiListener#AddConnection()'s Timeout calls boost::asio::basic_socket#cancel()
on that connection to trigger an exception which unwinds
ApiListener#NewClientHandler(). Previously that unwind could trigger a Defer
which called boost::asio::ssl::stream#async_shutdown() which extended the hang.
