PR #7445 incorrectly assumed that a peer that had already disconnected
and never reconnected was due to the endpoint client being dropped after
a successful socket shutdown. However, the issue at that time was that
there was not a single timeout guards that could cancel the `async_shutdown`
call, petentially blocking indefinetely. Although removing the client from
cache early might have allowed the endpoint to reconnect, it did not
resolve the underlying problem. Now that we have a proper cancellation
timeout, we can wait until the currently used socket is fully closed
before dropping the client from our cache. When our socket termination
works reliably, the `ApiListener` reconnect timer should attempt to
reconnect this endpoint after the next tick. Additionally, we now have
logs both for before and after socket termination, which may help
identify if it is hanging somewhere in between.
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.
Calling `AsioTlsStream::async_shutdown()` performs a TLS shutdown which
exchanges messages (that's why it takes a `yield_context`) and thus has the
potential to block the coroutine. Therefore, it should be protected with a
timeout. As `async_shutdown()` doesn't simply take a timeout, this has to be
implemented using a timer. So far, these timers are scattered throughout the
codebase with some places missing them entirely. This commit adds helper
functions to properly shutdown a TLS connection with a single function call.
The .ti files call `DependencyGraph::AddDependency(this, service.get())`. Obviously, `service.get()` is the parent and `this` (Downtime, Notification, ...) is the child. The DependencyGraph terminology should reflect this not to confuse its future users.
The following already works:
* Custom key sizes, e.g. 2048 bits
* Custom key types, e.g. ECC
* Multiple trusted root CAs in `/var/lib/icinga2/certs/ca.crt`
* Different root CAs per cluster subtree, as long as each node trusts the
issuers of the certificates of all nodes it's directly connected to
* Any number of intermediate CAs
