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rust-libp2p/protocols
Roman Borschel d5c6370b15 Remove libp2p-ping keep-alive functionality. (#1067)
* Fix connection & handler shutdown when using `KeepAlive::Now`.

Delay::new(Instant::now()) is never immediately ready, resulting in
`KeepAlive::Now` to have no effect, since the delay is re-created on
every execution of `poll()` in the `NodeHandlerWrapper`. It can also
send the node handler into a busy-loop, since every newly
created Delay will trigger a task wakeup, which creates a new Delay
with Instant::now(), and so forth.

The use of `Delay::new(Instant::now())` for "immediate" connection shutdown
is therefore removed here entirely. An important assumption is thereby
that as long as the node handler non-empty `negotiating_in` and `negotiating_out`,
the handler is not dependent on such a Delay for task wakeup.

* Correction to the libp2p-ping connection timeout.

The current connection timeout is always short of one `interval`,
because the "countdown" begins with the last received or sent pong
(depending on the policy). In effect, the current default config has
a connection timeout of 5 seconds (20 - 15) from the point when a ping is sent.

Instead, the "countdown" of the connection timeout should always begin
with the next scheduled ping. That also makes all configurations valid,
avoiding pitfalls.

The important properties of the ping handler are now checked to hold for all
configurations, in particular:

  * The next ping must be scheduled no earlier than the ping interval
    and no later than the connection timeout.

  * The "countdown" for the connection timeout starts on the next ping,
    i.e. the full connection timeout remains at the instant when the
    next ping is sent.

* Do not keep connections alive.

The ping protocol is not supposed to keep otherwise idle connections
alive, only to add an additional condition for terminating them in
the form of a configurable number of consecutive failed ping requests.

In this context, the `PingPolicy` does not seem useful any longer.
2019-04-20 16:16:31 +02:00
..
2019-03-29 11:41:42 -03:00
2019-03-29 11:41:42 -03:00