He-Pin opened a new issue, #3246:
URL: https://github.com/apache/pekko/issues/3246
### Description
`TcpOutgoingConnection` leaks the `SocketChannel` file descriptor when the
connection setup fails before the `ChannelRegistration` message is received
from the selector.
### Root cause
In `TcpOutgoingConnection.scala` (lines 54-72), the `SocketChannel` is
opened in the constructor (line 44) before the actor starts processing
messages. If any operation before `channelRegistry.register()` throws (e.g., a
user-provided `SocketOption.beforeConnect`), `reportConnectFailure` catches the
exception and calls `stop(e)`.
At this point, `registration` is still `None` because the
`ChannelRegistration` message has not been received yet.
In `TcpConnection.stopWith` (lines 390-404):
```scala
registration match {
case None =>
context.stop(self) // channel NOT closed!
case Some(reg) =>
context.become(unregistering)
reg.cancelAndClose(() => self ! Unregistered) // channel IS closed
}
```
When `registration` is `None`, `stopWith` only calls `context.stop(self)`
without closing the channel.
`postStop` (lines 406-429) also fails to close the channel because the
`isCommandFailed` condition is true, routing to the `notifyInterested()` branch
instead of the `cancelAndClose` branch.
### Impact
The `SocketChannel` file descriptor is never explicitly closed. It relies on
GC finalization (via `AbstractInterruptibleChannel`'s cleaner) to eventually
close, which is non-deterministic and can lead to file descriptor exhaustion
under high connection-failure rates.
### Existing test coverage gap
`TcpIntegrationSpec.scala` (lines 187-201) tests the "reply with
CommandFailed when a connect socket option fails before connect" scenario but
does **not** verify that the underlying `SocketChannel` was closed.
### Suggested fix
In `TcpConnection.postStop`, add an explicit `channel.close()` call when
`registration` is `None` and the channel is still open:
```scala
override def postStop(): Unit = {
if (channel.isOpen) {
if (registration.isEmpty)
channel.close() // close unregistered channels directly
else
prepareAbort()
}
// ... rest of cleanup
}
```
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