Better handle client connectivity state. #510
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Motivation: Pull grpc#506 highlighted some issues with client reconnectivity, namely a race between an automatic reconnection and the client closing the connection. In this case the delegate would report changes of state after the terminal shutdown state. Modifications: - State changes are now thread safe. - Record when a user initiates shutdown, ignore state changes beyond this point and close any channels created after this point. Result: More correct channel reconnectivity.
MrMage
approved these changes
Jul 11, 2019
| /// - `makeBootstrap(configuration:)`, and | ||
| /// - `verifyTLS(channel:)`. | ||
| /// - Parameter channel: The channel that was set. | ||
| private func didSetChannel(to channel: EventLoopFuture<Channel>) { |
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Why does this logic need to be split into will and did set?
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willSet is preparing the channel so that it can be used, didSet is advertising that self.channel may be used (or not in the case of shutdown).
If we had the current didSet logic in willSet then we potentially have race problems when e.g. waiting on .ready (since it would be triggered before actually assigning the new value). If the willSet logic was in didSet then it would be possible to call self.channel and hit an error (closing the channel) before the reconnect callback was registered.
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Motivation:
Pull #506 highlighted some issues with client reconnectivity, namely
a race between an automatic reconnection and the client closing the
connection. In this case the delegate would report changes of state
after the terminal shutdown state.
Modifications:
this point and close any channels created after this point.
Result:
More correct channel reconnectivity.