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Feature/automatic resubscribe #398

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merged 22 commits into from
Apr 18, 2020
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SgtSilvio
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@SgtSilvio SgtSilvio commented Apr 6, 2020

Motivation
Resolves #297 and resolves #288
This is a prerequisite for proper implementation of manual acknowledgement and message persistence.

Changes

  • Enable subscribe(Stream) and unsubscribe independent of connect (similar to publishes)
  • Automatic resubscribe when automatically reconnecting and no session is present
  • Flows are not expired when automatic reconnect is enabled (instead subscriptions are automatically restored)
  • Improved concurrency of MqttPublishFlowableAckLink, FlowableWithSingleObserveOn and FluxWithSinglePublishOn

@cla-bot cla-bot bot added the cla-signed label Apr 6, 2020
@SgtSilvio SgtSilvio self-assigned this Apr 6, 2020
@SgtSilvio SgtSilvio force-pushed the feature/automatic-resubscribe branch from e3d20ec to 09efec5 Compare April 6, 2020 10:17
@SgtSilvio SgtSilvio requested review from gitseti, a user, AcidSepp and RobinAtherton and removed request for AcidSepp April 8, 2020 09:15
@SgtSilvio SgtSilvio mentioned this pull request Apr 15, 2020
@SgtSilvio SgtSilvio removed the request for review from RobinAtherton April 16, 2020 14:21
… to publishes)

Subscription and global flows are not expired when reconnect is enabled
Removed Flowable/FluxWithSingleCombine which had concurrency issues
Restored Flowable/FluxWithSingleCombine and fixed concurrency issues
…s more consistent: MqttIncomingPublishFlow(s) and MqttSubscribedPublishFlow(s))
@SgtSilvio SgtSilvio force-pushed the feature/automatic-resubscribe branch from 7b7a86e to 828edad Compare April 17, 2020 09:21
@sauroter sauroter self-requested a review April 17, 2020 09:21
subscriptionIdentifiersAvailable = connectionConfig.areSubscriptionIdentifiersAvailable();

if (!hasSession) {
incomingPublishFlows.getSubscriptions().forEach((subscriptionIdentifier, subscriptions) -> {
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I think this bahavior should be configurable somehow.

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What should be configurable?
If you use automatic reconnect and the server lost the session between the connection loss and a successful reconnect, why would you not want to resubscribe?

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This is actually feedback from users who are confused by SessionExpiredExceptions when they use automatic reconnect.

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Use case: You are in extremely constrained networks and want to be very precise on which data you send and when you send it.

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The same is true for resending publishes.
Isn't automatic reconnect the wrong choice if you want to have control over everything?

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@sauroter sauroter Apr 17, 2020

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The same is true for resending publishes.

I did not know that. But I would argue that the same logic applies.

I feel like the connect is something else. As it is the basis for everything afterwards. And in the connect there are possibilities to influence the behavior.

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So would a config to disable automatic resubscribe be enough?

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Yeah for a start I think so.

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Added configuration option: Reconnector.resubscribeIfSessionExpired (default true)
Also added a similar option for republishing: Reconnector.republishIfSessionExpired (default false)

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The code looks good. The question about the configurability of the resubscribe must be resolved.

…ibedPublishFlowTree, reasons:

the first is tightly coupled to the MqttOutgoingQosHandler
the second is similar to a collection which is instantiated
@SgtSilvio SgtSilvio merged commit d7b38e9 into develop Apr 18, 2020
@SgtSilvio SgtSilvio deleted the feature/automatic-resubscribe branch April 18, 2020 21:17
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