2a9273142a
The previous code was trying to do too much with local dataflow. This refactoring splits (stateful) relay upstream subscriptions out into actors of their own. Previously, dataflow variables were used to hold a single upstream hub and a single upstream canonical topic URL. This causes problems when things change rapidly: an unsubscription or subscription might be in flight, and there was no way to tell what the resulting state of the remote topic as a whole should be if the fields had changed between the start and finish of an in flight action. The new design follows from the observation that an individual subscription to an upstream hub is a stateful entity: it deserves promotion to a full actor. There is now an actor for the remote topic, and one for each established upstream subscription. Upstream subscriptions are created in response to demand expressed by the remote topic actor; to switch, all it needs to do is update its demand, and new subscriptions will spring into being while surplus subscriptions gracefully terminate. Also, this commit fixes a bug where upstream subscriptions were being made to the requested-topic rather than to the upstream-topic. Consequently, self-subscriptions (with multiple `http-listener` aliases) work now without infinite mail loops. There is still an issue that blocking actions in on-stop clauses don't run to completion; that is being dealt with separately, as part of a reexamination of facet-terminating events more generally. |
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| .. | ||
| htdocs | ||
| hub | ||
| log | ||
| private | ||
| templates | ||
| config.rkt | ||
| defaults.rktd | ||
| hub.rkt | ||
| info.rkt | ||
| poke.rkt | ||
| protocol.rkt | ||
| run | ||
| template.rkt | ||