Upgrade SIA

3rd-party/Sia-v1.1.1-windows-amd64/doc/Modules.md

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+Module Conventions
+==================
+
+Each module has a file/directory where they store persistent data (if
+necessary). When module.New is called, the module is responsible for creating
+and populating that directory. The logic for saving and loading data belongs in
+persist.go.
+
+Modules that depend on external information (such as the state of consensus)
+have an update.go to manage fetching and integrating the external information.
+If that information is coming from another module, a subscription should be
+used. Module subscription uses a ModuleSubscriber interface (which the
+subscriber must satisfy) and a ModuleSubscribe method (implemented by the
+parent module). As the parent module gets updates, it will call
+ReceiveModuleUpdate (the only method of the ModuleSubscriber interface) on all
+subscribers, taking care that each subscriber always receives the updates in
+the correct order. This method of subscription is chosen to keep information
+flow simple and synchronized - a child module should never have information
+that the parent module does not (it just causes problems).
+
+For testing, it is often important to know that an update has propagated to all
+modules. Any module that subscribes to another must also implement a
+ModuleNotify function in subscriptions.go. ModuleNotify returns a channel down
+which a struct{} will be sent every time that module receives an update from a
+parent module. To keep things simple, a module should not subscribe to the
+parent of another module that it is subscribed to. For example, the transaction
+pool is subscribed to the consensus set. Therefore, no module should subscribe
+to both the transaction pool and the consensus set. All consensus set updates
+should be received through the transaction pool. This helps with
+synchronization and ensures that no child module ever has information that the
+parent module has not yet received (desynchronization).
+
+#### Module Update Flow
+
+consensus -> (host, hostdb, renter, (transaction pool -> miner, wallet))