Whenever autopilot updates its state it notifies Consul. That notification will then trigger Consul to extract out the ready server information. If the ready servers have changed, then an event will be published to notify any subscribers of the full set of ready servers.
All these ready server event things are contained within an autopilotevents package instead of the consul package to make importing them into the grpc related packages possible
Previously we had 1 EventPublisher per state.Store. When a state store was closed/abandoned such as during a consul snapshot restore, this had the behavior of force closing subscriptions for that topic and evicting event snapshots from the cache.
The intention of this commit is to keep all that behavior. To that end, the shared EventPublisher now supports the ability to refresh a topic. That will perform the force close + eviction. The FSM upon abandoning the previous state.Store will call RefreshTopic for all the topics with events generated by the state.Store.
Adds a new gRPC streaming endpoint (WatchRoots) that dataplane clients will
use to fetch the current list of active Connect CA roots and receive new
lists whenever the roots are rotated.
Makes Payload a type with FilterByKey so that Payloads can implement
filtering by key. With this approach we don't need to expose a Namespace
field on Event, and we don't need to invest micro formats or require a
bunch of code to be aware of exactly how the key field is encoded.
Move the subscription context to Next. context.Context should generally
never be stored in a struct because it makes that struct only valid
while the context is valid. This is rarely obvious from the caller.
Adds a forceClosed channel in place of the old context, and uses the new
context as a way for the caller to stop the Subscription blocking.
Remove some recursion out of bufferImte.Next. The caller is already looping so we can continue
in that loop instead of recursing. This ensures currentItem is updated immediately (which probably
does not matter in practice), and also removes the chance that we overflow the stack.
NextNoBlock and FollowAfter do not need to handle bufferItem.Err, the caller already
handles it.
Moves filter to a method to simplify Next, and more explicitly separate filtering from looping.
Also improve some godoc
Only unwrap itemBuffer.Err when necessary
EventPublisher was receiving TopicHandlers, which had a couple of
problems:
- ChangeProcessors were being grouped by Topic, but they completely
ignored the topic and were performed on every change
- ChangeProcessors required EventPublisher to be aware of database
changes
By moving ChangeProcesors out of EventPublisher, and having Publish
accept events instead of changes, EventPublisher no longer needs to
be aware of these things.
Handlers is now only SnapshotHandlers, which are still mapped by Topic.
Also allows us to remove the small 'db' package that had only two types.
They can now be unexported types in state.
The EventPublisher is the central hub of the PubSub system. It is toughly coupled with much of
stream. Some stream internals were exported exclusively for EventPublisher.
The two Subscribe cases (with or without index) were also awkwardly split between two packages. By
moving EventPublisher into stream they are now both in the same package (although still in different files).
