mirror of https://github.com/status-im/consul.git
36 lines
2.2 KiB
Markdown
36 lines
2.2 KiB
Markdown
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# Adding a new topic to streaming
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This document is a guide for adding a new streaming topic.
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1. Add the name of the topic to the [proto/pbsubscribe/subscribe.proto Topic enum][1].
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Run `make proto` to generate the Go code from the protobuf.
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2. Add a `FromChanges` function to the list of change functions in
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[agent/consul/state.processDBChanges][2]. The `FromChanges` function should examine the
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list of `Changes` and return a list of events that subscriptions would need to update
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their view.
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3. Add a snapshot function to [agent/consul/state.newSnapshotHandlers][3]. The snapshot
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function should produce a set of events to create the initial state of the view.
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Generally these are all "create" events.
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4. Add a new `Payload` type, similar to [agent/consul/state.EventPayloadCheckServiceNode][6].
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This type will be used in the `Payload` field of the event.
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5. Create the protobuf for the payload, and add the `Payload` type to the `oneof` in
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[proto/pbsubscrube/subscribe.proto Event.Payload][7]. This may require creating other
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protobuf types as well, to encode anything in the payload. Run `make proto` to generate
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the Go code from the protobuf.
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6. Add another case to [agent/rpc/subscribe.setPayload][8] to convert from the Payload
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type in `state`, to the protobuf type. This may require either writing or generating a
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function to convert between the types.
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7. Add a new cache-type that uses [agent/submatview.Materializer][4] similar to
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[agent/cache-types/streaming_health_services.go][5].
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[1]: https://github.com/hashicorp/consul/blob/v1.9.4/proto/pbsubscribe/subscribe.proto#L37-L45
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[2]: https://github.com/hashicorp/consul/blob/v1.9.4/agent/consul/state/memdb.go#L188-L192
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[3]: https://github.com/hashicorp/consul/blob/v1.9.4/agent/consul/state/memdb.go#L205-L209
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[4]: https://github.com/hashicorp/consul/blob/v1.9.4/agent/submatview/materializer.go#L76
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[5]: https://github.com/hashicorp/consul/blob/v1.9.4/agent/cache-types/streaming_health_services.go
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[6]: https://github.com/hashicorp/consul/blob/v1.9.4/agent/consul/state/catalog_events.go#L12-L46
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[7]: https://github.com/hashicorp/consul/blob/v1.9.4/proto/pbsubscribe/subscribe.proto#L95-L117
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[8]: https://github.com/hashicorp/consul/blob/v1.9.4/agent/rpc/subscribe/subscribe.go#L161-L168
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