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129 lines
5.4 KiB
Markdown
129 lines
5.4 KiB
Markdown
## Data Plane Aggregator
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The data plane aggregator is a reverse proxy similar to `kube-aggregator` that sits first in the request path. It is responsible for reverse proxying any registered data plane (anything that isn't CRUD + List + Watch) routes to the appropriate app handlers. Anything that does not match the registered data planeroutes will be delegated to the next apiserver in the handler chain (e.g. `kube-aggregator`). Currently the aggregator uses the Grafana plugin framework to register and proxy requests to Grafana plugins. The benefit of this approach is that it allows apps to be built, packaged, published, and deployed using the existing Grafana plugin framework.
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### Architecture
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The data plane aggregator is built on top of the Kubernetes API server framework. It introduces a new `DataPlaneService` Custom Resource Definition (CRD) to dynamically register and proxy requests to Grafana plugins.
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The main components are:
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* **GrafanaAggregator**: The main server component, located in `pkg/aggregator/apiserver/apiserver.go`. It's responsible for:
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* Creating a generic API server.
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* Registering the `DataPlaneService` resource.
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* Running the `DataPlaneServiceRegistrationController`.
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* **DataPlaneServiceRegistrationController**: This controller, located in `pkg/aggregator/apiserver/dataplaneservice_controller.go`, is responsible for:
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* Watching for `add`, `update`, and `delete` events on `DataPlaneService` resources.
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* Passing the `DataPlaneService` to the `PluginHandler` to add, update, or remove the corresponding proxy handlers.
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* **PluginHandler**: This handler, located in `pkg/aggregator/apiserver/plugin/handler.go`, is responsible for:
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* Translating between the HTTP request/response and Grafana plugin request/response.
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* Adding and removing HTTP handlers to proxy requests to plugins based on the registered `DataPlaneService` resources.
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* **DataPlaneService**: Defined in `pkg/aggregator/apis/aggregation/v0alpha1/types.go`, this represents a service provided by a Grafana plugin.
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The following diagram illustrates the request flow:
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```mermaid
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sequenceDiagram
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autonumber
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participant plugin as disk
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participant exe as plugin<br>binaries
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participant wrap as apiserver
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participant agg as kube-aggregator
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participant data as dataplane-aggregator
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participant storage as Unified<br>Storage
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Note over plugin,storage: Registration
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wrap->>plugin: Load Scope app manifest
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wrap->>agg: Create Scope APIService
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wrap->>plugin: Load SLO app manifest
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wrap->>agg: Create SLO APIService
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wrap->>plugin: Load Dashboard app manifest
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wrap->>agg: Create Dashboard APIService
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wrap->>data: Create Dashboard DataPlaneService
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Note over plugin,storage: Storage Access
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data->>storage: DataPlaneServices
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agg->>storage: APIServices
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wrap->>storage: Custom resources
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Note over plugin,storage: Create, Update, or Delete Hooks
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data->>agg: Local delegation to kube-aggregator
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agg->>wrap: HTTP reverse proxy incoming request
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wrap->>exe: gRPC admission mutation hook
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wrap->>exe: gRPC admission validation hook
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Note over plugin,storage: Get, List, or Watch Hooks
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data->>agg: Local delegation to kube-aggregator
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agg->>wrap: HTTP reverse proxy incoming request
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wrap->>exe: gRPC conversion hook
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Note over plugin,storage: Subresource & Custom Routes
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data->>exe: gRPC plugin resource calls
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data->>exe: gRPC plugin query data
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data->>exe: gRPC plugin stream
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data->>exe: gRPC plugin health
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data->>exe: gRPC plugin metrics
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Note over plugin,storage: Async (controllers)
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exe->>data: Watch
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data->>agg: Local delegation to kube-aggregator
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agg->>wrap: HTTP reverse proxy incoming request
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wrap->>storage: Watch
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```
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## DataPlaneService
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A `DataPlaneService` is a non-namespaced resource that represents a service exposed by a Grafana plugin. Here is an example:
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```yaml
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apiVersion: aggregation.grafana.app/v0alpha1
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kind: DataPlaneService
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metadata:
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name: <plugin-id>
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spec:
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pluginID: <plugin-id>
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pluginType: <plugin-type> # app or datasource
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group: <api-group>
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version: <api-version>
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services:
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- type: <service-type> # admission, conversion, query, stream, route, datasource-proxy
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method: <http-method>
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path: <url-path>
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```
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### Query Example
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1. `custom.ini` changes:
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```ini
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[feature_toggles]
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kubernetesAggregator = true
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dataplaneAggregator = true
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grafanaAPIServerEnsureKubectlAccess = true
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```
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2. start grafana:
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```bash
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make run
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```
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3. enable aggregation for prometheus data source:
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```bash
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export KUBECONFIG=./data/grafana-apiserver/grafana.kubeconfig
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kubectl apply -f pkg/aggregator/examples/datasource.yml --validate=false
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dataplaneservice.aggregation.grafana.app/v0alpha1.prometheus.grafana.app created
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```
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4. edit `pkg/aggregator/examples/datasource-query.json` and update the datasource UID to match the UID of a prometheus data source.
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5. execute query (replace `example` with the UID of a prometheus data source):
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```bash
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curl 'http://admin:admin@localhost:3000/apis/prometheus.grafana.app/v0alpha1/namespaces/default/connections/example/query' -X POST -d '@pkg/aggregator/examples/datasource-query.json'
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```
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### Research/PoC's
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* [PoC Alternate HTTP backend](https://github.com/grafana/grafana/pull/100697)
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* [PoC Plugin SDK <--> App SDK Adapter](https://github.com/grafana/grafana-app-sdk/pull/493) |