appcat

AppCat

This repository has k8s tools to manage AppCat services.

Documentation: https://vshn.github.io/appcat

Architecture

.
├── apis
|   ├── appcat // API server related apis
|   ├── exoscale // exoscale apis
|   ├── v1 // common apis
|   ├── vshn // VSHN managed services apis
├── cmd // cobra command lines for each AppCat tool
|   ├── apiserver.go
|   ├── controller.go
|   ├── grpc.go
│   └── sliexporter.go
├── config // kubernetes resources
|   ├── apiserver
│   ├── controller
│   └── sliexporter // uses kustomize
├── crds // VSHN exposed resources from apis
├── docs
├── pkg // go code for each AppCat tool
|   ├── apiserver
|   ├── controller
|   ├── grpc
│   └── sliexporter
├── test // mocks, test cases, grps test client
├── Dockerfile
├── log.go
├── main.go
├── probes
├── README.md
└── tools.go

Generate Kubernetes code, XRDs with Go / KubeBuilder

In /apis there is code in Go to generate the XRDs (composites) as this is in OpenAPI. This code generates the OpenAPI scheme using Kubebuilder.

See following pages for learning how to do that:

• https://kubebuilder.io/reference/generating-crd.html
• https://kubebuilder.io/reference/markers.html

If you make changes to the auto generated code you'll need to run code generation. This can be done with make:

make generate

Building

See make help for a list of build targets.

• make build: Build binary for linux/amd64
• make build -e GOOS=darwin -e GOARCH=arm64: Build binary for macos/arm64
• make docker-build: Build Docker image for local environment

Local development environment

You can setup a [kind]-based local environment with all dependencies in kindev.

Controller

The AppCat Controller resolves certain issues that cannot be achieved with crossplane.

Capabilities

The controller manages and achieves the following:

Local Webhook debugging

This assumes that you've already applied the vshn golden test in component-appcat!

Also you might need to set the right host ip:

HOSTIP=$(docker inspect kindev-control-plane | jq '.[0].NetworkSettings.Networks.kind.Gateway') # On kind MacOS/Windows
HOSTIP=host.docker.internal # On Docker Desktop distributions
HOSTIP=host.lima.internal # On Lima backed Docker distributions
For Linux users: `ip -4 addr show dev docker0 | grep inet | awk -F' ' '{print $2}' | awk -F'/' '{print $1}'`

Then you can apply the webhook registration changes:

export KUBECONFIG=...
make webhook-debug -e webhook_service_name=$HOSTIP

Then run the controller with the correct certdir flag:

go run . controller --certdir .work/webhook

Creating a PostgreSQL or Redis instance will now go through the Webhook instance.

SLI Exporter

Metrics

The exporter exposes a histogram appcat_probes_seconds with five labels

• service, the service type that was probed (e.g. VSHNPostgreSQL)
• namespace, the namespace of the claim that was monitored
• name, the name of the claim that was monitored
• sla, the service level. Can either be besteffort or guaranteed
• high_available, whether this instance is high available (1 or more nodes)
• reason, if the probe was successful. Can either be success, fail-timeout, or fail-unkown

Adding a Prober

To add a prober for a new service, add a file in pkg/sliexporter/probes/ that adds another implementation of the Prober interface.

Adding an AppCat service

There should be a separate controller per AppCat Claim type. Add another controller for each service that should be probed in pkg/sliexporter/.

Adding SLA exceptions

If possible SLA exceptions should be implemented as a middleware for the Prober interface.

Crossplane Composition Functions with gRPC Server

The gRPC Server that manages crossplane composition functions. The functions are found in pkg/comp-functions/functions There package pkg/comp-functions/runtime contains a library with helper methods which helps with adding new functions.

Add a new function-io

The framework is designed to easily add new composition functions to any AppCat service. A function-io corresponds to one and only one composition thus multiple transformation go functions can be added to a function-io. For instance, in vshn-postgres-func there are multiple transformation go functions such as url or alerting.

To add a new function to PostgreSQL by VSHN:

• Create a new package under ./pkg/comp-functions/functions/ in case one does not exist for a composition.
• Implement a Transform() go function by using the helper functions from runtime/desired.go and runtime/observed.go.
• Add a new transform go function to the images variable in ./cmd/grpc.go.

Usage of gRPC server - local development + kind cluster

entrypoint to start working with gRPC server is to run:

go run main.go --log-level 1 functions --insecure

This will start the GRPC server listening on a TCP port. Afterward you can configure the composition to use this connection in the component:

# HOSTIP=$(docker inspect kindev-control-plane | jq '.[0].NetworkSettings.Networks.kind.Gateway') # On kind MacOS/Windows
        # HOSTIP=host.docker.internal # On Docker Desktop distributions
        # HOSTIP=host.lima.internal # On Lima backed Docker distributions
        # For Linux users: `ip -4 addr show dev docker0 | grep inet | awk -F' ' '{print $2}' | awk -F'/' '{print $1}'`
services:
  vshn:
    enabled: true
    externalDatabaseConnectionsEnabled: true
    emailAlerting:
      enabled: true
      smtpPassword: "whatever"
    postgres:
      grpcEndpoint: $HOSTIP:9547
      proxyFunction: true

Each service should have these params configured.

If you prefer to set the proxy endpoint directly in the composition, it's passed via the input.data.proxyEndpoint field.

Then install the function proxy in kind:

make install-proxy

It's also possible to trigger fake request to gRPC server via the crank renderer:

go run github.com/crossplane/crossplane/cmd/crank beta render xr.yaml composition.yaml functions.yaml -r

Crank will return a list of all the objects this specific request would have produced, including the result messages.

Please have a look at the hack/ folder for an example.