application-connector/

Application Connector

This is the repository for the Application Connector. See this directory for more documentation for this component.

Prerequisites

The Application Connector requires Go 1.8 or higher.

Installation

To install the Application Connector components, follow these steps:

1. git clone git@github.com/kyma-project/kyma/components/application-connector
2. cd application-connector
3. CGO_ENABLED=0 go build ./cmd/metadata

Usage

This section explains how to use the Application Connector.

Start the Metadata service

To start the Metadata Service, run this command:

./metadata

The Metadata Service has the following parameters:

• proxyPort - This port acts as a proxy for the calls from services and lambdas to an external solution. The default port is 8080.
• externalAPIPort - This port exposes the Metadata API to an external solution. The default port is 8081.
• eventsTargetURL - A URL to which you proxy the incoming events. The default URL is http://localhost:9000.
• appName - The name of the Metadata Service instance. The default is metadata.
• namespace - Namespace where Metadata Service is deployed. The default Namespace is kyma-system.
• requestTimeout - A time-out for requests sent through the Metadata Service. It is provided in seconds. The default time-out is 1.
• skipVerify - A flag for skipping the verification of certificates for the proxy targets. The default value is false.
• requestLogging - A flag for logging incoming requests. The default value is false.

Sample calls

• Create a new service

curl -X POST http://localhost:32000/ec-default/v1/metadata/services \
  -d '{"name": "Some EC",
  "provider": "kyma",
  "description": "This is some EC!",
  "api": {
    "targetUrl": "https://ec.com/rest/v2/",
    "credentials": {
      "oauth": {
        "url": "https://ec.com/authorizationserver/oauth/token",
        "clientId": "CLIENT_ID",
        "clientSecret": "CLIENT_SECRET"
      }
    },
    "spec": {
      "apispec": "This is API spec..."
    }
  },
  "events": {
    "spec": {
      "eventsspec": "This is Events Spec..."
    }
  },
  "documentation": {
    "displayName": "Documentation",
    "description": "Description",
    "type": "sometype",
    "tags": ["tag1", "tag2"],
    "docs": [
        {
        "title": "Documentation title...",
        "type": "type",
        "source": "source"
        }
    ]
  }
}'

• Fetch all services

curl http://localhost:32000/ec-default/v1/metadata/services

Development

This section explains the development process.

Rapid development with Telepresence

The Application Connector stores its state in the Kubernetes Custom Resource, therefore it's dependent on Kubernetes. You cannot mock the dependency. You cannot develop locally. Manual deployment on every change is a mundane task.

You can, however, leverage Telepresence. This works by replacing a container in a specified Pod, opening up a new local shell or a pre-configured bash, and proxying the network traffic from the local shell through the Pod.

Although you are on your local machine, you can make calls such as curl http://....svc.cluster.local:8081/v1/metadata/services. When you run a server in this shell, other Kubernetes services can access it.

1. Install telepresence.
2. Run Kyma or use the cluster. In the case of Kyma, point your local kubectl to Kyma in Docker.
3. Check the Deployment name to swap and run: telepresence --namespace <NAMESPACE> --swap-deployment <DEPLOYMENT_NAME>:<CONTAINER_NAME> --run-shell

telepresence --namespace kyma-system --swap-deployment metadata:metadata --run-shell

1. Every Kubernetes Pod has /var/run/secrets mounted. The Kubernetes client uses it in the Application Connector services. It is hardcoded. By default, telepresence copies this directory. It stores the directory path in $TELEPRESENCE_ROOT, under telepresence shell. It unwinds to /tmp/tmp.... You need to move it to /var/run/secrets, where the service expects it. Create a symlink:

sudo ln -s $TELEPRESENCE_ROOT/var/run/secrets /var/run/secrets

1. Run CGO_ENABLED=0 go build ./cmd/metadata to build the Metadata Service and give all Kubernetes services that call the Metadata Service access to this process. The process runs locally on your machine. Use the same command to run different Application Connector services like Proxy or Events.

You can also run another shell to make calls to this service. To run this shell, swap the Remote Environment Broker Deployment, because Istio sidecar is already injected into this Deployment:

telepresence --namespace kyma-system --swap-deployment kyma-core-remote-environment-broker:reb --run-shell

Generate mocks

To generate a mock, follow these steps:

1. Go to the directory where the interface is located.
2. Run this command:

mockery -name=Sender

Tests

This section outlines the testing details.

Unit tests

To run the unit tests, use the following command:

go test ./...

Generate Kubernetes clients for custom resources

1. Create a directory structure for each client, similar to the one in pkg/apis. For example, when generating a client for EgressRule in Istio, the directory structure looks like this: pkg/apis/istio/v1alpha2.
2. After creating the directories, define the following files:
   • doc.go
   • register.go
   • types.go - define the custom structs that reflect the fields of the custom resource.

See an example in pkg/apis/istio/v1alpha2.

1. Go to the project root directory and run ./hack/update-codegen.sh. The script generates a new client in pkg/apis/client/clientset.

Contract between the Application Connector and the UI API Facade

The UI API Facade must check the status of the Application Connector services instances that represent the Remote Environment. In the current solution, the UI API Facade iterates through services to find those which match the criteria, and then uses the health endpoint to determine the status. The UI API Facade has the following obligatory requirements:

• The Kubernetes service for each Application Connector service uses the remoteEnvironment key, with the value as the name of the Remote Environment.
• The Kubernetes service for each Application Connector service contains one port with the ext-api-port name. The system uses this port for the status check.
• Find the Kubernetes Application Connector service service in the kyma-integration Namespace. You can change its location in the ui-api-layer chart configuration.
• The /v1/health endpoint returns a status of HTTP 200. Any other status code indicates the service is not healthy.

Contribution

To learn how you can contribute to this project, see the Contributing document.