Extension Registration

Overview

Extensions needs to be registered with the agent. There are multiple ways to do that:

• Kubernetes Auto Registration (default behavior when using Kubernetes with our helm charts)

• Environment Variables

• Configuration Files (default behavior when using Linux packages)

• Agent API

Kubernetes Auto Registration

The agent is looking for services and pods with an annotation steadybit.com/extension-auto-registration. These annotations are already added to our extensions if you use our official helm charts.

Permissions

In order to automatically discover and register extensions present in the Kubernetes cluster, the agent needs access pod and service definitions via the Kubernetes API.

Appropriate permissions are already configured in the official helm charts by creating a (cluster) role granting get, list and watch on pods and services and a corresponding (cluster) role binding to a service account used for the agent pod. The used rules property is listed below.

rules:
  - apiGroups: [ "" ]
    resources:
      - "services"
      - "pods"
    verbs: [ "get", "list", "watch" ]

Kubernetes Auto Registration fine tuning

If you want to fine tune the auto registration, you can configure the mechanism to:

• include only extension pods matching a given label selector

• exclude extensions pod matching a given label selector

• include only extension from a specific namespace

using Helm Chart

agent:
  extensions:
    autoregistration:
      matchLabelsInclude:
        custom/extension-i-want-to-register: true
      matchLabelsExclude:
        app.kubernetes.io/name: extension-host
      namespace: my-namespace

using Environment Variables

STEADYBIT_AGENT_EXTENSIONS_AUTOREGISTRATION_MATCHLABELS_0_KEY=custom/extension-i-want-to-discover
STEADYBIT_AGENT_EXTENSIONS_AUTOREGISTRATION_MATCHLABELS_0_VALUE=true
STEADYBIT_AGENT_EXTENSIONS_AUTOREGISTRATION_MATCHLABELSEXCLUDE_0_KEY=app.kubernetes.io/name
STEADYBIT_AGENT_EXTENSIONS_AUTOREGISTRATION_MATCHLABELSEXCLUDE_0_VALUE=extension-host
STEADYBIT_AGENT_EXTENSIONS_AUTOREGISTRATION_NAMESPACE=my-namespace

Using Environment Variables

You can specify environment Variables via agent.env files or directly via the command line.

Please note that these environment variables are index-based (referred to as n) to register multiple extension instances.

Valid Types are:

• DISCOVERIES referring to a index response of a discovery.

• ACTIONS referring to a list of actions.

• EVENTS referring to a list of event listeners.

• ADVICE referring to a list of advices.

with specified type

Environment Variable (n refers to the index of the extension's instance) (type refers to the type of the extension's endpoint)	Required	Description
STEADYBIT_AGENT_type_EXTENSIONS_n_URL	yes	Fully-qualified URL of the endpoint, e.g., http://my-extension.steadybit-extension.svc.cluster.local:8080/actions
STEADYBIT_AGENT_type_EXTENSIONS_n_METHOD		Optional HTTP method to use. Default: GET
STEADYBIT_AGENT_type_EXTENSIONS_n_BASIC_USERNAME		Optional basic authentication username to use within HTTP requests.
STEADYBIT_AGENT_type_EXTENSIONS_n_BASIC_PASSWORD		Optional basic authentication password to use within HTTP requests.

Example: To register, e.g., two ACTION extensions, where the second one requires basic authentication, you use

• STEADYBIT_AGENT_ACTIONS_EXTENSIONS_0_URL,

• STEADYBIT_AGENT_ACTIONS_EXTENSIONS_1_URL,

• STEADYBIT_AGENT_ACTIONS_EXTENSIONS_1_BASIC_USERNAME and

• STEADYBIT_AGENT_ACTIONS_EXTENSIONS_1_BASIC_PASSWORD.

without specifying a type

You can also register extension without specifying the type, e.g., STEADYBIT_AGENT_EXTENSIONS_REGISTRATIONS_0_URL. In this case, the agent will try all known Types.

Environment Variable (n refers to the index of the extension's instance)	Required	Description
STEADYBIT_AGENT_EXTENSIONS_REGISTRATIONS_n_URL	yes	Fully-qualified URL of the endpoint, e.g., http://my-extension.steadybit-extension.svc.cluster.local:8080/actions
STEADYBIT_AGENT_EXTENSIONS_REGISTRATIONS_n_METHOD		Optional HTTP method to use. Default: GET
STEADYBIT_AGENT_EXTENSIONS_REGISTRATIONS_n_BASIC_USERNAME		Optional basic authentication username to use within HTTP requests.
STEADYBIT_AGENT_EXTENSIONS_REGISTRATIONS_n_BASIC_PASSWORD		Optional basic authentication password to use within HTTP requests.

Using Configuration Files

Linux packages installations are using this approach by default. The package installer of the extensions is writing configuration files to /etc/steadybit/extensions.d/extension-*.yaml which are read by the agent.

The content of each file is a YAML document with the following structure:

url: http://123.45.67.890:8085
types:
  - ACTION
  - DISCOVERY

Using the Agent API

You can also register extensions via the Agent API.

Extension registrations are persisted using the configured persistence provider. With each agent restart, the agent will re-register these manual extensions registrations.

You can find detailed information about the agent API in the Agent API documentation.

Example:

POST http://localhost:42899/extensions

{
  "url": "http://123.45.67.890:8085",
  "types": [
    "ACTION",
    "DISCOVERY"
  ]
}

Verify registered extensions

To check which extensions are registered in the agent, you need to take a look at the agent's logs.

Example output:

Jan 16 07:50:49 steadybit-agent-0 steadybit-agent INFO Extension-registry change: ADD Extension{source='KubernetesExtensionRegistrator', httpEndpointRef=GET http://steadybit-agent-extension-jmeter.steadybit-agent.svc.cluster.local:8087}
Jan 16 07:50:49 steadybit-agent-0 steadybit-agent INFO Extension-registry change: ADD Extension{source='KubernetesExtensionRegistrator', httpEndpointRef=GET http://steadybit-extension-loadtest-9005.steadybit-agent.svc.cluster.local:9005}
Jan 16 07:50:49 steadybit-agent-0 steadybit-agent INFO Extension-registry change: ADD Extension{source='KubernetesExtensionRegistrator', httpEndpointRef=GET http://steadybit-agent-extension-gatling.steadybit-agent.svc.cluster.local:8087}
Jan 16 07:50:49 steadybit-agent-0 steadybit-agent INFO Extension-registry change: ADD Extension{source='KubernetesExtensionRegistrator', httpEndpointRef=GET http://steadybit-agent-extension-k6.steadybit-agent.svc.cluster.local:8087}