Extension Discovery

Overview

Extensions needs to be discovered by the agent. There are two ways to do that:

Kubernetes Auto Discovery

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

Kuberenetes Auto Discovery fine tuning

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

• include only extensions pods matching a given label selector

• exclude extensions pods matching a given label selector

using Helm Chart

agent:
  extensions:
    autodiscovery:
      matchLabelsInclude:
        custom/extension-i-want-to-discover: true
      matchLabelsExclude:
        app.kubernetes.io/name: extension-host

using Environment Variables

STEADYBIT_AGENT_EXTENSIONS_AUTODISCOVERY_MATCHLABELS_0_KEY=custom/extension-i-want-to-discover STEADYBIT_AGENT_EXTENSIONS_AUTODISCOVERY_MATCHLABELS_0_VALUE=true STEADYBIT_AGENT_EXTENSIONS_AUTODISCOVERY_MATCHLABELSEXCLUDE_0_KEY=app.kubernetes.io/name STEADYBIT_AGENT_EXTENSIONS_AUTODISCOVERY_MATCHLABELSEXCLUDE_0_VALUE=extension-host

Manual Extension Registration

If you can't use the Kubernetes Auto Discovery, you need to register the extension manually.

Using ENV Variables

You can specify ENV 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 replacement for type 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.

• ADVICES referring to a list of advices.

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.

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:

2024-09-16T14:02:35.687+02:00  INFO 22305 --- [steadybit-agent] [           main] c.s.e.d.s.ExtensionDiscoveryService      : Extension-discovery change: ADD DiscoveredExtension[source=PropertyBasedExtensionDiscovery, type=ACTION, httpEndpointRef=GET http://xxx.yy:8082]
2024-09-16T14:02:35.688+02:00  INFO 22305 --- [steadybit-agent] [           main] c.s.e.d.s.ExtensionDiscoveryService      : Extension-discovery change: ADD DiscoveredExtension[source=PropertyBasedExtensionDiscovery, type=ACTION, httpEndpointRef=GET http://xxx.yy:8084]
2024-09-16T14:02:35.688+02:00  INFO 22305 --- [steadybit-agent] [           main] c.s.e.d.s.ExtensionDiscoveryService      : Extension-discovery change: ADD DiscoveredExtension[source=PropertyBasedExtensionDiscovery, type=DISCOVERY, httpEndpointRef=GET http://xxx.yy:8091]
2024-09-16T14:02:35.688+02:00  INFO 22305 --- [steadybit-agent] [           main] c.s.e.d.s.ExtensionDiscoveryService      : Extension-discovery change: ADD DiscoveredExtension[source=PropertyBasedExtensionDiscovery, type=EVENT, httpEndpointRef=GET http://xxx.yy:8088]
2024-09-16T14:02:35.688+02:00  INFO 22305 --- [steadybit-agent] [           main] c.s.e.d.s.ExtensionDiscoveryService      : Extension-discovery change: ADD DiscoveredExtension[source=PropertyBasedExtensionDiscovery, type=EVENT, httpEndpointRef=GET http://xxx.yy:8087]
2024-09-16T14:02:35.688+02:00  INFO 22305 --- [steadybit-agent] [           main] c.s.e.d.s.ExtensionDiscoveryService      : Extension-discovery change: ADD DiscoveredExtension[source=PropertyBasedExtensionDiscovery, type=ADVICE, httpEndpointRef=GET http://xxx.yy:8089]
2024-09-16T14:02:35.688+02:00  INFO 22305 --- [steadybit-agent] [           main] c.s.e.d.s.ExtensionDiscoveryService      : Extension-discovery change: ADD DiscoveredExtension[source=PropertyBasedExtensionDiscovery, type=DISCOVERY, httpEndpointRef=GET http://xxx.yy:8090]