Overview
Declarative hypothesis
HTTP probe
HTTP probe allows you to specify a URL that the experiment uses to determine the health or service availability (or other custom conditions) that is a part of the entry or exit criteria. The status code received is mapped against an expected status. It supports HTTP GET and POST methods.
Command probe
Command probe allows you to run Bash commands and match the output as a part of the entry or exit criteria. The intent behind this probe is to implement a non-standard and imperative way to express the hypothesis. For example, you can check for specific data within a database, parse the value out of a JSON blob that is dumped into a certain path, or check for the existence of a particular string in the service logs.
Kubernetes probe
With the proliferation of custom resources & operators, especially in the case of stateful applications, the steady-state is manifested as status parameters/flags within Kubernetes resources. K8s Probe addresses verification of the desired resource state by allowing users to define the Kubernetes GVR (group-version-resource) with appropriate filters (field selectors/label selectors). The experiment makes use of the Kubernetes Dynamic Client to achieve this. The probe supports following CRUD operations:
Prometheus probe
Prometheus probe allows users to run Prometheus queries and match the resulting output against specific conditions. The intent behind this probe is to allow users to define metrics-based SLOs in a declarative way and determine the experiment verdict based on its success. The probe runs the query on a Prometheus server defined by the endpoint, and checks whether the output satisfies the specified criteria. A PromQL query needs to be provided, whose outcome is then used for the probe validation.