Customization point: Application Charts

Epinio uses Application charts as templates for the structure of deployed applications, i.e. of the kubernetes resources used to run an application image.

An installation of Epinio provides a single standard application chart.

If custom application charts adapted to the local environment are desired or needed please follow the instructions on How to create custom application Helm charts and How to use custom application Helm charts.

Application charts are expected to create the following resources:

• A Deployment, StatefulSet, or similar main controller, specifying the Pod and its containers running the application image.

• A Service to route web requests to the application.

• An Ingress per specified route to front the Service.

note

Up to version 1 Epinio allowed only Deployment resources as the main controller of applications.

tip

Read the contents of the standard application chart.

Further Expectations

Application Charts are expected to heed the following contraints to enable their use by Epinio:

1. It has to support all of the configuration values described in section Configuration below.

2. Pod resources have to have a number of annotations and labels for Epinio to locate and use them, as described in section Pods below.

note

While a custom chart is free to support more configuration values Epinio will have no knowledge of them, and will not use them.

Configuration

All configuration fields below are provided in the epinio hierarchy:

Name	Kind	Meaning
appName	string	The application's name
configurations	sequence (string)	The names of the configurations to import into the application
env	sequence (assignment)	The application's environment variables and their values
imageURL	string	A reference to the app image in Epinio's registry
ingress	string	The ingress class name to use, if any
replicaCount	integer	The desired number of instances (pods) to deploy
routes	sequence (route)	The routes (= domain+path+id) the app has to be reachable at
stageID	string	Id of the stage run which generated the app image
start	integer	Optional. The time of deployment, in nanoseconds
tlsIssuer	string	The name of the cert issuer to use for route certs
username	string	The name of the user deploying the application
userConfig	map (string -> any)	The names and values of all chart values set by the user

Routes are maps composed of four keys:

Name	Kind	Meaning
domain	string	The domain of the route
id	string	A unique id to name route Ingress and Certificate resources with
path	string	The sub-path of the route, if any
secret	string	Optional. Name of a Secret to directly use in securing the Ingress

note

The Routing Secrets reference explains more about the secrets field.

Environment assigment are maps composed of two keys:

Name	Kind	Meaning
name	string	The name of the variable
value	string	The value of the variable

The user configuration map is keyed by the names of chart values set by the user, referencing the set values.

note

Please read How to create custom application Helm charts for more information about defining user-settable chart values when creating a custom app chart.

Please read How to use custom application Helm charts for more information about using user-settable chart values when deploying an application.

Pods

Epinio adds the following annotations to the Pods:

Annotation	Meaning
app.kubernetes.io/name	The application's name.
epinio.io/start	The time of deployment, in nanoseconds, if provided by Epinio

Epinio adds the following labels to the Pods:

Label	Meaning
app.kubernetes.io/component	Fixed: application
app.kubernetes.io/created-by	The name of the user deploying the application
app.kubernetes.io/managed-by	Fixed: epinio
app.kubernetes.io/name	The application's name.
app.kubernetes.io/part-of	The application's namespace
epinio.io/app-container	The name of the main Pod container, running the app image
epinio.io/stage-id	Id of the stage run which generated the app image
helm.sh/chart	Chart name and version used to deploy the application

tip

Read the contents of the standard application chart.

Related

• Routing Secrets