Module structure
A module is a directory with files. Addon-operator searches for the modules directories in /modules or in the paths specified by the $MODULES_DIR variable. The module has the same name as the corresponding directory excluding the numeric prefix.
An example of the file structure of the module:
/modules/001-simple-module
├── crds
│ ├── doc-ru-projects.yaml
│ ├── doc-ru-projecttemplate.yaml
│ ├── projects.yaml
│ ├── projecttemplate.yaml
├── hooks
│ ├── module-hook-1.sh
│ ├── ...
│ └── module-hook-N.sh
├── openapi
│ ├── config-values.yaml
│ └── values.yaml
├── templates
│ ├── config-maps.yaml
│ ├── ...
│ └── daemon-set.yaml
├── enabled
├── README.md
├── .helmignore
├── Chart.yaml
└── values.yaml
crds— a directory with crd files.hooks— a directory with hooks.openapi— OpenAPI schemas for config values and for helm values.enabled— a script that gets the status of module (is it enabled or not). See the modules discovery process.Chart.yaml,.helmignore,templates— a Helm chart files.README.md— an optional file with the module description.values.yaml– default values for chart in a YAML format.
The name of this module is simple-module. values.yaml should contain a section simpleModule and a simpleModuleEnabled flag (see VALUES).
Notes on how Helm is used
values.yaml
Addon-operator does not use values.yaml as the only source of values for the chart. It generates a new file with a merged set of values (also mixing values from this file (see VALUES).
Chart.yaml
We recommend to define the “version” field in your Chart.yaml as “0.0.1” and use VCS to control versions. We also recommend to explicitly specify the “name” field even despite it is ignored: Addon-operator passes the module name to the Helm as a release name.
Releases deduplication
A module’s execution might be triggered by an event that does not change the values used by Helm templates (see modules discovery). Re-running Helm will lead to an “empty” release. To avoid this, Addon-operator runs a helm template command and compares a checksum of output with a saved checksum and starts the installation of a Helm chart only if there are changes.
Release auto-healing
The Addon-operator monitors resources defined by a Helm chart and triggers an update if something is deleted. This is useful for resources that Helm can’t update without deletion. It is worth noting, that resource deletion by hooks is smartly ignored to prevent needless updates.