Helm Dependencies: Difference between revisions
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Note that simply declaring the dependency in Chart.yaml is not sufficient. The dependency needs to be physically downloaded and placed in the charts/ subdirectory with: | Note that simply declaring the dependency in Chart.yaml is not sufficient. The dependency needs to be physically downloaded and placed in the charts/ subdirectory with: | ||
[[Helm_dependency#Dependency_Update|helm dependency update]] | [[Helm_dependency#Dependency_Update|helm dependency update]] | ||
==Aliases== | |||
Each element of the "dependencies" list allows for an optional "alias" attribute. | |||
=Packaging and Dependencies= | =Packaging and Dependencies= | ||
Revision as of 01:18, 16 December 2019
External
Internal
Overview
Revised for Helm 3
To Deplete
How Helm Dependencies Work
Helm does not automatically handle transitive dependencies, in the same manner as Maven, for example, does: it is not possible to specify that chart "a" depends on chart "b", only specify the chart "b" "coordinates" (name, version and repository URL) and expect Helm to automatically pull "b" during the installation process. In this situation. Maven would contact the dependency's repository and pull the artifact. If that artifact had its own dependencies, specified by coordinates, Maven would recursively pull those as well, contacting as many repositories as necessary. This is known as what Maven friends refer to as "downloading the Internet".
Helm behaves differently. It expects instead a chart to embed all dependencies it needs, recursively. This decision was probably taken because the chart metadata is really small, especially when compressed. and the chart transitive dependency graphs are not large, so embedding the whole graph in an archive is feasible, which would not be in Maven's case. Indeed, for a situation where an "a" chart depends on a "b" chart, and the "b" chart depends on a "c" chart, the structure of the "a"'s chart archive is;
a
├── Chart.yaml
├── charts
│ └── b
│ ├── Chart.yaml
│ ├── charts
│ │ └── c
│ │ ├── Chart.yaml
│ │ ├── templates
│ │ │ └── pod.yaml
│ │ └── values.yaml
│ ├── templates
│ │ └── pod.yaml
│ └── values.yaml
├── templates
│ └── pod.yaml
└── values.yaml
The enforcement of presence of dependencies happens when the chart is packaged with helm package command. If a chart is packaged manually, and its dependencies are omitted while building the chart archive, the chart archive cannot be installed. An attempt to install a chart archive that does not embed dependencies produces:
Error: found in Chart.yaml, but missing in charts/ directory: some-dependency-chart
For more details on how to package a chart with its dependencies, see:
Subcharts
The charts stored in the "charts/" subdirectory are also known as "subcharts".
Dependency Declaration
Dependencies are declared in Chart.yaml 'dependencies' section.
...
dependencies:
- name: # The name of the dependency
version: # The version of the dependency
repository: # Repository URL
...
Example:
...
# 'a' Chart.yaml
dependencies:
- name: b
version: 1.0.0
repository: http://helm-example.com/charts
...
Note that simply declaring the dependency in Chart.yaml is not sufficient. The dependency needs to be physically downloaded and placed in the charts/ subdirectory with:
helm dependency update
Aliases
Each element of the "dependencies" list allows for an optional "alias" attribute.
Packaging and Dependencies
Dependencies and Values
Dependency configuration values should be specified in the top chart values.yaml, and should be prefixed with the dependency name. It is recommended to only override values in the top level chart, and not in any subchart.
TODO:
- Example