Init Containers Trait

The InitContainersTrait trait can be used to configure init containers or sidecar containers.

This trait is available in the following profiles: Kubernetes, Knative, OpenShift.

Configuration

Trait properties can be specified when running any integration with the CLI:

$ kamel run --trait init-containers.[key]=[value] --trait init-containers.[key2]=[value2] integration.yaml

The following configuration options are available:

Property Type Description

init-containers.enabled

bool

Can be used to enable or disable a trait. All traits share this common property.

init-containers.init-tasks

[]string

A list of init tasks to be executed with format <name>;<container-image>;<container-command>.

init-containers.sidecar-tasks

[]string

A list of sidecar tasks to be executed with format <name>;<container-image>;<container-command>.

An example init container

Create an Integration which read some value initialized by an init container. The following route takes care to read a file which is expected to be initialized by another process.

route.yaml
- route:
    from:
      # Read a file that should have been initialized
      # by the initContainer
      uri: file:/tmp
      parameters:
        include: ^(init).*
      steps:
        - log:
            message: "${body}"

The route is agnostic how this file is generated.

When creating the Integration, then, it should include an init container taking care to initialize such file, for example:

kamel run route.yaml -t mount.empty-dirs=common:/tmp -t init-containers.init-tasks="init;alpine;/bin/sh -c \"echo hello >> /tmp/init\""

As the file is shared between the containers you will need to provide a shared volume (an EmtpyDir in this case).

An example sidecar container

Create an Integration which generate some values on a folder shared by the main Integration. This process is done by a sidecar container. The route takes care to read the files without knowing the process generating.

route.yaml
- route:
    from:
      # Read a file that should have been initialized
      # by the initContainer
      uri: file:/tmp
      parameters:
        include: ^(sidecar).*
      steps:
        - log:
            message: "${body}"

The route is agnostic how this file is generated.

When creating the Integration, then, it should include the sidecar container:

kamel run route.yaml -t mount.empty-dirs=common:/tmp -t init-containers.init-tasks="init;alpine;/bin/sh -c \"echo hello >> /tmp/init\""

kamel run route.yaml -t mount.empty-dirs=common:/tmp -t init-containers.sidecar-tasks="sidecar;alpine;/bin/sh -c \"for i in $(seq 1 10); do echo helloSidecar$i > /tmp/sidecar_$i.txt; sleep 1; done\""

As the file is shared between the containers you will need to provide a shared volume (an EmtpyDir in this case). Mind that the sidecar container can be any other process embedded into a docker container: in this simple case we’re creating a simple script to generate some content.

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