Multiple Operators and Selective Upgrades

It’s possible to setup multiple Camel K operators in a cluster to watch the same namespaces. It’s not possible to configure Camel K this way using OLM (Operator Hub), since OLM prevents two operators from watching the same namespaces, but it’s technically possible to achieve this setup manually.

A typical example is when you install two global operators in different namespaces (e.g. kamel install --global --olm=false -n camel-ns-1 and kamel install --global --olm=false -n camel-ns-2). In this situation, both operators will watch the same resources in the cluster, so that if a user creates an integration in any namespace, both operators will contend the integration and the reconciliation will most probably result in an error (actual behavior is undefined).

To avoid contention, it’s possible to specify for each operator an ID and then assign any custom resource (CR) to a specific operator using an annotation. The assigned operator will be responsible for the reconciliation of the annotated CR.

In detail, the Camel K operator supports the environment variable KAMEL_OPERATOR_ID. The value is an identifier that can be equal to any string (e.g. KAMEL_OPERATOR_ID=operator-1). Once the operator is assigned an ID, it will only reconcile Camel custom resources that are assigned to that ID (unannotated resources will be ignored as well).

To assign a resource to a specific operator, the user can annotate it with camel.apache.org/operator.id. For example:

kind: Integration
apiVersion: camel.apache.org/v1
metadata:
  annotations:
    camel.apache.org/operator.id: operator-1
# ...

The annotation can be put on any resource belonging to the "camel.apache.org" group.

When a resource creates additional resources in order to proceed with the reconciliation (for example an Integration may create an IntegrationKit, which in turn creates a Build resource), the annotation will be propagated to all resources created in the process, so they’ll be all reconciled by the same operator.

By using the camel.apache.org/operator.id annotation, it’s possible to move integrations between two or more operators running different versions of the Camel K platform, i.e. selectively upgrading or downgrading them.

Configuring Multiple Integration Platforms

Any running Camel K integration is associated to a shared IntegrationPlatform resource that contains general configuration options. The integration platform is located in the integration namespace (or also in the operator namespace, in case of global installation) and typically only one ("primary", see later) integration platform is allowed to obtain a "Ready" state in a namespace, while others get the "Duplicate" state (i.e. IntegrationPlatform resources are somewhat "singleton" in a namespace).

There’s a way to allow two or more integration platforms to get a "Ready" state in a namespace and for them to be used by integrations: platforms can be marked with the annotation camel.apache.org/secondary.platform=true. That annotation marks the platform as secondary so that it will never be used as default platform during the reconciliation of an integration, unless explicitly selected (any resource belonging to the "camel.apache.org" group can select a particular integration platform). Secondary platforms are also allowed to reach the "Ready" state without becoming "Duplicate".

To specify which integration platform should be used to reconcile a specific CR, the CR can be annotated like in the following example:

kind: Integration
apiVersion: camel.apache.org/v1
metadata:
  annotations:
    camel.apache.org/platform.id: my-platform-name
# ...

The value of the camel.apache.org/platform.id annotation must match the name of an IntegrationPlatform custom resource, in the annotated resource namespace or also in the operator namespace.

The selection of a secondary IntegrationPlatform enables new configuration scenarios, for example, sharing global configuration options for groups of integrations, or also providing per-operator specific configuration options e.g. when you install multiple global operators in the same namespace.

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