Understanding OpenShift's Operator Lifecycle Manager (OLM) 

OpenShift's Operator Lifecycle Manager (OLM) is a powerful tool for managing Kubernetes Operators. It streamlines the deployment, updates, and overall lifecycle of these essential applications. This guide will delve into the core OLM components and their interactions, especially when utilizing Flat File Index (FBC) images for operator deployment.

Let's start by visualizing the end-to-end flow:

                          ┌─────────────────────────────┐
                          │   Flat File Index Image     │
                          │   (FBC / OCI catalog)       │
                          └────────────┬────────────────┘
                                       │
                                       ▼
                          ┌─────────────────────────────┐
                          │        CatalogSource        │
                          │ - Refers to FBC index       │
                          │ - Lists available packages  │
                          └────────────┬────────────────┘
                                       │
                                       ▼
                          ┌─────────────────────────────┐
                          │       Subscription          │
                          │ - Requests package install  │
                          │ - Points to channel/version │
                          └────────────┬────────────────┘
                                       │
                                       ▼
                          ┌─────────────────────────────┐
                          │        InstallPlan          │
                          │ - Plan to install CRDs,     │
                          │   CSVs, roles, deploys etc. │
                          └────────────┬────────────────┘
                                       │
                                       ▼
                          ┌─────────────────────────────┐
                          │   ClusterServiceVersion     │
                          │ (CSV)                       │
                          │ - Contains Operator spec    │
                          │ - CRDs, RBAC, version info  │
                          └────────────┬────────────────┘
                                       │
                                       ▼
                          ┌─────────────────────────────┐
                          │   Operator Pod Deployment   │
                          │ - From CSV spec             │
                          └────────────┬────────────────┘
                                       │
                                       ▼
                          ┌─────────────────────────────┐
                          │     CustomResourceDefinition│
                          │ (CRD)                        │
                          │ - Declares new API types     │
                          └────────────┬────────────────┘
                                       │
                                       ▼
                          ┌─────────────────────────────┐
                          │     CustomResource (CR)     │
                          │ - Created by user           │
                          │ - Triggers reconcile loop   │
                          └────────────┬────────────────┘
                                       ▼
                          ┌─────────────────────────────┐
                          │  Operator Reconcile Logic   │
                          │ - Reads CR and deploys      │
                          │   workloads/services/etc.   │
                          └─────────────────────────────┘

What's Managed by OLM?

Understanding what OLM manages and what falls under your responsibility is crucial:

Diving Deeper: OLM Core Components in OpenShift

Let's break down each key OLM component:

1. CatalogSource

• Type: OLM Resource

• Purpose: Defines the source of available operators (via an index image or gRPC endpoint).

• Function: Points to an FBC index image or other registry location, listing all available Packages (operators).

• ✅ Managed by Cluster Admins

• 📦 Backed by FBC (File-Based Catalog) or sqlite index DB.

2. OperatorGroup

• Type: OLM Resource

• Purpose: Defines the set of namespaces an operator is scoped to watch.

• Function: Associates operator deployments with target namespaces, supporting single-namespace, multi-namespace, or all-namespace mode.

• 🟡 Created in each operator namespace 

3. Subscription

• Type: OLM Resource

• Purpose: Requests installation/upgrade of a specific operator from a CatalogSource.

• Function: Automatically tracks updates to the operator and points to a channel in a Package.

• 🔁 Triggers creation of InstallPlan.

4. InstallPlan

• Type: OLM Resource (auto-generated)

• Purpose: Execution plan to install CRDs, CSVs, Roles, and Deployments.

• Function: Lists every resource to be installed or updated and applies them in order.

• 🔎 This is your go-to for debugging install failures.

5. ClusterServiceVersion (CSV)

• Type: OLM Resource (from bundle)

• Purpose: Describes the installed operator, version, and its capabilities.

• Function: Specifies the deployment spec of the operator pod, Custom Resource Definitions (CRDs), permissions and RBAC, and versioning info. Used to track the operator's lifecycle.

• 📜 One CSV per operator version in a namespace.

6. CustomResourceDefinition (CRD)

• Type: Kubernetes Resource

• Purpose: Declares a new API (kind) that the operator will manage.

• Function: Defines schema and validation for the operator's CustomResource (CR). Comes from the bundle/CSV during install.

• 🛠 Not OLM-specific but handled by OLM during install.

7. CustomResource (CR)

• Type: Kubernetes Resource

• Purpose: Your actual configuration input to the operator.

• Function: Triggers the operator to perform work (e.g., install backend services). Managed by the operator runtime logic.

• ✏️ Created by you (user, script, or UI).

8. OLM Core Pods

These essential pods run in the openshift-operator-lifecycle-manager namespace:

You can inspect them via:

oc get pods -n openshift-operator-lifecycle-manager
oc logs -n openshift-operator-lifecycle-manager <pod-name>

What Happens When You oc apply these YAMLs?

• Apply CatalogSource: OLM sees a new catalog, pulls the index, and exposes operator packages.

• Apply OperatorGroup: Defines the scope in which operators can run and watch CRs.

• Apply Subscription: OLM creates an InstallPlan, chooses a CSV, and installs the operator.

• Operator pod starts: Based on the Deployment spec in the CSV.

• CRDs are installed: Your APIs become available.

• User creates a CustomResource: Triggers the operator to act on it and deploy components.

Summary Table of OLM Component Commands

Understanding these components and their interactions is crucial for anyone working with OpenShift Operators, enabling efficient deployment, management, and troubleshooting. The Flat File Index images simplify the cataloging process, making OLM even more robust for enterprise deployments.