53 lines
2.7 KiB
Markdown
53 lines
2.7 KiB
Markdown
# How it works
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This document describes a high level overview how **Jenkins Operator** works.
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1. [Architecture and design](#architecture-and-design)
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2. [Operator State](#operator-state)
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3. [System Jenkins Jobs](#system-jenkins-jobs)
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3. [Jenkins Docker Images](#jenkins-docker-images)
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## Architecture and design
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The **Jenkins Operator** design incorporates the following concepts:
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- watches any changes of manifests and maintain the desired state according to deployed custom resource manifest
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- implements the main reconciliation loop which consists of two smaller reconciliation loops - base and user
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**Base** reconciliation loop takes care of reconciling base Jenkins configuration, which consists of:
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- Ensure Manifests - monitors any changes in manifests
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- Ensure Jenkins Pod - creates and verifies status of Jenkins master Pod
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- Ensure Jenkins Configuration - configures Jenkins instance including hardening, initial configuration for plugins, etc.
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- Ensure Jenkins API token - generates Jenkins API token and initialized Jenkins client
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**User** reconciliation loop takes care of reconciling user provided configuration, which consists of:
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- Ensure Restore Job - creates Restore job and ensures that restore has been successfully performed
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- Ensure Seed Jobs - creates Seed Jobs and ensures that all of them have been successfully executed
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- Ensure User Configuration - executed user provided configuration, like groovy scripts, configuration as code or plugins
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- Ensure Backup Job - creates Backup job and ensures that backup has been successfully performed
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## Operator State
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Operator state is kept in custom resource status section, which is used for storing any configuration events or job statuses managed by the operator.
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It helps to maintain or recover desired state even after operator or Jenkins restarts.
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## System Jenkins Jobs
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The operator or Jenkins instance can be restarted at any time and any operation should not block the reconciliation loop.
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Taking this into account we implemented custom jobs API for executing system jobs (seed jobs, groovy scripts, etc.) according to the operator lifecycle.
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Main assumptions are:
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- do not block reconciliation loop
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- fire job, requeue reconciliation loop and verify job status next time
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- handle retries if case of failure
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- handle build expiration (deadline)
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- keep state in the custom resource status section
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## Jenkins Docker Images
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**Jenkins Operator** is fully compatible with **jenkins:lts** docker image and does not introduce any hidden changes there.
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If needed, the docker image can easily be changed in custom resource manifest as long as it supports standard Jenkins file system structure.
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