Reconciliation
Reconciliation is the process of comparing related states, records, or outputs to identify differences and, when needed, resolve them or bring them into agreement.
Build a Frontend Web Framework (From Scratch)
The process of finding differences between two virtual DOM trees.
- How it is used
- Updates the browser’s DOM after state changes by comparing the current and new virtual DOM trees.
- How deep it goes
- Works through object and array diff helpers, then defines recursive node comparison and DOM patching steps.
- Examples
- Uses shopping-list changes, a worked array-operation sequence, and DOM inspection of a TODOs input.
- What you can do after
- Build it from scratch with diff helpers and patchDOM(), then diagnose unnecessary DOM changes in browser developer tools.
Read how Build a Frontend Web Framework (From Scratch) explains reconciliation →
Infrastructure as Code, Patterns and Practices: With examples in Python and Terraform
The process of bringing recorded or desired infrastructure configuration into agreement with the actual infrastructure state.
- How it is used
- Uses infrastructure as code to repair drift and align testing, production, and recorded configuration after failed or manual changes.
- How deep it goes
- Reconstructs manual state, encodes it in IaC, tests it, and applies it; it defers provider-specific transformation tooling.
- Examples
- Demonstrates proxy installation, startup scripts, testing-production comparison, application configuration, and firewall-rule investigation.
- What you can do after
- Diagnose/debug with it by locating drift and environment differences, then implement and verify an IaC-based corrective change.
Effective Platform Engineering
A reconciliation loop repeatedly compares desired and observed state and takes actions to make the observed state converge on the desired state.
- How it is used
- Uses continuous state correction to maintain repository integrations and automate platform tasks.
- How deep it goes
- Explains the loop’s operational role but does not detail its comparison algorithm, scheduling, or failure handling.
- Examples
- Uses a CLI repository-integration command and an API that checks, creates, and maintains repository connections.
- What you can do after
- Understand how platform automation can maintain an integration after its initial repository setup.
Read how Effective Platform Engineering explains reconciliation →
Automating API Delivery
Continuous reconciliation is the repeated comparison and correction of deployed state against a declared configuration state.
- How it is used
- Uses software agents to keep API gateway configuration aligned with Git-defined desired state across runtime environments.
- How deep it goes
- Explains declarative storage, drift detection, alerts, automatic correction, Git review, and rollback without specifying agent implementation details.
- Examples
- Uses API gateway drift, prohibited administration-UI changes, reviewed Git pull requests, agent redeployment, and git revert rollback.
- What you can do after
- Operate a Git-driven API configuration workflow that detects drift, restores declared state, and rolls back faulty configuration.
Learn Docker in a Month of Lunches, Second Edition
A reconciliation loop is a control loop that repeatedly compares current system state with desired state and takes corrective action.
- How it is used
- Uses reconciliation to keep Kubernetes Deployments aligned with declared Pod counts and maintain resilient application traffic.
- How deep it goes
- Explains the control-loop behavior through Pod replacement and endpoint updates, without descending into controller internals.
- Examples
- Demonstrates Pod deletion, automatic replacement, scaling to three replicas, endpoint updates, and traffic distribution.
- What you can do after
- Operate/configure Deployments and verify reconciliation by deleting Pods, scaling replicas, and inspecting replacement endpoints.
Read how Learn Docker in a Month of Lunches, Second Edition explains reconciliation →
Kubernetes in Action, Second Edition
A reconciliation loop is a repeated control process that compares observed state with desired state and makes corrective changes.
- How it is used
- Maintains Kubernetes workloads by continuously correcting differences between desired configurations and observed resources.
- How deep it goes
- Explains observation, comparison, creation, deletion, and repeated correction, but does not detail controller implementation internals.
- Examples
- Uses ReplicaSet replica counts, DaemonSet per-node pods, and an operator-managed MongoDB deployment as concrete examples.
- What you can do after
- Apply via kubectl by changing desired Kubernetes objects and observing controllers create, remove, or resize dependent resources.
Read how Kubernetes in Action, Second Edition explains reconciliation →
Terraform in Depth: Infrastructure as Code with Terraform and OpenTofu
Reconciliation is the repeated process of comparing actual system state with desired state and applying changes to reduce their difference.
- How it is used
- Uses Terraform and delivery systems to keep running infrastructure aligned with declarative configuration.
- How deep it goes
- Explains desired state, drift, planning, correction, scheduling, and human-review tradeoffs, but not reconciliation internals.
- Examples
- Uses Terraform plans, Git repositories, scheduled runs, pull requests, merges, and Slack drift notifications.
- What you can do after
- Diagnose drift with Terraform plans and apply or review corrections through an automated delivery system.
Related concepts
- Document Object Modeluses · The Document Object Model (DOM) is a standard programming interface that represents a document as a structured tree of objects and provides ways to access and modify its content and structure.
- virtual DOMuses · A virtual DOM is an in-memory user-interface tree that frameworks compare or process to determine updates to the rendered DOM.
- driftaddresses · Drift is a change over time in a system’s behavior, state, data, or configuration relative to a reference or expected baseline.
- GitOpspart of · GitOps is an operational approach that uses version-controlled declarative configuration as the source of truth and automation to apply or reconcile system state.
- React keyconfigured by · A React key is a stable identifier assigned to an element in a rendered collection so React can distinguish sibling elements across updates.
These guides are generated from the text of Manning books by Manning's knowledge graph and link to the sections they draw on. The full books are available on liveBook and at manning.com.