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By: Renu M

What Are the Benefits of Owl Concurrent Mode in Odoo 16

Technical Odoo 16 Odoo Enterprises Odoo Community

In the world of web development, building highly concurrent applications that deliver exceptional user experiences is crucial. Owl, a cutting-edge JavaScript framework, addresses this need by offering asynchronous rendering capabilities right from its inception. By leveraging Owl's asynchronous components, developers can create complex applications that optimize performance and provide a seamless user experience. In this blog post, we will explore Owl's concurrent mode, delve into the benefits it offers, and understand how it manages the inherent complexity of asynchrony.

Benefits of Owl's Concurrent Mode

Owl's concurrent mode unlocks several advantages that empower developers to build feature-rich applications:
Delayed Rendering: Owl allows developers to defer rendering until asynchronous operations, such as data fetching or API requests, are complete. This ensures that the application remains responsive and the user interface is only updated when all required data is available.
Lazy Loading: With Owl's concurrent mode, it becomes possible to lazily load libraries or components while keeping the existing screen fully functional. This results in faster initial page loads and improved overall performance.
Performance Optimization: Owl leverages concurrent rendering to apply the results of multiple renderings in a single animation frame. By batching updates, Owl minimizes unnecessary re-renders and improves performance by updating the DOM efficiently.
Rendering Control: Owl provides mechanisms to cancel, restart, or reuse renderings based on their relevance. This ensures that the application stays responsive and delivers the most up-to-date content without unnecessary overhead.

Understanding the Rendering Process

To grasp Owl's asynchronous rendering model, let's dive into the two phases involved in rendering components:

Virtual Rendering:

During this phase, Owl renders the component's template in memory, creating a virtual representation of the desired HTML structure. The output of this phase is a virtual DOM.
Virtual rendering is an asynchronous process that involves invoking lifecycle hooks like willStart and willUpdateProps on each subcomponent. These hooks handle the creation and updating of subcomponents.
The virtual rendering process is recursive, as each component acts as the root of its own component tree, necessitating the rendering of subcomponents.


Once the virtual rendering is complete, the rendered component is applied synchronously to the real DOM during the next animation frame.
The patching phase involves synchronously updating the entire component tree in the DOM, ensuring that the user interface reflects the changes made during virtual rendering.

Managing Asynchrony and Complexity

While Owl's asynchronous rendering offers numerous benefits, it also introduces additional complexity. Two common challenges arise when working with asynchronous components:
Delayed Rendering: Any component in the application can potentially delay the rendering of the entire application, making it crucial to handle such scenarios carefully. Developers should ensure that the application remains responsive even during extended asynchronous operations.
Handling State and Props Changes: For a given component, asynchronous rerendering can be triggered by changes in both its state and props. However, these changes may occur at different times, posing a challenge for reconciling the resulting renderings. Careful consideration is required to synchronize and manage state and props updates effectively.

Tips for Working with Asynchronous Components

To effectively work with asynchronous components in Owl, consider the following tips:
Minimize Asynchronous Components: While asynchronous rendering is powerful, it's important to minimize its usage. Only employ asynchronous components when necessary, such as for lazy loading external libraries.
Handle Asynchronous Operations Thoughtfully: When dealing with asynchronous operations, ensure that the application remains responsive by providing appropriate feedback to users. Utilize loading indicators or placeholders to inform users of ongoing operations.
Plan for State and Props Changes: Understand the potential interactions between state and props changes. Carefully design your components to handle different scenarios, ensuring that updates are properly synchronized and reconciled.
Owl's asynchronous rendering model revolutionizes the development of concurrent applications by providing delayed rendering, lazy loading capabilities, and performance optimizations. While asynchronous rendering adds complexity, Owl offers mechanisms to manage it effectively. By understanding Owl's rendering process, managing asynchrony, and following best practices, developers can leverage the full potential of Owl and deliver exceptional user experiences.
To read more about the owl reactivity system in Odoo 16, refer to our blog An Overview of Owl Reactivity System in Odoo 16

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