Optimizing Angular Builds: Implementing Parallel Execution

Angular builds can become time-consuming, especially for large projects. This challenge focuses on improving build performance by leveraging parallel processing to execute independent build tasks concurrently. Successfully implementing parallel builds will significantly reduce overall build times, leading to faster development cycles and more efficient deployments.

Problem Description

Your task is to modify an Angular project's build process to execute independent build tasks in parallel. This involves identifying tasks that can be run concurrently and configuring the build system to manage their execution.

What needs to be achieved:

• Identify and isolate independent build tasks within an Angular project.
• Configure the Angular build process to execute these identified tasks in parallel.
• Ensure the final build output remains correct and consistent, regardless of the execution order or parallelism.

Key requirements:

• The solution should be implemented using TypeScript and standard Angular build tools (e.g., Angular CLI, Webpack).
• The parallelization should be applied to tasks that do not have interdependencies. For example, building different feature modules that are not actively referencing each other during the build phase.
• The solution must demonstrate a measurable reduction in build time compared to a sequential build.
• Error handling should be robust, ensuring that if one parallel task fails, the build process appropriately reports the failure and stops if necessary.

Expected behavior:

When the build process is initiated, multiple independent tasks (e.g., compilation of separate libraries, generation of specific assets) should start and run simultaneously. The build should complete successfully, producing the expected artifacts, and the total build time should be notably less than a standard sequential build.

Important edge cases to consider:

• Shared dependencies: If multiple parallel tasks rely on the same shared dependency that needs to be built or processed, ensure this dependency is handled correctly without race conditions or redundant processing.
• Resource contention: Consider scenarios where numerous parallel tasks might excessively consume CPU or memory, potentially leading to system instability or performance degradation. The solution should manage this gracefully.
• Complex project structures: The approach should be adaptable to projects with varying levels of modularity and inter-module dependencies.

Examples

Example 1:

Imagine an Angular project with two independent libraries, lib-a and lib-b, and a main application.

• Input: An Angular project structure with a defined angular.json configuration and source files for lib-a, lib-b, and the main app.
• Output: A successful build where the compilation of lib-a and lib-b occur concurrently. The final application build incorporates the compiled versions of these libraries.
• Explanation: Without parallelization, lib-a would build, then lib-b would build, and then the app would build. With parallelization, lib-a and lib-b build at the same time. The application build can only start after both libraries are complete.

Example 2:

Consider a scenario where building lib-a requires a specific configuration step that is independent of building lib-b.

• Input: A project with two libraries, lib-a and lib-b. lib-a has a pre-build script for generating mock data. lib-b has no such pre-build step.
• Output: The pre-build script for lib-a runs. Simultaneously, lib-b begins its build process. Once lib-a's pre-build script finishes, its compilation starts. The application build waits for both completed library builds.
• Explanation: The pre-build step for lib-a is an independent task that can be initiated early. While it's running, lib-b's build can commence, allowing for further overlap in execution.

Constraints

• The solution must be compatible with Angular CLI version 13 or later.
• The solution should focus on parallelizing build tasks that are inherently independent.
• The solution should not introduce significant overhead that negates the benefits of parallelization.
• The implementation should be primarily in TypeScript, leveraging existing Angular build infrastructure.
• Performance gains should be observable on a moderately sized Angular project (e.g., >50k lines of code, multiple libraries).

Notes

• Consider how to identify independent tasks. Are there specific configurations or project structures that make this easier?
• Explore how Angular CLI's build process or underlying tools like Webpack might offer hooks or configurations for parallel execution.
• Think about the trade-offs between fine-grained parallelization (e.g., parallelizing individual file compilations) and coarser-grained parallelization (e.g., parallelizing library builds).
• Document your approach and the observed performance improvements clearly.