fix(@angular/ssr): avoid retaining rendered HTML in memory post-request #31278

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alan-agius4 merged 1 commit into angular:main from alan-agius4:fix-ssr-leak

Sep 23, 2025

Merged

fix(@angular/ssr): avoid retaining rendered HTML in memory post-request #31278

alan-agius4 merged 1 commit into angular:main from alan-agius4:fix-ssr-leak

Sep 23, 2025

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@alan-agius4 alan-agius4 commented Sep 23, 2025

The previous implementation for server-side rendering could lead to memory leaks where the rendered HTML content was not properly garbage-collected after the HTTP request was fulfilled.

This was caused by inefficiencies in the critical CSS caching and how the response stream was handled. This commit addresses the issue by:

Refactoring the criticalCssLRUCache to store Uint8Array directly and use a more robust caching strategy.
Using the request URL as the cache key to prevent storing multiple cache entries for the same resource.
Ensuring the response stream controller enqueues the final HTML as a Uint8Array, avoiding unnecessary string conversions and dangling references.

These changes prevent the SSR response from being retained in memory, improving the stability and performance of the server.

Closes #31277

@angular-robot angular-robot bot added the area: @angular/ssr label

Sep 23, 2025

@alan-agius4 alan-agius4 force-pushed the fix-ssr-leak branch from 9099c4d to 3d8e0af Compare

September 23, 2025 10:01

@alan-agius4 alan-agius4 requested a review from jkrems

September 23, 2025 10:03

@alan-agius4 alan-agius4 marked this pull request as ready for review

September 23, 2025 10:03

@alan-agius4 alan-agius4 added action: review target: patch labels

Sep 23, 2025

@alan-agius4 alan-agius4 force-pushed the fix-ssr-leak branch 2 times, most recently from 4f42a51 to 4386931 Compare

September 23, 2025 10:22

@alan-agius4


 fix(@angular/ssr): avoid retaining rendered HTML in memory post-request

a4d1613

The previous implementation for server-side rendering could lead to memory leaks where the rendered HTML content was not properly garbage-collected after the HTTP request was fulfilled.
This was caused by inefficiencies in the critical CSS caching and how the response stream was handled. This commit addresses the issue by:
1. Refactoring the `criticalCssLRUCache` to store `Uint8Array` directly and use a more robust caching strategy.
2. Using the request URL as the cache key to prevent storing multiple cache entries for the same resource.
3. Ensuring the response stream controller enqueues the final HTML as a `Uint8Array`, avoiding unnecessary string conversions and dangling references.
These changes prevent the SSR response from being retained in memory, improving the stability and performance of the server.
Closes angular#31277