Streaming injections #212
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Streaming injections #212
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…vely close connections when clients' or servers' transmit the intention to do so themselves
…ut having to first read for the entire body
AitakattaSora
approved these changes
Jan 23, 2025
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What does this PR do?
Introduces streaming for HTML HTTP responses.
Currently, injecting CSS/JS into HTML responses requires us to read the entire response body first. This negates many browser performance optimizations, such as the ability to load external resources in parallel with the main document and do speculative parsing.
This change makes use of Go's
io.Pipeandhtml.Tokenizerto enable non-blocking, on-the-fly modifications of HTML responses. HTML is also no longer matched via regular expressions, which evidently were a bottleneck. This significantly improves performance for end users by allowing browsers to better utilize their optimizations.Additionally, this PR introduces a more accurate method for handling hop-to-hop headers during CONNECT proxying. For more details, see this comment.
How did you verify your code works?
htmlrewritefunctions.Previously:
"Waiting" takes most of the load time.
External resources only begin downloading after the document is fully fetched.
Now:
TTFB is improved 3x (the initial delay is almost entirely due to round-trip time). Full page loads are 1.5-2x faster on average.
External resources start fetching almost immediately after the page starts getting received.