Google has warned about the discontinuation of support for the Server Push technology in Chrome 106, scheduled for September 27. The changes will also affect other browsers based on the Chromium codebase. Server Push technology is defined in the HTTP/2 and HTTP/3 standards, allowing the server to send resources to the client without waiting for explicit requests. This way, it is expected that the server can speed up page loading since the necessary files for rendering the page, such as CSS, scripts, and images, will have already been sent by the time the client requests them.
The reason cited for discontinuing support is the excessive complexity of implementing the technology in the presence of simpler and equally effective alternatives, such as the tag, which allows the browser to request a resource without waiting for it to be used on the page. On one hand, preload results in additional round-trip exchanges (RTT) compared to Server Push, but on the other hand, it avoids sending resources that are already in the browser cache. Overall, the differences in latency between using Server Push and preload are noted to be insignificant.
To initiate proactive loading on the client side server it is suggested to use HTTP response code 103, which allows informing the client about some HTTP headers immediately after the request, without waiting for the server to complete all related operations and begin delivering content. In this way, hints about elements associated with the delivered page can be communicated, which can be preloaded (for example, links to CSS and JavaScript used on the page). By receiving information about such resources, the browser can start loading them without waiting for the main page to finish delivering, reducing the overall request processing time.
In addition to optimizing resource loading, the Server Push It could also be used for streaming data from the server to the client, but for these purposes, the W3C consortium is developing the WebTransport protocol. The communication channel in WebTransport is organized over HTTP/3 using the QUIC protocol as transport. WebTransport offers advanced features, such as multi-stream transmission, unidirectional streams, out-of-order packet delivery, and both reliable and unreliable delivery modes.
According to Google statistics, Server Push technology has not gained widespread adoption. Although Server Push is included in the HTTP/3 specification, many server and client software products, including the Chrome browser, initially did not implement it. In 2021, about 1.25% of websites running on HTTP/2 used Server Push. This year, that figure has dropped to 0.7%.
Source: opennet.ru
