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HTTP/2 Server Push Directives Land in Nginx 1.13.9

The open source Nginx 1.13.9 web server debuted today, providing support for a new HTTP/2 standard feature known as Server Push.

The HTTP/2 web standard was completed three years ago in February 2015, with Nginx ahead of the curve in terms of HTTP/2 standard adoption. The NGINX Plus R7 release in September 2015 featured the first commercially supported enterprise-grade support provided by Nginx for HTTP/2.

http2_push and http2_push_preload Directives Debut in Nginx 1.13.9

As is the case with many web standards, HTTP/2 includes multiple components. Nginx 1.13.9While both the open-source and commercial versions of Nginx had provided support for many elements of HTTP/2, the 1.13.9 release is the first to integrate the "http2_push" and "http2_push_preload" directives.

"HTTP/2 allows a server to pre-emptively send (or 'push') responses (along with corresponding 'promised' requests) to a client in association with a previous client-initiated request," the IETF RFC for HTTP/2 states. "This can be useful when the server knows the client will need to have those responses available in order to fully process the response to the original request."

According to multiple sets of tests conducted by Nginx, Server Push can have a tangible impact on web server performance in certain circumstances. In a blog post, Owen Garrett, head of products at Nginx Inc, wrote that the the net savings from preload may be one Round Trip Time (RTT) or more. An RTT is the time it takes for a server to receive a request and respond to the end user.

"If you can identify which resources are required in advance, there’s a real benefit in having upstream servers send a preload hint," Garret wrote. "The additional benefit of pushing these resources is small but measurable, but may possibly result in wasted bandwidth and delays for needed resources. You should test and monitor any push configurations carefully."

The HTTP/2 Server Push support is only available in the open source branch of Nginx at this time, with full commercial support expected to debut in the NGINX Plus R15 release, which is currently set to become generally available in April 2018.

Sean Michael Kerner is a senior editor at ServerWatch and InternetNews.com. Follow him on Twitter @TechJournalist.

This article was originally published on February 20, 2018
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