Py-priority1

Pure-Python implementation of the HTTP/2 priority tree

Priority is a pure-Python implementation of the priority logic for HTTP/2, set out in RFC 7540 Section 5.3 Stream Priority. This logic allows for clients to express a preference for how the server allocates its limited resources to the many outstanding HTTP requests that may be running over a single HTTP/2 connection.

Specifically, this Python implementation uses a variant of the implementation used in the excellent H2O project. This original implementation is also the inspiration for nghttp2’s priority implementation, and generally produces a very clean and even priority stream. The only notable changes from H2O’s implementation are small modifications to allow the priority implementation to work cleanly as a separate implementation, rather than being embedded in a HTTP/2 stack directly.

While priority information in HTTP/2 is only a suggestion, rather than an enforceable constraint, where possible servers should respect the priority requests of their clients.