Envoy Etag Filter

• add unit tests

Build

First follow the setup instructions in Envoy to install dependencies. Then instead of building //source/exe:envoy-static, do

$ bazel build //:envoy

NOTE if zlib fails to build, check log of bazel-out/host/bin/external/envoy/bazel/foreign_cc/zlib/logs/CMake.log. If the log states cmake: command not found, then you'll need to symlink cmake and ninja to /usr/local/bin (mine are installed via homebrew to /opt/homebrew/bin)

$ sudo ln -s $(which cmake) /usr/local/bin/cmake
$ sudo ln -s $(which ninja) /usr/local/bin/ninja

Usage

There currently are no supported configuration options so usage is quite simple:

http_filters:
  - name: etag
  - name: envoy.router

TODO

• Support weak matching (ETag: W/"0815")
• Support range - For GET and HEAD methods, used in combination with an Range header, it can guarantee that the new ranges requested comes from the same resource than the previous one. If it doesn't match, then a 416 (Range Not Satisfiable) response is returned.
• Support generating Etags on the fly using a configuratble hash algorithm

Resources

• https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/If-Match
• https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/If-None-Match
• https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/ETag
• https://tools.ietf.org/html/rfc7232#section-2.3
• https://tools.ietf.org/html/rfc7232#section-3.1
• https://tools.ietf.org/html/rfc7232#section-3.2