dhttp: A simple production-ready HTTP server library for the 2020s

[LukeShu]

A while back, because of a test flake that @thallgren noticed, I became aware of a bug in the x/net/http2/h2c library, which I subsequently submitted a fix for. However, while figuring out that bug, I became aware of a growing amount of things that were "wrong", in deep-seated architectural ways I couldn't just file a PR for. It became apparent to me that using *http.Server was simply unacceptable if you're doing h2c (cleartext HTTP/2... every one of our products does h2c all over the place), in a way that couldn't be fixed without changing the API.

So, I introduce *github.com/datawire/dlib/dhttp.ServerConfig, a replacement for *net/http.Server (it still ultimately uses an *http.Server internally, but that's an implementation detail).

The godoc has a lot better introduction/rationale.

Each of the TextXXX functions that I added corresponds to an actual bug in either Telepresence or AES or both.

To review

I suggest first reading the final godocs, to get the big picture. Then review the implementation commit-by-commit (if you even want to review the implementation).

Because of import-cycle reasons, I created derror, and moved PanicToError to there from dutil. This means that dutil now only exists for backward compatibility with older versions of dlib.

$ COLUMNS=80 git diff --stat lukeshu/misc HEAD -- :!*_test.go :!*_bundle.go                                                                                                                                                                               
 .circleci/.gitignore      |   1 +
 .circleci/bundle.d/go.mod |   5 +
 .circleci/bundle.d/go.sum |  26 ++++
 .circleci/bundle.d/pin.go |   5 +
 Makefile                  |   1 +
 derror/panic.go           |  81 ++++++++++
 dgroup/group.go           |   4 +-
 dhttp/Makefile            |  18 +++
 dhttp/server.go           | 371 ++++++++++++++++++++++++++++++++++++++++++++++
 dhttp/server_hijacked.go  |  75 ++++++++++
 dhttp/server_http2.go     |  65 ++++++++
 dutil/http_context.go     |  84 -----------
 dutil/http_server.go      | 132 +++++++++++++++++
 dutil/panic.go            |  80 +---------
 go.mod                    |   2 +-
 go.sum                    |  10 +-
 16 files changed, 796 insertions(+), 164 deletions(-)

[kflynn]

This looks really good, thanks!! My comments are pretty much entirely about docs and comments (shocking, I know) so let me preface the whole review by saying that I look forward to seeing Ambassador switch to using it. 🙂

Approving since everything I have can easily be addressed later.

[kflynn]

It makes me sad that the code switched from listener to ln for the variable name, instead of the docs changing from ln to listener. 😂

[thallgren]

Looks really good to me.