Lets use HTTP2

[sabino]

For now metabase uses HTTP 1.1

This change makes HTTP 2 requests possible.

Before

% curl -vso /dev/null --http2 http://localhost:3000                                                                                  18-06-04 - 18:03:31
* Rebuilt URL to: http://localhost:3000/
*   Trying ::1...
* TCP_NODELAY set
* Connected to localhost (::1) port 3000 (#0)
> GET / HTTP/1.1
> Host: localhost:3000
> User-Agent: curl/7.54.0
> Accept: */*
> Connection: Upgrade, HTTP2-Settings
> Upgrade: h2c
> HTTP2-Settings: AAMAAABkAARAAAAAAAIAAAAA
>
< HTTP/1.1 200 OK
< X-Frame-Options: DENY
< X-XSS-Protection: 1; mode=block
< Last-Modified: Mon, 04 Jun 2018 21:03:40 +0000
< Strict-Transport-Security: max-age=31536000
< X-Permitted-Cross-Domain-Policies: none
< Cache-Control: max-age=0, no-cache, must-revalidate, proxy-revalidate
< X-Content-Type-Options: nosniff
< Content-Security-Policy: default-src 'none'; script-src 'unsafe-inline' 'unsafe-eval' 'self' https://maps.google.com https://apis.google.com https://www.google-analytics.com https://*.googleapis.com *.gstatic.com https://js-agent.newrelic.com https://*.nr-data.net ; child-src 'self' https://accounts.google.com; style-src 'unsafe-inline' 'self' fonts.googleapis.com; font-src 'self' fonts.gstatic.com themes.googleusercontent.com ; img-src * 'self' data:; connect-src 'self' metabase.us10.list-manage.com https://*.nr-data.net ;
< Content-Type: text/html;charset=utf-8
< Expires: Tue, 03 Jul 2001 06:00:00 GMT
< Transfer-Encoding: chunked
< Server: Jetty(9.4.z-SNAPSHOT)
<
{ [15401 bytes data]
* Connection #0 to host localhost left intact

After

% curl -vso /dev/null --http2 http://localhost:3000                                                                                  18-06-04 - 18:03:40
* Rebuilt URL to: http://localhost:3000/
*   Trying ::1...
* TCP_NODELAY set
* Connected to localhost (::1) port 3000 (#0)
> GET / HTTP/1.1
> Host: localhost:3000
> User-Agent: curl/7.54.0
> Accept: */*
> Connection: Upgrade, HTTP2-Settings
> Upgrade: h2c
> HTTP2-Settings: AAMAAABkAARAAAAAAAIAAAAA
>
< HTTP/1.1 101 Switching Protocols
* Received 101
* Using HTTP2, server supports multi-use
* Connection state changed (HTTP/2 confirmed)
* Copying HTTP/2 data in stream buffer to connection buffer after upgrade: len=0
* Connection state changed (MAX_CONCURRENT_STREAMS updated)!
< HTTP/2 200
< server: Jetty(9.4.z-SNAPSHOT)
< x-frame-options: DENY
< x-xss-protection: 1; mode=block
< last-modified: Mon, 04 Jun 2018 21:10:23 +0000
< strict-transport-security: max-age=31536000
< x-permitted-cross-domain-policies: none
< cache-control: max-age=0, no-cache, must-revalidate, proxy-revalidate
< x-content-type-options: nosniff
< content-security-policy: default-src 'none'; script-src 'unsafe-inline' 'unsafe-eval' 'self' https://maps.google.com https://apis.google.com https://www.google-analytics.com https://*.googleapis.com *.gstatic.com https://js-agent.newrelic.com https://*.nr-data.net ; child-src 'self' https://accounts.google.com; style-src 'unsafe-inline' 'self' fonts.googleapis.com; font-src 'self' fonts.gstatic.com themes.googleusercontent.com ; img-src * 'self' data:; connect-src 'self' metabase.us10.list-manage.com https://*.nr-data.net ;
< content-type: text/html;charset=utf-8
< expires: Tue, 03 Jul 2001 06:00:00 GMT
<
{ [16384 bytes data]
* 16366 data bytes written
{ [16366 bytes data]
* Connection #0 to host localhost left intact

Possibly
Fixes #6385

Before submitting the PR, please make sure you do the following

• If there are changes to the backend codebase, run the backend tests with lein test && lein eastwood && lein bikeshed && lein docstring-checker && ./bin/reflection-linter
• Run the frontend and integration tests with yarn lint && yarn flow && yarn test)
• Sign the Contributor License Agreement
  (unless it's a tiny documentation change).

[tlrobinson]

@camsaul @senior thoughts on this?

[camsaul]

Hey @sabino, thanks for this PR. We're looking forward to enabling HTTP 2 support, but we'd rather wait until it's supported upstream by Ring instead of switching to an unofficial fork.

Please feel free to open a new PR to enable HTTP 2 support when it's possible to do so using the official Ring dependency. Thanks again

[sabino]

Hey @camsaul
Looks like the official ring adapter doesn't support HTTP2 yet because that would require updating the jetty version, and would make it incompatible with older JVMs.

ring-clojure/ring#127

Since metabase already dropped support for Java 7, do you really think it's a problem to use a third-party library? This library has been around since 2013.

I've opened an issue myself:
ring-clojure/ring#331