njs and dynamic http2 server push

[CarterLi]

I am trying using njs to add Link header to enable dynamic http2 server push

// This code is based on the official example in http://nginx.org/en/docs/http/ngx_http_js_module.html
if (r.headersIn.cookie) {
    s += "Cookies:\n";
    var cookies = parse(r.headersIn.cookie); // https://github.com/jshttp/cookie/blob/master/index.js#L49
    for (var c in cookies) {
        s += "  cookie '" + c + "' is '" + cookies[c] + "'\n";
        r.headersOut.link = '</api/' + cookies[c] + '/test>; rel=preload; as=fetch; crossorigin';
    }
}

Which results in

$ nghttp -vs 'https://test.eoitek.net/summary' -H'cookie: a=1'                                 日  6/24 12:07:18 2018
[ERROR] Could not connect to the address ::1
Trying next address 127.0.0.1
[  0.009] Connected
The negotiated protocol: h2
[  0.011] recv SETTINGS frame <length=18, flags=0x00, stream_id=0>
          (niv=3)
          [SETTINGS_MAX_CONCURRENT_STREAMS(0x03):128]
          [SETTINGS_INITIAL_WINDOW_SIZE(0x04):65536]
          [SETTINGS_MAX_FRAME_SIZE(0x05):16777215]
[  0.012] recv WINDOW_UPDATE frame <length=4, flags=0x00, stream_id=0>
          (window_size_increment=2147418112)
[  0.012] send SETTINGS frame <length=12, flags=0x00, stream_id=0>
          (niv=2)
          [SETTINGS_MAX_CONCURRENT_STREAMS(0x03):100]
          [SETTINGS_INITIAL_WINDOW_SIZE(0x04):65535]
[  0.012] send SETTINGS frame <length=0, flags=0x01, stream_id=0>
          ; ACK
          (niv=0)
[  0.012] send PRIORITY frame <length=5, flags=0x00, stream_id=3>
          (dep_stream_id=0, weight=201, exclusive=0)
[  0.012] send PRIORITY frame <length=5, flags=0x00, stream_id=5>
          (dep_stream_id=0, weight=101, exclusive=0)
[  0.012] send PRIORITY frame <length=5, flags=0x00, stream_id=7>
          (dep_stream_id=0, weight=1, exclusive=0)
[  0.012] send PRIORITY frame <length=5, flags=0x00, stream_id=9>
          (dep_stream_id=7, weight=1, exclusive=0)
[  0.012] send PRIORITY frame <length=5, flags=0x00, stream_id=11>
          (dep_stream_id=3, weight=1, exclusive=0)
[  0.012] send HEADERS frame <length=50, flags=0x25, stream_id=13>
          ; END_STREAM | END_HEADERS | PRIORITY
          (padlen=0, dep_stream_id=11, weight=16, exclusive=0)
          ; Open new stream
          :method: GET
          :path: /summary
          :scheme: https
          :authority: test.eoitek.net
          accept: */*
          accept-encoding: gzip, deflate
          user-agent: nghttp2/1.32.0
          cookie: a=1
[  0.012] recv SETTINGS frame <length=0, flags=0x01, stream_id=0>
          ; ACK
          (niv=0)
[  0.012] recv (stream_id=13) :status: 200
[  0.012] recv (stream_id=13) server: nginx/1.15.0
[  0.012] recv (stream_id=13) date: Sun, 24 Jun 2018 04:08:06 GMT
[  0.012] recv (stream_id=13) content-type: text/plain
[  0.012] recv (stream_id=13) content-length: 327
[  0.012] recv (stream_id=13) link: </api/1/test>; rel=preload; as=fetch; crossorigin
[  0.012] recv HEADERS frame <length=124, flags=0x04, stream_id=13>
          ; END_HEADERS
          (padlen=0)
          ; First response header
JS summary

Method: GET
HTTP version: 1.1
Host: test.eoitek.net
Remote Address: 127.0.0.1
URI: /summary
Headers:
  header 'host' is 'test.eoitek.net'
  header 'accept' is '*/*'
  header 'accept-encoding' is 'gzip, deflate'
  header 'user-agent' is 'nghttp2/1.32.0'
  header 'cookie' is 'a=1'
Cookies:
  cookie 'a' is '1'
Args:
[  0.012] recv DATA frame <length=327, flags=0x01, stream_id=13>
          ; END_STREAM
[  0.012] send GOAWAY frame <length=8, flags=0x00, stream_id=0>
          (last_stream_id=0, error_code=NO_ERROR(0x00), opaque_data(0)=[])
***** Statistics *****

Request timing:
  responseEnd: the  time  when  last  byte of  response  was  received
               relative to connectEnd
 requestStart: the time  just before  first byte  of request  was sent
               relative  to connectEnd.   If  '*' is  shown, this  was
               pushed by server.
      process: responseEnd - requestStart
         code: HTTP status code
         size: number  of  bytes  received as  response  body  without
               inflation.
          URI: request URI

see http://www.w3.org/TR/resource-timing/#processing-model

sorted by 'complete'

id  responseEnd requestStart  process code size request path
 13      +855us       +238us    616us  200  327 /summary

The response header Link is added but no PUSH_PROMISE is given. I've set http2_push_preload on; and have tested add_header "Link ...", which works fine.

[xeioex]

The Link (a well as a couple of others) header should be treated in a special way inside nginx internal headers structure to work properly. Will be fixed soon.

[CarterLi]

@xeioex Could I push resources directly in njs without Link headers ( like http2_push url )? Sometimes browsers won't use pushed resources with Link headers for unknown reason

[xeioex]

@CarterLi No, currently it is not possible to push resources directly.

[xeioex]

FYI, HTTP/2 Push is dead.