netwerk/base/nsIClassOfService.idl

   1 /* This Source Code Form is subject to the terms of the Mozilla Public
   2  * License, v. 2.0. If a copy of the MPL was not distributed with this
   3  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   4
   5 #include "nsISupports.idl"
   6
   7 /**
   8  * nsIClassOfService.idl
   9  *
  10  * Used to express class dependencies and characteristics - complimentary to
  11  * nsISupportsPriority which is used to express weight
  12  *
  13  * Channels that implement this interface may make use of this
  14  * information in different ways.
  15  */
  16
  17 // convenience class for passing around the class of service
  18 %{C++
  19 namespace mozilla::net {
  20 class ClassOfService;
  21 }
  22 %}
  23 native ClassOfService(mozilla::net::ClassOfService);
  24
  25 [scriptable, uuid(1ccb58ec-5e07-4cf9-a30d-ac5490d23b41)]
  26 interface nsIClassOfService : nsISupports
  27 {
  28   attribute unsigned long classFlags;
  29   attribute bool incremental;
  30
  31   void clearClassFlags(in unsigned long flags);
  32   void addClassFlags(in unsigned long flags);
  33   void setClassOfService(in ClassOfService s);
  34
  35   // All these flags have a (de)prioritization effect.
  36
  37   // In the HTTP/1 world the priority is considered for all requests inside a so
  38   // called 'Request Context' which is a context common to all sub-resources
  39   // belonging to a single top level window (RequestContextService). Requests
  40   // marked with the Leader flag are blocking (preventing from being sent to the
  41   // server) all other resource loads except those marked with the Unblocked
  42   // flag.  Other classes run in parallel - neither being blocked no ;r blocking.
  43   // The Leader flag is used only for <head> blocking resources (sync and
  44   // defer javascript resources and stylesheets.) Purpose is to deliver these
  45   // first-paint and domcontentloaded blocking resources as soon as possbile.
  46
  47   // In the HTTP/2 world it's different. Priorities are done only per HTTP/2
  48   // session, normally we have one session per one origin (including origin
  49   // attributes!) Requests are dispatched (sent) immediately on an HTTP/2
  50   // session. Each session has artificial streams (groups) relating to the class
  51   // of service flags (Leader, Other, Background, Speculative, Follower,
  52   // UrgentStart), each such a stream is given a different weight (only way to
  53   // give a stream a priority in HTTP/2) reflecting the desired request group
  54   // priority.  Actual request streams are then dependent on these artificial
  55   // streams (groups). nsISupportsPriority of each request is passed as a weight
  56   // on the HTTP/2 stream to prioritize streams in the same group. A stream can
  57   // also be dependent on other stream. We have dependency of Followers on
  58   // Leaders, hence everything set the Follower flag should be processed by the
  59   // server after Leaders. Same for Speculative being dependent on Background. The
  60   // tree is created and used here:
  61   // https://searchfox.org/mozilla-central/rev/cc280c4be94ff8cf64a27cc9b3d6831ffa49fa45/netwerk/protocol/http/Http2Session.cpp#1053-1070
  62   // https://searchfox.org/mozilla-central/rev/cc280c4be94ff8cf64a27cc9b3d6831ffa49fa45/netwerk/protocol/http/Http2Stream.cpp#1338
  63   // For detailed description of how HTTP/2 server should handle the priorities
  64   // and dependencies see:
  65   // https://developers.google.com/web/fundamentals/performance/http2/#stream_prioritization
  66   // Please note that the dependecies and weights we are sending to the server
  67   // are only suggestions, the server may completely ignore it.
  68
  69   // Leaders (should) block all other resources except Unblocked.  This flag
  70   // also priortizes HTTP cache reading queue by blocking all other cache
  71   // requests.
  72   const unsigned long Leader = 1 << 0;
  73   // The Follower flag is currently unused!
  74   const unsigned long Follower = 1 << 1;
  75   // The Speculative flag is currently unused!
  76   const unsigned long Speculative = 1 << 2;
  77   // The Background flag is currently only used for Beacon.
  78   const unsigned long Background = 1 << 3;
  79   // Requests marked with this flag are not blocked by Leaders.  This is mainly
  80   // used for probing-like XMLHttpRequests that may block delivery of head
  81   // blocking resources, e.g. CSS files tailored for the UA.
  82   const unsigned long Unblocked = 1 << 4;
  83   // Throttleable flag allows response throttling of the resource load. Note
  84   // that this functionality is currently disabled.
  85   const unsigned long Throttleable = 1 << 5;
  86   // UrgentStart makes the request temporarily extend HTTP/1 connection
  87   // parallelism limits.  Used mainly for navigational requests (top level html)
  88   // and any request considered coming from a user interaction to make reaction
  89   // of the browser as fast as possible and not blocked.
  90   const unsigned long UrgentStart = 1 << 6;
  91   // Specifically disables throttling under any circumstances, used for media
  92   // responses mainly.
  93   const unsigned long DontThrottle = 1 << 7;
  94   // Enforce tailing on this load; any of Leader, Unblocked, UrgentStart,
  95   // TailForbidden overrule this flag (disable tailing.)
  96   const unsigned long Tail = 1 << 8;
  97   // Tailing may be engaged regardless if the load is marked Unblocked when some
  98   // other conditions are met later, like when the load is found to be a
  99   // tracker.
 100   const unsigned long TailAllowed = 1 << 9;
 101   // Tailing not allowed under any circumstances or combination of flags.
 102   const unsigned long TailForbidden = 1 << 10;
 103 };