Added a field trial (finch experiment) to disable SPDY for x% of users.

chrome/browser/io_thread.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/io_thread.h"
 
 #include <vector>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
@@ skipping 85 matching lines @@
 
 // The IOThread object must outlive any tasks posted to the IO thread before the
 // Quit task, so base::Bind() calls are not refcounted.
 
 namespace {
 
 const char kQuicFieldTrialName[] = "QUIC";
 const char kQuicFieldTrialEnabledGroupName[] = "Enabled";
 const char kQuicFieldTrialHttpsEnabledGroupName[] = "HttpsEnabled";
 
+const char kSpdyFieldTrialName[] = "SPDY";
+const char kSpdyFieldTrialDisabledGroupName[] = "SpdyDisabled";
+
 #if defined(OS_MACOSX) && !defined(OS_IOS)
 void ObserveKeychainEvents() {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   net::CertDatabase::GetInstance()->SetMessageLoopForKeychainEvents();
 }
 #endif
 
 // Used for the "system" URLRequestContext.
 class SystemURLRequestContext : public net::URLRequestContext {
  public:
@@ skipping 588 matching lines @@
           GetSwitchValueAsInt(command_line,
                               switches::kMaxSpdyConcurrentStreams));
     }
     if (command_line.HasSwitch(switches::kTrustedSpdyProxy)) {
       globals_->trusted_spdy_proxy.set(
           command_line.GetSwitchValueASCII(switches::kTrustedSpdyProxy));
     }
     if (command_line.HasSwitch(switches::kIgnoreUrlFetcherCertRequests))
       net::URLFetcher::SetIgnoreCertificateRequests(true);
 
+    std::string spdy_trial_group =
+        base::FieldTrialList::FindFullName(kSpdyFieldTrialName);
+
     if (command_line.HasSwitch(switches::kUseSpdy)) {

[Alexei Svitkine (slow), 2013/09/30 19:40:13]

Either add all of these flags to the config for the study, or call
FindFullName() only after you've checked all the flags that are not in the
config.

(Calling it marks the trial as "used" and therefore will be reported in
metrics.)

Alternatively, for flags that are not in the config, you can call Disable() on
the FieldTrial object returned by Find() to also disable reporting for that
trial.

[motek., 2013/09/30 20:44:29]

From the Department of Redundancy Department: pretty much what asvitkine@ wrote.


Do all these flags affect your experiment in any material way? If not, it might
be best to split the chain of ifs into a part affected by the study and the
rest. 

You may also want to single out the case where SPDY is disabled by policy and
FieldTrialList::Find()->Disable() it (not necessarily with this exact syntax
;-)).


On 2013/09/30 19:40:13, Alexei Svitkine wrote:

[ramant (doing other things), 2013/09/30 22:28:56]

Done.

[ramant (doing other things), 2013/09/30 22:28:56]

Done.

       std::string spdy_mode =
           command_line.GetSwitchValueASCII(switches::kUseSpdy);
       EnableSpdy(spdy_mode);
     } else if (command_line.HasSwitch(switches::kEnableHttp2Draft04)) {
       net::HttpStreamFactory::EnableNpnHttp2Draft04();
     } else if (command_line.HasSwitch(switches::kEnableSpdy4a2)) {
       net::HttpStreamFactory::EnableNpnSpdy4a2();
     } else if (command_line.HasSwitch(switches::kDisableSpdy31)) {
       net::HttpStreamFactory::EnableNpnSpdy3();
     } else if (command_line.HasSwitch(switches::kEnableNpn)) {
       net::HttpStreamFactory::EnableNpnSpdy();
     } else if (command_line.HasSwitch(switches::kEnableNpnHttpOnly)) {
       net::HttpStreamFactory::EnableNpnHttpOnly();
     } else {
-      // Use SPDY/3.1 by default.
-      net::HttpStreamFactory::EnableNpnSpdy31();
+      if (spdy_trial_group == kSpdyFieldTrialDisabledGroupName) {
+         net::HttpStreamFactory::set_spdy_enabled(false);
+      } else {
+        // Use SPDY/3.1 by default.
+        net::HttpStreamFactory::EnableNpnSpdy31();
+      }
     }
   }
 
   // TODO(rch): Make the client socket factory a per-network session
   // instance, constructed from a NetworkSession::Params, to allow us
   // to move this option to IOThread::Globals &
   // HttpNetworkSession::Params.
   if (command_line.HasSwitch(switches::kEnableTcpFastOpen))
     net::SetTCPFastOpenEnabled(true);
 }
@@ skipping 274 matching lines @@
   if (command_line.HasSwitch(switches::kDisableQuicHttps))
     return false;
 
   if (command_line.HasSwitch(switches::kEnableQuicHttps))
     return true;
 
   // HTTPS over QUIC should only be enabled if we are in the https
   // field trial group.
   return quic_trial_group == kQuicFieldTrialHttpsEnabledGroupName;
 }