Randomize proxy timeout on Android over a range.

net/proxy/proxy_list.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 "net/proxy/proxy_list.h"
 
 #include "base/callback.h"
 #include "base/logging.h"
+#include "base/rand_util.h"
 #include "base/strings/string_tokenizer.h"
 #include "base/time.h"
 #include "base/values.h"
 #include "net/proxy/proxy_server.h"
 
 using base::TimeDelta;
 using base::TimeTicks;
 
 namespace net {
 
@@ skipping 167 matching lines @@
   }
   UpdateRetryInfoOnFallback(proxy_retry_info, net_log);
 
   // Remove this proxy from our list.
   proxies_.erase(proxies_.begin());
   return !proxies_.empty();
 }
 
 void ProxyList::UpdateRetryInfoOnFallback(
     ProxyRetryInfoMap* proxy_retry_info, const BoundNetLog& net_log) const {
-  // Number of minutes to wait before retrying a bad proxy server.
+  // Time to wait before retrying a bad proxy server.
 #if defined(OS_ANDROID)
-  const TimeDelta kProxyRetryDelay = TimeDelta::FromMinutes(1);
+  // Randomize the timeout over a range from one to five minutes.
+  const TimeDelta kProxyRetryDelay =
+      TimeDelta::FromMilliseconds(base::RandInt(1 * 60 * 1000, 5 * 60 * 1000));

[mmenke, 2013/05/08 16:50:08]

const Blah kBlah is generally only used for values that are always constant.  I
don't think I've ever seen it used for a randomized value, so this seems a
little weird.

I'm open to suggestions of prettier ways to do this.  If not, I'll think about
it and get back to you later (Probably today, possibly tomorrow).

[cbentzel, 2013/05/08 16:57:18]

proxy_retry_delay?

I don't think the const buys us much here.

[mmenke, 2013/05/08 16:58:58]

The nice thing about the const is that it draws attention to "Thar be hard-coded
constants here!"

I'm fine with that solution, though.

[bengr, 2013/05/08 17:23:11]

Yeah, I thought about three ways of writing this: (1) declare some constants,
which seemed liked overkill, considering the retry delay on line 203 isn't
declared that way; (2) use TimeDelta as a way of calling out that this is a
constant:
const TimeDelta kProxyRetryDelay =
    TimeDelta::FromMilliseconds(base::RandInt(
        TimeDelta::FromMinutes(1).InMilliseconds(),
        TimeDelta::FromMinutes(5).InMilliseconds()));
(3) what's in this CL.

 #else
   const TimeDelta kProxyRetryDelay = TimeDelta::FromMinutes(5);
 #endif
 
   if (proxies_.empty()) {
     NOTREACHED();
     return;
   }
 
   if (!proxies_[0].is_direct()) {
     std::string key = proxies_[0].ToURI();
     // Mark this proxy as bad.
     ProxyRetryInfoMap::iterator iter = proxy_retry_info->find(key);
     if (iter != proxy_retry_info->end()) {
       // TODO(nsylvain): This is not the first time we get this. We should
       // double the retry time. Bug 997660.
       iter->second.bad_until = TimeTicks::Now() + iter->second.current_delay;
     } else {
       ProxyRetryInfo retry_info;
       retry_info.current_delay = kProxyRetryDelay;
       retry_info.bad_until = TimeTicks().Now() + retry_info.current_delay;
       (*proxy_retry_info)[key] = retry_info;
     }
     net_log.AddEvent(NetLog::TYPE_PROXY_LIST_FALLBACK,
                      NetLog::StringCallback("bad_proxy", &key));
   }
 }
 
 }  // namespace net