Only mark a proxy as bad if we have confirmation that another proxy succeeded for the same request.

net/proxy/proxy_list.cc

 // Copyright (c) 2006-2008 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/logging.h"
 #include "base/string_tokenizer.h"
 #include "base/time.h"
 #include "net/proxy/proxy_server.h"
@@ skipping 97 matching lines @@
   std::string proxy_list;
   std::vector<ProxyServer>::const_iterator iter = proxies_.begin();
   for (; iter != proxies_.end(); ++iter) {
     if (!proxy_list.empty())
       proxy_list += ";";
     proxy_list += iter->ToPacString();
   }
   return proxy_list.empty() ? std::string() : proxy_list;
 }
 
-bool ProxyList::Fallback(ProxyRetryInfoMap* proxy_retry_info) {
+bool ProxyList::Fallback(ProxyRetryInfoMap* proxy_retry_info,
+                         const BoundNetLog& net_log) {
   // Number of minutes to wait before retrying a bad proxy server.
   const TimeDelta kProxyRetryDelay = TimeDelta::FromMinutes(5);
 
   // TODO(eroman): It would be good if instead of removing failed proxies

[eroman, 2011/08/19 21:25:32]

My thinking in this comment was to do away with ProxyRetryInfoMap (since timing
isn't really relevant anymore), and just have ProxyList be a vector of proxy
choices (augmented by whether it was attempted and failed) along with a pointer
to the current location.

No need to change anything for this CL though, just thinking out loud.

   // from the list, we simply annotated them with the error code they failed
   // with. Of course, ProxyService::ReconsiderProxyAfterError() would need to
   // be given this information by the network transaction.
   //
   // The advantage of this approach is when the network transaction
   // fails, we could output the full list of proxies that were attempted, and
   // why each one of those failed (as opposed to just the last failure).
   //
   // And also, before failing the transaction wholesale, we could go back and
   // retry the "bad proxies" which we never tried to begin with.
@@ skipping 12 matching lines @@
     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,
+        make_scoped_refptr(new NetLogStringParameter("bad_proxy", key)));
   }
 
   // Remove this proxy from our list.
   proxies_.erase(proxies_.begin());
 
   return !proxies_.empty();
 }
 
 }  // namespace net