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      1 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #include "net/socket/stream_socket.h"
      6 
      7 #include "base/metrics/field_trial.h"
      8 #include "base/metrics/histogram.h"
      9 #include "base/strings/string_number_conversions.h"
     10 #include "base/values.h"
     11 
     12 namespace net {
     13 
     14 StreamSocket::UseHistory::UseHistory()
     15     : was_ever_connected_(false),
     16       was_used_to_convey_data_(false),
     17       omnibox_speculation_(false),
     18       subresource_speculation_(false) {
     19 }
     20 
     21 StreamSocket::UseHistory::~UseHistory() {
     22   EmitPreconnectionHistograms();
     23 }
     24 
     25 void StreamSocket::UseHistory::Reset() {
     26   EmitPreconnectionHistograms();
     27   was_ever_connected_ = false;
     28   was_used_to_convey_data_ = false;
     29   // omnibox_speculation_ and subresource_speculation_ values
     30   // are intentionally preserved.
     31 }
     32 
     33 void StreamSocket::UseHistory::set_was_ever_connected() {
     34   DCHECK(!was_used_to_convey_data_);
     35   was_ever_connected_ = true;
     36 }
     37 
     38 void StreamSocket::UseHistory::set_was_used_to_convey_data() {
     39   DCHECK(was_ever_connected_);
     40   was_used_to_convey_data_ = true;
     41 }
     42 
     43 
     44 void StreamSocket::UseHistory::set_subresource_speculation() {
     45   DCHECK(was_ever_connected_);
     46   // TODO(jar): We should transition to marking a socket (or stream) at
     47   // construction time as being created for speculative reasons.  This current
     48   // approach of trying to track use of a socket to convey data can make
     49   // mistakes when other sockets (such as ones sitting in the pool for a long
     50   // time) are issued.  Unused sockets can be left over when a when a set of
     51   // connections to a host are made, and one is "unlucky" and takes so long to
     52   // complete a connection, that another socket is used, and recycled before a
     53   // second connection comes available.  Similarly, re-try connections can leave
     54   // an original (slow to connect socket) in the pool, and that can be issued
     55   // to a speculative requester. In any cases such old sockets will fail when an
     56   // attempt is made to used them!... and then it will look like a speculative
     57   // socket was discarded without any user!?!?!
     58   if (was_used_to_convey_data_)
     59     return;
     60   subresource_speculation_ = true;
     61 }
     62 
     63 void StreamSocket::UseHistory::set_omnibox_speculation() {
     64   DCHECK(was_ever_connected_);
     65   if (was_used_to_convey_data_)
     66     return;
     67   omnibox_speculation_ = true;
     68 }
     69 
     70 bool StreamSocket::UseHistory::was_used_to_convey_data() const {
     71   DCHECK(!was_used_to_convey_data_ || was_ever_connected_);
     72   return was_used_to_convey_data_;
     73 }
     74 
     75 void StreamSocket::UseHistory::EmitPreconnectionHistograms() const {
     76   DCHECK(!subresource_speculation_ || !omnibox_speculation_);
     77   // 0 ==> non-speculative, never connected.
     78   // 1 ==> non-speculative never used (but connected).
     79   // 2 ==> non-speculative and used.
     80   // 3 ==> omnibox_speculative never connected.
     81   // 4 ==> omnibox_speculative never used (but connected).
     82   // 5 ==> omnibox_speculative and used.
     83   // 6 ==> subresource_speculative never connected.
     84   // 7 ==> subresource_speculative never used (but connected).
     85   // 8 ==> subresource_speculative and used.
     86   int result;
     87   if (was_used_to_convey_data_)
     88     result = 2;
     89   else if (was_ever_connected_)
     90     result = 1;
     91   else
     92     result = 0;  // Never used, and not really connected.
     93 
     94   if (omnibox_speculation_)
     95     result += 3;
     96   else if (subresource_speculation_)
     97     result += 6;
     98   UMA_HISTOGRAM_ENUMERATION("Net.PreconnectUtilization2", result, 9);
     99 }
    100 
    101 }  // namespace net
    102