net/dns/host_cache.cc

   1 // Copyright (c) 2012 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/dns/host_cache.h"
   6
   7 #include "base/logging.h"
   8 #include "base/metrics/field_trial.h"
   9 #include "base/metrics/histogram_macros.h"
  10 #include "base/strings/string_number_conversions.h"
  11 #include "net/base/net_errors.h"
  12
  13 namespace net {
  14
  15 //-----------------------------------------------------------------------------
  16
  17 HostCache::Entry::Entry(int error, const AddressList& addrlist,
  18                         base::TimeDelta ttl)
  19     : error(error),
  20       addrlist(addrlist),
  21       ttl(ttl) {
  22   DCHECK(ttl >= base::TimeDelta());
  23 }
  24
  25 HostCache::Entry::Entry(int error, const AddressList& addrlist)
  26     : error(error),
  27       addrlist(addrlist),
  28       ttl(base::TimeDelta::FromSeconds(-1)) {
  29 }
  30
  31 HostCache::Entry::~Entry() {
  32 }
  33
  34 //-----------------------------------------------------------------------------
  35
  36 HostCache::HostCache(size_t max_entries)
  37     : entries_(max_entries) {
  38 }
  39
  40 HostCache::~HostCache() {
  41 }
  42
  43 const HostCache::Entry* HostCache::Lookup(const Key& key,
  44                                           base::TimeTicks now) {
  45   DCHECK(CalledOnValidThread());
  46   if (caching_is_disabled())
  47     return NULL;
  48
  49   return entries_.Get(key, now);
  50 }
  51
  52 void HostCache::Set(const Key& key,
  53                     const Entry& entry,
  54                     base::TimeTicks now,
  55                     base::TimeDelta ttl) {
  56   DCHECK(CalledOnValidThread());
  57   if (caching_is_disabled())
  58     return;
  59
  60   entries_.Put(key, entry, now, now + ttl);
  61 }
  62
  63 void HostCache::clear() {
  64   DCHECK(CalledOnValidThread());
  65   entries_.Clear();
  66 }
  67
  68 size_t HostCache::size() const {
  69   DCHECK(CalledOnValidThread());
  70   return entries_.size();
  71 }
  72
  73 size_t HostCache::max_entries() const {
  74   DCHECK(CalledOnValidThread());
  75   return entries_.max_entries();
  76 }
  77
  78 // Note that this map may contain expired entries.
  79 const HostCache::EntryMap& HostCache::entries() const {
  80   DCHECK(CalledOnValidThread());
  81   return entries_;
  82 }
  83
  84 // static
  85 scoped_ptr<HostCache> HostCache::CreateDefaultCache() {
  86   // Cache capacity is determined by the field trial.
  87 #if defined(ENABLE_BUILT_IN_DNS)
  88   const size_t kDefaultMaxEntries = 1000;
  89 #else
  90   const size_t kDefaultMaxEntries = 100;
  91 #endif
  92   const size_t kSaneMaxEntries = 1 << 20;
  93   size_t max_entries = 0;
  94   base::StringToSizeT(base::FieldTrialList::FindFullName("HostCacheSize"),
  95                       &max_entries);
  96   if ((max_entries == 0) || (max_entries > kSaneMaxEntries))
  97     max_entries = kDefaultMaxEntries;
  98   return make_scoped_ptr(new HostCache(max_entries));
  99 }
 100
 101 void HostCache::EvictionHandler::Handle(
 102     const Key& key,
 103     const Entry& entry,
 104     const base::TimeTicks& expiration,
 105     const base::TimeTicks& now,
 106     bool on_get) const {
 107   if (on_get) {
 108     DCHECK(now >= expiration);
 109     UMA_HISTOGRAM_CUSTOM_TIMES("DNS.CacheExpiredOnGet", now - expiration,
 110         base::TimeDelta::FromSeconds(1), base::TimeDelta::FromDays(1), 100);
 111     return;
 112   }
 113   if (expiration > now) {
 114     UMA_HISTOGRAM_CUSTOM_TIMES("DNS.CacheEvicted", expiration - now,
 115         base::TimeDelta::FromSeconds(1), base::TimeDelta::FromDays(1), 100);
 116   } else {
 117     UMA_HISTOGRAM_CUSTOM_TIMES("DNS.CacheExpired", now - expiration,
 118         base::TimeDelta::FromSeconds(1), base::TimeDelta::FromDays(1), 100);
 119   }
 120 }
 121
 122 }  // namespace net