Remove unused DNS.HostCache histograms

They're not used and this change can be easily reverted to add them back.

Bug: 908717
Bug: 906936
Change-Id: I81f866c7491a84c1c5b0c87c023d3e43cf9d3a8c
Reviewed-on: https://chromium-review.googlesource.com/c/1352330Reviewed-by: Misha Efimov <mef@chromium.org>
Reviewed-by: Jesse Doherty <jwd@chromium.org>
Commit-Queue: Paul Jensen <pauljensen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#611333}

net/dns/host_cache.cc

@@ -183,7 +183,6 @@ HostCache::HostCache(size_t max_entries)
 
 HostCache::~HostCache() {
   DCHECK_CALLED_ON_VALID_THREAD(thread_checker_);
-  RecordEraseAll(ERASE_DESTRUCT, tick_clock_->NowTicks());
 }
 
 const HostCache::Entry* HostCache::Lookup(const Key& key, base::TimeTicks now) {
@@ -192,17 +191,12 @@ const HostCache::Entry* HostCache::Lookup(const Key& key, base::TimeTicks now) {
     return nullptr;
 
   HostCache::Entry* entry = LookupInternal(key);
-  if (!entry) {
-    RecordLookup(LOOKUP_MISS_ABSENT, now, nullptr);
+  if (!entry)
     return nullptr;
-  }
-  if (entry->IsStale(now, network_changes_)) {
-    RecordLookup(LOOKUP_MISS_STALE, now, entry);
+  if (entry->IsStale(now, network_changes_))
     return nullptr;
-  }
 
   entry->CountHit(/* hit_is_stale= */ false);
-  RecordLookup(LOOKUP_HIT_VALID, now, entry);
   return entry;
 }
 
@@ -215,14 +209,11 @@ const HostCache::Entry* HostCache::LookupStale(
     return nullptr;
 
   HostCache::Entry* entry = LookupInternal(key);
-  if (!entry) {
-    RecordLookup(LOOKUP_MISS_ABSENT, now, nullptr);
+  if (!entry)
     return nullptr;
-  }
 
   bool is_stale = entry->IsStale(now, network_changes_);
   entry->CountHit(/* hit_is_stale= */ is_stale);
-  RecordLookup(is_stale ? LOOKUP_HIT_STALE : LOOKUP_HIT_VALID, now, entry);
 
   if (stale_out)
     entry->GetStaleness(now, network_changes_, stale_out);
@@ -246,8 +237,6 @@ void HostCache::Set(const Key& key,
   bool result_changed = false;
   auto it = entries_.find(key);
   if (it != entries_.end()) {
-    bool is_stale = it->second.IsStale(now, network_changes_);
-
     base::Optional<AddressListDeltaType> addresses_delta;
     if (entry.addresses() || it->second.addresses()) {
       if (entry.addresses() && it->second.addresses()) {
@@ -297,8 +286,6 @@ void HostCache::Set(const Key& key,
           std::max(addresses_delta.value(), nonaddress_delta.value());
     }
 
-    LogRecordSet(is_stale ? SET_UPDATE_STALE : SET_UPDATE_VALID, now,
-                 &it->second, entry, overall_delta);
     // TODO(juliatuttle): Remember some old metadata (hit count or frequency or
     // something like that) if it's useful for better eviction algorithms?
     result_changed =
@@ -309,7 +296,6 @@ void HostCache::Set(const Key& key,
     result_changed = true;
     if (size() == max_entries_)
       EvictOneEntry(now);
-    LogRecordSet(SET_INSERT, now, nullptr, entry, DELTA_DISJOINT);
   }
 
   AddEntry(Key(key), Entry(entry, now, ttl, network_changes_));
@@ -338,7 +324,6 @@ void HostCache::set_persistence_delegate(PersistenceDelegate* delegate) {
 
 void HostCache::clear() {
   DCHECK_CALLED_ON_VALID_THREAD(thread_checker_);
-  RecordEraseAll(ERASE_CLEAR, tick_clock_->NowTicks());
 
   // Don't bother scheduling a write if there's nothing to clear.
   if (size() == 0)
@@ -359,12 +344,10 @@ void HostCache::ClearForHosts(
   }
 
   bool changed = false;
-  base::TimeTicks now = tick_clock_->NowTicks();
   for (auto it = entries_.begin(); it != entries_.end();) {
     auto next_it = std::next(it);
 
     if (host_filter.Run(it->first.hostname)) {
-      RecordErase(ERASE_CLEAR, now, it->second);
       entries_.erase(it);
       changed = true;
     }
@@ -607,110 +590,9 @@ void HostCache::EvictOneEntry(base::TimeTicks now) {
     }
   }
 
-  RecordErase(ERASE_EVICT, now, oldest_it->second);
   entries_.erase(oldest_it);
 }
 
-void HostCache::LogRecordSet(SetOutcome outcome,
-                             base::TimeTicks now,
-                             const Entry* old_entry,
-                             const Entry& new_entry,
-                             AddressListDeltaType delta) {
-  CACHE_HISTOGRAM_ENUM("Set", outcome, MAX_SET_OUTCOME);
-  switch (outcome) {
-    case SET_INSERT:
-    case SET_UPDATE_VALID:
-      // Nothing to log here.
-      break;
-    case SET_UPDATE_STALE: {
-      EntryStaleness stale;
-      old_entry->GetStaleness(now, network_changes_, &stale);
-      CACHE_HISTOGRAM_TIME("UpdateStale.ExpiredBy", stale.expired_by);
-      CACHE_HISTOGRAM_COUNT("UpdateStale.NetworkChanges",
-                            stale.network_changes);
-      CACHE_HISTOGRAM_COUNT("UpdateStale.StaleHits", stale.stale_hits);
-      if (old_entry->error() == OK && new_entry.error() == OK) {
-        LogRecordUpdateStale(delta, stale);
-      }
-      break;
-    }
-    case MAX_SET_OUTCOME:
-      NOTREACHED();
-      break;
-  }
-}
-
-void HostCache::LogRecordUpdateStale(AddressListDeltaType delta,
-                                     const EntryStaleness& stale) {
-  CACHE_HISTOGRAM_ENUM("UpdateStale.AddressListDelta", delta, MAX_DELTA_TYPE);
-  switch (delta) {
-    case DELTA_IDENTICAL:
-      CACHE_HISTOGRAM_TIME("UpdateStale.ExpiredBy_Identical", stale.expired_by);
-      CACHE_HISTOGRAM_COUNT("UpdateStale.NetworkChanges_Identical",
-                            stale.network_changes);
-      break;
-    case DELTA_REORDERED:
-      CACHE_HISTOGRAM_TIME("UpdateStale.ExpiredBy_Reordered", stale.expired_by);
-      CACHE_HISTOGRAM_COUNT("UpdateStale.NetworkChanges_Reordered",
-                            stale.network_changes);
-      break;
-    case DELTA_OVERLAP:
-      CACHE_HISTOGRAM_TIME("UpdateStale.ExpiredBy_Overlap", stale.expired_by);
-      CACHE_HISTOGRAM_COUNT("UpdateStale.NetworkChanges_Overlap",
-                            stale.network_changes);
-      break;
-    case DELTA_DISJOINT:
-      CACHE_HISTOGRAM_TIME("UpdateStale.ExpiredBy_Disjoint", stale.expired_by);
-      CACHE_HISTOGRAM_COUNT("UpdateStale.NetworkChanges_Disjoint",
-                            stale.network_changes);
-      break;
-    case MAX_DELTA_TYPE:
-      NOTREACHED();
-      break;
-  }
-}
-
-void HostCache::RecordLookup(LookupOutcome outcome,
-                             base::TimeTicks now,
-                             const Entry* entry) {
-  CACHE_HISTOGRAM_ENUM("Lookup", outcome, MAX_LOOKUP_OUTCOME);
-  switch (outcome) {
-    case LOOKUP_MISS_ABSENT:
-    case LOOKUP_MISS_STALE:
-    case LOOKUP_HIT_VALID:
-      // Nothing to log here.
-      break;
-    case LOOKUP_HIT_STALE:
-      CACHE_HISTOGRAM_TIME("LookupStale.ExpiredBy", now - entry->expires());
-      CACHE_HISTOGRAM_COUNT("LookupStale.NetworkChanges",
-                            network_changes_ - entry->network_changes());
-      break;
-    case MAX_LOOKUP_OUTCOME:
-      NOTREACHED();
-      break;
-  }
-}
-
-void HostCache::RecordErase(EraseReason reason,
-                            base::TimeTicks now,
-                            const Entry& entry) {
-  HostCache::EntryStaleness stale;
-  entry.GetStaleness(now, network_changes_, &stale);
-  CACHE_HISTOGRAM_ENUM("Erase", reason, MAX_ERASE_REASON);
-  if (stale.is_stale()) {
-    CACHE_HISTOGRAM_TIME("EraseStale.ExpiredBy", stale.expired_by);
-    CACHE_HISTOGRAM_COUNT("EraseStale.NetworkChanges", stale.network_changes);
-    CACHE_HISTOGRAM_COUNT("EraseStale.StaleHits", entry.stale_hits());
-  } else {
-    CACHE_HISTOGRAM_TIME("EraseValid.ValidFor", -stale.expired_by);
-  }
-}
-
-void HostCache::RecordEraseAll(EraseReason reason, base::TimeTicks now) {
-  for (const auto& it : entries_)
-    RecordErase(reason, now, it.second);
-}
-
 bool HostCache::HasEntry(base::StringPiece hostname,
                          HostCache::Entry::Source* source_out,
                          HostCache::EntryStaleness* stale_out) {

net/dns/host_cache.h

@@ -276,19 +276,6 @@ class NET_EXPORT HostCache {
 
   Entry* LookupInternal(const Key& key);
 
-  void LogRecordSet(SetOutcome outcome,
-                    base::TimeTicks now,
-                    const Entry* old_entry,
-                    const Entry& new_entry,
-                    AddressListDeltaType delta);
-  void LogRecordUpdateStale(AddressListDeltaType delta,
-                            const EntryStaleness& stale);
-  void RecordLookup(LookupOutcome outcome,
-                    base::TimeTicks now,
-                    const Entry* entry);
-  void RecordErase(EraseReason reason, base::TimeTicks now, const Entry& entry);
-  void RecordEraseAll(EraseReason reason, base::TimeTicks now);
-
   // Returns true if this HostCache can contain no entries.
   bool caching_is_disabled() const { return max_entries_ == 0; }
 

tools/metrics/histograms/histograms.xml

@@ -21575,12 +21575,18 @@ uploading your change for review.
 </histogram>
 
 <histogram name="DNS.HostCache.Erase" enum="DNS.HostCache.EraseReason">
+  <obsolete>
+    Deprecated as of 11/2018.
+  </obsolete>
   <owner>pauljensen@chromium.org</owner>
   <owner>mef@chromium.org</owner>
   <summary>The reason for erasing a DNS entry from the host cache.</summary>
 </histogram>
 
 <histogram name="DNS.HostCache.EraseStale.ExpiredBy" units="ms">
+  <obsolete>
+    Deprecated as of 11/2018.
+  </obsolete>
   <owner>pauljensen@chromium.org</owner>
   <owner>mef@chromium.org</owner>
   <summary>
@@ -21590,6 +21596,9 @@ uploading your change for review.
 </histogram>
 
 <histogram name="DNS.HostCache.EraseStale.NetworkChanges" units="changes">
+  <obsolete>
+    Deprecated as of 11/2018.
+  </obsolete>
   <owner>pauljensen@chromium.org</owner>
   <owner>mef@chromium.org</owner>
   <summary>
@@ -21599,6 +21608,9 @@ uploading your change for review.
 </histogram>
 
 <histogram name="DNS.HostCache.EraseStale.StaleHits" units="hits">
+  <obsolete>
+    Deprecated as of 11/2018.
+  </obsolete>
   <owner>pauljensen@chromium.org</owner>
   <owner>mef@chromium.org</owner>
   <summary>
@@ -21608,6 +21620,9 @@ uploading your change for review.
 </histogram>
 
 <histogram name="DNS.HostCache.EraseValid.ValidFor" units="ms">
+  <obsolete>
+    Deprecated as of 11/2018.
+  </obsolete>
   <owner>pauljensen@chromium.org</owner>
   <owner>mef@chromium.org</owner>
   <summary>
@@ -21617,12 +21632,18 @@ uploading your change for review.
 </histogram>
 
 <histogram name="DNS.HostCache.Lookup" enum="DNS.HostCache.LookupOutcome">
+  <obsolete>
+    Deprecated as of 11/2018.
+  </obsolete>
   <owner>pauljensen@chromium.org</owner>
   <owner>mef@chromium.org</owner>
   <summary>The outcome of looking up a DNS entry in the host cache.</summary>
 </histogram>
 
 <histogram name="DNS.HostCache.LookupStale.ExpiredBy" units="ms">
+  <obsolete>
+    Deprecated as of 11/2018.
+  </obsolete>
   <owner>pauljensen@chromium.org</owner>
   <owner>mef@chromium.org</owner>
   <summary>
@@ -21632,6 +21653,9 @@ uploading your change for review.
 </histogram>
 
 <histogram name="DNS.HostCache.LookupStale.NetworkChanges" units="changes">
+  <obsolete>
+    Deprecated as of 11/2018.
+  </obsolete>
   <owner>pauljensen@chromium.org</owner>
   <owner>mef@chromium.org</owner>
   <summary>
@@ -21657,6 +21681,9 @@ uploading your change for review.
 </histogram>
 
 <histogram name="DNS.HostCache.Set" enum="DNS.HostCache.SetOutcome">
+  <obsolete>
+    Deprecated as of 11/2018.
+  </obsolete>
   <owner>pauljensen@chromium.org</owner>
   <owner>mef@chromium.org</owner>
   <summary>The outcome of setting a DNS entry in the host cache.</summary>
@@ -21664,6 +21691,9 @@ uploading your change for review.
 
 <histogram name="DNS.HostCache.UpdateStale.AddressListDelta"
     enum="DNS.AddressListDeltaType">
+  <obsolete>
+    Deprecated as of 11/2018.
+  </obsolete>
   <owner>pauljensen@chromium.org</owner>
   <owner>mef@chromium.org</owner>
   <summary>
@@ -21674,6 +21704,9 @@ uploading your change for review.
 </histogram>
 
 <histogram name="DNS.HostCache.UpdateStale.ExpiredBy" units="ms">
+  <obsolete>
+    Deprecated as of 11/2018.
+  </obsolete>
   <owner>pauljensen@chromium.org</owner>
   <owner>mef@chromium.org</owner>
   <summary>
@@ -21683,6 +21716,9 @@ uploading your change for review.
 </histogram>
 
 <histogram name="DNS.HostCache.UpdateStale.NetworkChanges" units="changes">
+  <obsolete>
+    Deprecated as of 11/2018.
+  </obsolete>
   <owner>pauljensen@chromium.org</owner>
   <owner>mef@chromium.org</owner>
   <summary>
@@ -21693,6 +21729,9 @@ uploading your change for review.
 </histogram>
 
 <histogram name="DNS.HostCache.UpdateStale.StaleHits" units="hits">
+  <obsolete>
+    Deprecated as of 11/2018.
+  </obsolete>
   <owner>pauljensen@chromium.org</owner>
   <owner>mef@chromium.org</owner>
   <summary>