QUIC - track the open and close states of disk cache entries of

QuicServerInfo.

BUG=417835
R=rch@chromium.org, asvitkine@chromium.org

Review URL: https://codereview.chromium.org/618083003

Cr-Commit-Position: refs/heads/master@{#297776}

net/http/disk_cache_based_quic_server_info.cc

@@ -7,6 +7,7 @@
 #include "base/bind.h"
 #include "base/callback.h"
 #include "base/logging.h"
+#include "base/metrics/histogram.h"
 #include "net/base/completion_callback.h"
 #include "net/base/io_buffer.h"
 #include "net/base/net_errors.h"
@@ -16,6 +17,18 @@
 
 namespace net {
 
+// Histogram for tracking down the state of disk_cache::Entry.
+enum DiskCacheEntryState {
+  DISK_CACHE_ENTRY_OPENED = 0,
+  DISK_CACHE_ENTRY_CLOSED = 1,
+  DISK_CACHE_ENTRY_NUM_STATES = 2,
+};
+
+void RecordDiskCacheEntryState(DiskCacheEntryState entry_state) {
+  UMA_HISTOGRAM_ENUMERATION("Net.QuicDiskCache.EntryState", entry_state,
+                            DISK_CACHE_ENTRY_NUM_STATES);
+}
+
 // Some APIs inside disk_cache take a handle that the caller must keep alive
 // until the API has finished its asynchronous execution.
 //
@@ -119,8 +132,10 @@ void DiskCacheBasedQuicServerInfo::Persist() {
 
 DiskCacheBasedQuicServerInfo::~DiskCacheBasedQuicServerInfo() {
   DCHECK(user_callback_.is_null());
-  if (entry_)
+  if (entry_) {
     entry_->Close();
+    RecordDiskCacheEntryState(DISK_CACHE_ENTRY_CLOSED);
+  }
 }
 
 std::string DiskCacheBasedQuicServerInfo::key() const {
@@ -201,6 +216,7 @@ int DiskCacheBasedQuicServerInfo::DoOpenComplete(int rv) {
     entry_ = data_shim_->entry;
     state_ = READ;
     found_entry_ = true;
+    RecordDiskCacheEntryState(DISK_CACHE_ENTRY_OPENED);
   } else {
     state_ = WAIT_FOR_DATA_READY_DONE;
   }
@@ -228,6 +244,7 @@ int DiskCacheBasedQuicServerInfo::DoCreateOrOpenComplete(int rv) {
     if (!entry_) {
       entry_ = data_shim_->entry;
       found_entry_ = true;
+      RecordDiskCacheEntryState(DISK_CACHE_ENTRY_OPENED);
     }
     DCHECK(entry_);
     state_ = WRITE;
@@ -289,16 +306,20 @@ int DiskCacheBasedQuicServerInfo::DoWaitForDataReadyDone() {
   ready_ = true;
   // We close the entry because, if we shutdown before ::Persist is called,
   // then we might leak a cache reference, which causes a DCHECK on shutdown.
-  if (entry_)
+  if (entry_) {
     entry_->Close();
+    RecordDiskCacheEntryState(DISK_CACHE_ENTRY_CLOSED);
+  }
   entry_ = NULL;
   Parse(data_);
   return OK;
 }
 
 int DiskCacheBasedQuicServerInfo::DoSetDone() {
-  if (entry_)
+  if (entry_) {
     entry_->Close();
+    RecordDiskCacheEntryState(DISK_CACHE_ENTRY_CLOSED);
+  }
   entry_ = NULL;
   new_data_.clear();
   state_ = NONE;

tools/metrics/histograms/histograms.xml

@@ -16836,6 +16836,14 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="Net.QuicDiskCache.EntryState" enum="QuicDiskCacheEntryState">
+  <owner>rtenneti@chromium.org</owner>
+  <summary>
+    Tracks the opening and closing of disk cache entries. Recorded each time a
+    disk cache entry is either opened or closed.
+  </summary>
+</histogram>
+
 <histogram name="Net.QuicEphemeralPortsSuggested">
   <owner>rch@chromium.org</owner>
   <summary>The number of ports suggested per server.</summary>
@@ -49711,6 +49719,11 @@ To add a new entry, add it with any value and run test to compute valid value.
   <int value="7" label="Address and port match: IPv6 IPv6"/>
 </enum>
 
+<enum name="QuicDiskCacheEntryState" type="int">
+  <int value="0" label="Opened"/>
+  <int value="1" label="Closed"/>
+</enum>
+
 <enum name="QuicErrorCodes" type="int">
   <int value="0" label="NO_ERROR"/>
   <int value="1" label="INTERNAL_ERROR"/>