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

net/http/disk_cache_based_quic_server_info.cc

 // Copyright 2014 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/http/disk_cache_based_quic_server_info.h"
 
 #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"
 #include "net/http/http_cache.h"
 #include "net/http/http_network_session.h"
 #include "net/quic/quic_server_id.h"
 
 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.
 //
 // Unfortunately, DiskCacheBasedQuicServerInfo may be deleted before the
 // operation completes causing a use-after-free.
 //
 // This data shim struct is meant to provide a location for the disk_cache
 // APIs to write into even if the originating DiskCacheBasedQuicServerInfo
 // object has been deleted.  The lifetime for instances of this struct
 // should be bound to the CompletionCallback that is passed to the disk_cache
@@ skipping 79 matching lines @@
 
   if (!backend_)
     return;
 
   state_ = CREATE_OR_OPEN;
   DoLoop(OK);
 }
 
 DiskCacheBasedQuicServerInfo::~DiskCacheBasedQuicServerInfo() {
   DCHECK(user_callback_.is_null());
-  if (entry_)
+  if (entry_) {
     entry_->Close();
+    RecordDiskCacheEntryState(DISK_CACHE_ENTRY_CLOSED);
+  }
 }
 
 std::string DiskCacheBasedQuicServerInfo::key() const {
   return "quicserverinfo:" + server_id_.ToString();
 }
 
 void DiskCacheBasedQuicServerInfo::OnIOComplete(CacheOperationDataShim* unused,
                                                 int rv) {
   DCHECK_NE(NONE, state_);
   rv = DoLoop(rv);
@@ skipping 60 matching lines @@
     state_ = WAIT_FOR_DATA_READY_DONE;
   }
   return OK;
 }
 
 int DiskCacheBasedQuicServerInfo::DoOpenComplete(int rv) {
   if (rv == OK) {
     entry_ = data_shim_->entry;
     state_ = READ;
     found_entry_ = true;
+    RecordDiskCacheEntryState(DISK_CACHE_ENTRY_OPENED);
   } else {
     state_ = WAIT_FOR_DATA_READY_DONE;
   }
 
   return OK;
 }
 
 int DiskCacheBasedQuicServerInfo::DoReadComplete(int rv) {
   if (rv > 0)
     data_.assign(read_buffer_->data(), rv);
 
   state_ = WAIT_FOR_DATA_READY_DONE;
   return OK;
 }
 
 int DiskCacheBasedQuicServerInfo::DoWriteComplete(int rv) {
   // Keep the entry open for future writes.
   new_data_.clear();
   state_ = NONE;
   return OK;
 }
 
 int DiskCacheBasedQuicServerInfo::DoCreateOrOpenComplete(int rv) {
   if (rv != OK) {
     state_ = SET_DONE;
   } else {
-    if (!entry_)
+    if (!entry_) {
       entry_ = data_shim_->entry;
+      RecordDiskCacheEntryState(DISK_CACHE_ENTRY_OPENED);
+    }
+    DCHECK(entry_);
     state_ = WRITE;
   }
   return OK;
 }
 
 int DiskCacheBasedQuicServerInfo::DoGetBackend() {
   state_ = GET_BACKEND_COMPLETE;
   return http_cache_->GetBackend(&data_shim_->backend, io_callback_);
 }
 
@@ skipping 39 matching lines @@
 
   return backend_->CreateEntry(key(), &data_shim_->entry, io_callback_);
 }
 
 int DiskCacheBasedQuicServerInfo::DoWaitForDataReadyDone() {
   DCHECK(!ready_);
   state_ = NONE;
   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;
   return OK;
 }
 
 }  // namespace net