Doom and create new entry when validation is not a match

net/http/http_cache_transaction.cc

 // Copyright (c) 2012 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/http_cache_transaction.h"
 
 #include "build/build_config.h"  // For OS_POSIX
 
 #if defined(OS_POSIX)
 #include <unistd.h>
@@ skipping 147 matching lines @@
       new_response_(NULL),
       mode_(NONE),
       reading_(false),
       invalid_range_(false),
       truncated_(false),
       is_sparse_(false),
       range_requested_(false),
       handling_206_(false),
       cache_pending_(false),
       done_reading_(false),
+      done_headers_create_new_entry_(false),
       vary_mismatch_(false),
       couldnt_conditionalize_request_(false),
       bypass_lock_for_test_(false),
       bypass_lock_after_headers_for_test_(false),
       fail_conditionalization_for_test_(false),
       io_buf_len_(0),
       read_offset_(0),
       effective_load_flags_(0),
       write_len_(0),
       cache_entry_status_(CacheEntryStatus::ENTRY_UNDEFINED),
@@ skipping 575 matching lines @@
       case STATE_CREATE_ENTRY_COMPLETE:
         rv = DoCreateEntryComplete(rv);
         break;
       case STATE_ADD_TO_ENTRY:
         DCHECK_EQ(OK, rv);
         rv = DoAddToEntry();
         break;
       case STATE_ADD_TO_ENTRY_COMPLETE:
         rv = DoAddToEntryComplete(rv);
         break;
+      case STATE_DONE_HEADERS_ADD_TO_ENTRY_COMPLETE:
+        rv = DoDoneHeadersAddToEntryComplete(rv);
+        break;
       case STATE_CACHE_READ_RESPONSE:
         DCHECK_EQ(OK, rv);
         rv = DoCacheReadResponse();
         break;
       case STATE_CACHE_READ_RESPONSE_COMPLETE:
         rv = DoCacheReadResponseComplete(rv);
         break;
       case STATE_TOGGLE_UNUSED_SINCE_PREFETCH:
         DCHECK_EQ(OK, rv);
         rv = DoCacheToggleUnusedSincePrefetch();
@@ skipping 339 matching lines @@
     case ERR_CACHE_RACE:
       TransitionToState(STATE_HEADERS_PHASE_CANNOT_PROCEED);
       break;
 
     default:
       // We have a race here: Maybe we failed to open the entry and decided to
       // create one, but by the time we called create, another transaction
       // already created the entry. If we want to eliminate this issue, we
       // need an atomic OpenOrCreate() method exposed by the disk cache.
       DLOG(WARNING) << "Unable to create cache entry";
+
+      // Set the mode to NONE in order to bypass the cache entry and read from
+      // the network directly.
       mode_ = NONE;
-      if (partial_)
-        partial_->RestoreHeaders(&custom_request_->extra_headers);
-      TransitionToState(STATE_SEND_REQUEST);
+      if (!done_headers_create_new_entry_) {
+        if (partial_)
+          partial_->RestoreHeaders(&custom_request_->extra_headers);
+        TransitionToState(STATE_SEND_REQUEST);
+        return OK;
+      }
+      // The headers have already been received as a result of validation,
+      // triggering the doom of the old entry.  So no network request needs to
+      // be sent. Note that since mode_ is NONE, the response won't be written
+      // to cache. Transition to STATE_CACHE_WRITE_RESPONSE as that's the state
+      // the transaction left off on when it tried to create the new entry.
+      done_headers_create_new_entry_ = false;
+      TransitionToState(STATE_CACHE_WRITE_RESPONSE);
   }
   return OK;
 }
 
 int HttpCache::Transaction::DoAddToEntry() {
   TRACE_EVENT0("io", "HttpCacheTransaction::DoAddToEntry");
   DCHECK(new_entry_);
   cache_pending_ = true;
-  TransitionToState(STATE_ADD_TO_ENTRY_COMPLETE);
   net_log_.BeginEvent(NetLogEventType::HTTP_CACHE_ADD_TO_ENTRY);
   DCHECK(entry_lock_waiting_since_.is_null());
+  int rv = cache_->AddTransactionToEntry(new_entry_, this);
+  DCHECK_EQ(rv, ERR_IO_PENDING);
+
+  // If headers phase is already done then we are here because of validation not
+  // matching and creating a new entry. This transaction should be the
+  // first transaction of that new entry and thus it should not be subject
+  // to any cache lock delays, thus returning early from here.
+  if (done_headers_create_new_entry_) {
+    DCHECK_EQ(mode_, WRITE);
+    TransitionToState(STATE_DONE_HEADERS_ADD_TO_ENTRY_COMPLETE);
+    return rv;
+  }
+
+  TransitionToState(STATE_ADD_TO_ENTRY_COMPLETE);
+
   entry_lock_waiting_since_ = TimeTicks::Now();
-  int rv = cache_->AddTransactionToEntry(new_entry_, this);
-  if (rv == ERR_IO_PENDING)
-    AddCacheLockTimeoutHandler(new_entry_);
+  AddCacheLockTimeoutHandler(new_entry_);
   return rv;
 }
 
 void HttpCache::Transaction::AddCacheLockTimeoutHandler(ActiveEntry* entry) {
   DCHECK(next_state_ == STATE_ADD_TO_ENTRY_COMPLETE ||
          next_state_ == STATE_FINISH_HEADERS_COMPLETE);
   if ((bypass_lock_for_test_ && next_state_ == STATE_ADD_TO_ENTRY_COMPLETE) ||
       (bypass_lock_after_headers_for_test_ &&
        next_state_ == STATE_FINISH_HEADERS_COMPLETE)) {
     base::ThreadTaskRunnerHandle::Get()->PostTask(
         FROM_HERE,
         base::Bind(&HttpCache::Transaction::OnCacheLockTimeout,
                    weak_factory_.GetWeakPtr(), entry_lock_waiting_since_));
   } else {
     int timeout_milliseconds = 20 * 1000;
     if (partial_ && entry->writer && entry->writer->range_requested_) {
-      // Quickly timeout and bypass the cache if we're a range request and
       // we're blocked by the reader/writer lock. Doing so eliminates a long
       // running issue, http://crbug.com/31014, where two of the same media
       // resources could not be played back simultaneously due to one locking
       // the cache entry until the entire video was downloaded.
       //
       // Bypassing the cache is not ideal, as we are now ignoring the cache
       // entirely for all range requests to a resource beyond the first. This
       // is however a much more succinct solution than the alternatives, which
       // would require somewhat significant changes to the http caching logic.
       //
@@ skipping 67 matching lines @@
       partial_->RestoreHeaders(&custom_request_->extra_headers);
     TransitionToState(STATE_SEND_REQUEST);
   } else {
     // We have to read the headers from the cached entry.
     DCHECK(mode_ & READ_META);
     TransitionToState(STATE_CACHE_READ_RESPONSE);
   }
   return OK;
 }
 
+int HttpCache::Transaction::DoDoneHeadersAddToEntryComplete(int result) {
+  // This transaction's response headers did not match its ActiveEntry so it
+  // created a new ActiveEntry (new_entry_) to write to (and doomed the old
+  // one). Now that the new entry has been created, start writing the response.
+
+  DCHECK_EQ(result, OK);
+  DCHECK_EQ(mode_, WRITE);
+  DCHECK(new_entry_);
+  DCHECK(response_.headers);
+
+  cache_pending_ = false;
+  entry_ = new_entry_;
+  done_headers_create_new_entry_ = false;
+  DCHECK_NE(response_.headers->response_code(), 304);
+  DCHECK(cache_->CanTransactionWriteResponseHeaders(
+      entry_, this, partial_ != nullptr, false));
+  TransitionToState(STATE_CACHE_WRITE_RESPONSE);
+  return OK;
+}
+
 int HttpCache::Transaction::DoCacheReadResponse() {
   TRACE_EVENT0("io", "HttpCacheTransaction::DoCacheReadResponse");
   DCHECK(entry_);
   TransitionToState(STATE_CACHE_READ_RESPONSE_COMPLETE);
 
   io_buf_len_ = entry_->disk_entry->GetDataSize(kResponseInfoIndex);
   read_buf_ = new IOBuffer(io_buf_len_);
 
   net_log_.BeginEvent(NetLogEventType::HTTP_CACHE_READ_INFO);
   return entry_->disk_entry->ReadData(kResponseInfoIndex, 0, read_buf_.get(),
@@ skipping 465 matching lines @@
     TransitionToState(STATE_PARTIAL_HEADERS_RECEIVED);
     return OK;
   }
 
   TransitionToState(STATE_CACHE_WRITE_RESPONSE);
   return OK;
 }
 
 int HttpCache::Transaction::DoCacheWriteResponse() {
   TRACE_EVENT0("io", "HttpCacheTransaction::DoCacheWriteResponse");
-  TransitionToState(STATE_CACHE_WRITE_RESPONSE_COMPLETE);
 
   // Invalidate any current entry with a successful response if this transaction
   // cannot write to this entry. This transaction then continues to read from
   // the network without writing to the backend.
   bool is_match = response_.headers->response_code() == 304;
   if (entry_ && response_.headers &&
       !cache_->CanTransactionWriteResponseHeaders(
           entry_, this, partial_ != nullptr, is_match)) {
-    cache_->DoneWritingToEntry(entry_, false, this);
+    done_headers_create_new_entry_ = true;
+
+    // The transaction needs to overwrite this response. Doom the current entry,
+    // create a new one (by going to STATE_INIT_ENTRY), and then jump straight
+    // to writing out the response, bypassing the headers checks. The mode_ is
+    // set to WRITE in order to doom any other existing entries that might exist
+    // so that this transaction can go straight to writing a response.
+    mode_ = WRITE;
+    TransitionToState(STATE_INIT_ENTRY);
+    cache_->DoomEntryValidationNoMatch(entry_);
     entry_ = nullptr;
-    mode_ = NONE;
     return OK;
   }
 
+  TransitionToState(STATE_CACHE_WRITE_RESPONSE_COMPLETE);
   return WriteResponseInfoToEntry(truncated_);
 }
 
 int HttpCache::Transaction::DoCacheWriteResponseComplete(int result) {
   TRACE_EVENT0("io", "HttpCacheTransaction::DoCacheWriteResponseComplete");
   TransitionToState(STATE_TRUNCATE_CACHED_DATA);
   return OnWriteResponseInfoToEntryComplete(result);
 }
 
 int HttpCache::Transaction::DoTruncateCachedData() {
@@ skipping 1408 matching lines @@
 }
 
 void HttpCache::Transaction::TransitionToState(State state) {
   // Ensure that the state is only set once per Do* state.
   DCHECK(in_do_loop_);
   DCHECK_EQ(STATE_UNSET, next_state_) << "Next state is " << state;
   next_state_ = state;
 }
 
 }  // namespace net