HttpCache::Transaction layer allowing parallel validation

net/http/http_cache_transaction.h

 // 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.
 
 // This file declares HttpCache::Transaction, a private class of HttpCache so
 // it should only be included by http_cache.cc
 
 #ifndef NET_HTTP_HTTP_CACHE_TRANSACTION_H_
 #define NET_HTTP_HTTP_CACHE_TRANSACTION_H_
 
@@ skipping 145 matching lines @@
   void PopulateNetErrorDetails(NetErrorDetails* details) const override;
   void SetPriority(RequestPriority priority) override;
   void SetWebSocketHandshakeStreamCreateHelper(
       WebSocketHandshakeStreamBase::CreateHelper* create_helper) override;
   void SetBeforeNetworkStartCallback(
       const BeforeNetworkStartCallback& callback) override;
   void SetBeforeHeadersSentCallback(
       const BeforeHeadersSentCallback& callback) override;
   int ResumeNetworkStart() override;
   void GetConnectionAttempts(ConnectionAttempts* out) const override;
+  void SetValidatingCannotProceed();

[jkarlin, 2017/03/23 18:37:38]

This isn't an HttpTransaction method (as the above are). Should have a newline
above. Also, needs a comment since it's a public non-override method.

[shivanisha, 2017/03/29 03:39:29]

Done.

 
   // Returns the estimate of dynamically allocated memory in bytes.
   size_t EstimateMemoryUsage() const;
 
  private:
   static const size_t kNumValidationHeaders = 2;
   // Helper struct to pair a header name with its value, for
   // headers used to validate cache entries.
   struct ValidationHeaders {
     ValidationHeaders() : initialized(false) {}
@@ skipping 37 matching lines @@
     STATE_OVERWRITE_CACHED_RESPONSE,
     STATE_CACHE_WRITE_RESPONSE,
     STATE_CACHE_WRITE_RESPONSE_COMPLETE,
     STATE_TRUNCATE_CACHED_DATA,
     STATE_TRUNCATE_CACHED_DATA_COMPLETE,
     STATE_TRUNCATE_CACHED_METADATA,
     STATE_TRUNCATE_CACHED_METADATA_COMPLETE,
     STATE_PARTIAL_HEADERS_RECEIVED,
     STATE_CACHE_READ_METADATA,
     STATE_CACHE_READ_METADATA_COMPLETE,
+    STATE_WAIT_BEFORE_READ,
+    STATE_WAIT_BEFORE_READ_COMPLETE,
 
     // These states are entered from Read/AddTruncatedFlag.
     STATE_NETWORK_READ,
     STATE_NETWORK_READ_COMPLETE,
     STATE_CACHE_READ_DATA,
     STATE_CACHE_READ_DATA_COMPLETE,
     STATE_CACHE_WRITE_DATA,
     STATE_CACHE_WRITE_DATA_COMPLETE,
     STATE_CACHE_WRITE_TRUNCATED_RESPONSE,
     STATE_CACHE_WRITE_TRUNCATED_RESPONSE_COMPLETE
   };
 
   // Used for categorizing validation triggers in histograms.
   // NOTE: This enumeration is used in histograms, so please do not add entries
   // in the middle.
   enum ValidationCause {
     VALIDATION_CAUSE_UNDEFINED,
     VALIDATION_CAUSE_VARY_MISMATCH,
     VALIDATION_CAUSE_VALIDATE_FLAG,
     VALIDATION_CAUSE_STALE,
     VALIDATION_CAUSE_ZERO_FRESHNESS,
     VALIDATION_CAUSE_MAX
   };
 
   // Runs the state transition loop. Resets and calls |callback_| on exit,
   // unless the return value is ERR_IO_PENDING.
   int DoLoop(int result);
+  int DoLoopImpl(int result);
 
   // Each of these methods corresponds to a State value.  If there is an
   // argument, the value corresponds to the return of the previous state or
   // corresponding callback.
   int DoGetBackend();
   int DoGetBackendComplete(int result);
   int DoInitEntry();
   int DoOpenEntry();
   int DoOpenEntryComplete(int result);
   int DoDoomEntry();
@@ skipping 19 matching lines @@
   int DoCacheWriteUpdatedResponseComplete(int result);
   int DoUpdateCachedResponseComplete(int result);
   int DoOverwriteCachedResponse();
   int DoCacheWriteResponse();
   int DoCacheWriteResponseComplete(int result);
   int DoTruncateCachedData();
   int DoTruncateCachedDataComplete(int result);
   int DoTruncateCachedMetadata();
   int DoTruncateCachedMetadataComplete(int result);
   int DoPartialHeadersReceived();
+  int DoWaitBeforeRead();
+  int DoWaitBeforeReadComplete(int result);
   int DoCacheReadMetadata();
   int DoCacheReadMetadataComplete(int result);
   int DoNetworkRead();
   int DoNetworkReadComplete(int result);
   int DoCacheReadData();
   int DoCacheReadDataComplete(int result);
   int DoCacheWriteData(int num_bytes);
   int DoCacheWriteDataComplete(int result);
   int DoCacheWriteTruncatedResponse();
   int DoCacheWriteTruncatedResponseComplete(int result);
@@ skipping 108 matching lines @@
   int DoRestartPartialRequest();
 
   // Resets the relavant internal state to remove traces of internal processing
   // related to range requests. Deletes |partial_| if |delete_object| is true.
   void ResetPartialState(bool delete_object);
 
   // Resets |network_trans_|, which must be non-NULL.  Also updates
   // |old_network_trans_load_timing_|, which must be NULL when this is called.
   void ResetNetworkTransaction();
 
+  // Since a transaction could be doing validation of request headers in
+  // parallel with another request writing response data to the entry, failure
+  // to write the data might lead to restarting this request. This function
+  // resets all the required variables to be able to restart the transaction's
+  // state machine.
+  void RestartAfterValidationStarted();
+
   // Returns true if we should bother attempting to resume this request if it is
   // aborted while in progress. If |has_data| is true, the size of the stored
   // data is considered for the result.
   bool CanResume(bool has_data);
 
   // Setter for response_ and auth_response_. It updates its cache entry status,
   // if needed.
   void SetResponse(const HttpResponseInfo& new_response);
   void SetAuthResponse(const HttpResponseInfo& new_response);
 
@@ skipping 16 matching lines @@
   RequestPriority priority_;
   NetLogWithSource net_log_;
   std::unique_ptr<HttpRequestInfo> custom_request_;
   HttpRequestHeaders request_headers_copy_;
   // If extra_headers specified a "if-modified-since" or "if-none-match",
   // |external_validation_| contains the value of those headers.
   ValidationHeaders external_validation_;
   base::WeakPtr<HttpCache> cache_;
   HttpCache::ActiveEntry* entry_;
   HttpCache::ActiveEntry* new_entry_;
+  bool created_entry_;
   std::unique_ptr<HttpTransaction> network_trans_;
   CompletionCallback callback_;  // Consumer's callback.
   HttpResponseInfo response_;
   HttpResponseInfo auth_response_;
   const HttpResponseInfo* new_response_;
   std::string cache_key_;
   Mode mode_;
+  Mode original_mode_;  // Used when restarting the transaction.
   bool reading_;  // We are already reading. Never reverts to false once set.
   bool invalid_range_;  // We may bypass the cache for this request.
   bool truncated_;  // We don't have all the response data.
   bool is_sparse_;  // The data is stored in sparse byte ranges.
   bool range_requested_;  // The user requested a byte range.
   bool handling_206_;  // We must deal with this 206 response.
   bool cache_pending_;  // We are waiting for the HttpCache.
   bool done_reading_;  // All available data was read.
   bool vary_mismatch_;  // The request doesn't match the stored vary data.
   bool couldnt_conditionalize_request_;
   bool bypass_lock_for_test_;  // A test is exercising the cache lock.
   bool fail_conditionalization_for_test_;  // Fail ConditionalizeRequest.
+  bool validating_cannot_proceed_;
   scoped_refptr<IOBuffer> read_buf_;
   int io_buf_len_;
   int read_offset_;
   int effective_load_flags_;
   int write_len_;
   std::unique_ptr<PartialData> partial_;  // We are dealing with range requests.
   CompletionCallback io_callback_;
 
   // Members used to track data for histograms.
   // This cache_entry_status_ takes precedence over
@@ skipping 34 matching lines @@
   bool in_do_loop_;
 
   base::WeakPtrFactory<Transaction> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(Transaction);
 };
 
 }  // namespace net
 
 #endif  // NET_HTTP_HTTP_CACHE_TRANSACTION_H_