Index: net/http/http_cache_writers.h |
diff --git a/net/http/http_cache_writers.h b/net/http/http_cache_writers.h |
new file mode 100644 |
index 0000000000000000000000000000000000000000..8c2403fef37419c407b045ab6d564234769fed6b |
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+++ b/net/http/http_cache_writers.h |
@@ -0,0 +1,222 @@ |
+// Copyright (c) 2017 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. |
+ |
+#ifndef NET_HTTP_HTTP_CACHE_WRITERS_H_ |
+#define NET_HTTP_HTTP_CACHE_WRITERS_H_ |
+#include <list> |
+#include <memory> |
+#include "base/memory/weak_ptr.h" |
+#include "net/base/completion_callback.h" |
+#include "net/http/http_cache.h" |
+ |
+// If multiple HttpCache::Transactions are accessing the same cache entry |
+// simultaneously, their access to the data read from network is synchronized |
+// by HttpCache::Writers. This enables each of those transactions to drive |
+// reading the response body from the network ensuring a slow consumer does not |
+// starve other consumers of the same resource. |
+ |
+namespace net { |
+ |
+// Writer represents the set of all HttpCache::Transactions that are |
+// reading from the network using the same network transaction and writing to |
+// the same cache entry. It is owned by the ActiveEntry. |
+class NET_EXPORT_PRIVATE HttpCache::Writers { |
+ public: |
+ // |*entry| and |*cache| should always be valid when accessed from Writers. |
+ Writers(HttpCache* cache, ActiveEntry* entry); |
+ ~Writers(); |
+ |
+ // Invokes Read on network transaction if a read is not already in progress. |
+ // In case a read is already in progress then this transaction is added to |
+ // a waiting queue and ERR_IO_PENDING is returned. If ERR_IO_PENDING is |
+ // returned, the result of the read will be later communicated to the consumer |
+ // via the |callback|. |
+ int Read(scoped_refptr<IOBuffer> buf, |
+ int buf_len, |
+ const CompletionCallback& callback, |
+ Transaction* transaction); |
+ |
+ // Invoked when StopCaching is called on a member transaction. |
+ // It stops caching only if there are no other transactions. Returns true if |
+ // caching can be stopped. |
+ bool StopCaching(Transaction* transaction); |
+ |
+ // Membership functions. |
+ |
+ // Adds an HttpCache::Transaction to Writers and if its the first transaction |
+ // added, transfers the ownership of the network transaction to Writers. |
+ // Should only be invoked if CanAddTransaction() returns true. If |
+ // |network_transaction| is non-null, it will be assigned to |
+ // |network_transaction_|. The first transaction added should definitely pass |
+ // a non-null |network_transaction|. |transaction| can be destroyed at any |
+ // point and it should invoke RemoveTransaction() during its destruction. |
+ void AddTransaction(Transaction* transaction, |
+ std::unique_ptr<HttpTransaction> network_transaction); |
+ |
+ // Removes a transaction. |
+ void RemoveTransaction(Transaction* transaction); |
+ |
+ // Removes all transactions. |
+ void RemoveAllTransactions(); |
+ |
+ // Invoked when there is a change in a member transaction's priority or a |
+ // member transaction is removed. |
+ void PriorityChanged(); |
+ |
+ // Returns true if this object is empty. |
+ bool IsEmpty() const { return all_writers_.empty(); } |
+ |
+ // Returns true is |transaction| is part of writers. |
+ bool IsPresent(Transaction* transaction) const { |
+ return all_writers_.count(transaction) > 0; |
+ } |
+ |
+ // When response is completely written, any idle writers are moved to |
+ // entry_->readers. |
+ void MoveIdleWritersToReaders(); |
+ |
+ // Makes writing an exclusine operation implying that Writers can contain at |
+ // most one transaction for the complete reading/writing of the response body. |
+ void SetExclusive() { is_exclusive_ = true; } |
Randy Smith (Not in Mondays)
2017/05/18 01:02:56
What happens if this is called with a lot of trans
Randy Smith (Not in Mondays)
2017/05/22 01:56:55
Ping?
shivanisha
2017/05/31 19:21:26
Added a dcheck that only 0 or 1 transactions shoul
Randy Smith (Not in Mondays)
2017/06/06 12:54:57
SG. Just so I'm tracking, what's the use case for
shivanisha
2017/06/07 15:19:18
Actually, adding an is_exclusive argument to AddTr
|
+ |
+ // Returns true if more writers can be added for shared writing. |
+ bool CanAddWriters() const; |
+ |
+ HttpTransaction* network_transaction() { return network_transaction_.get(); } |
+ |
+ // Invoked from HttpCache when it is notified of a transaction failing to |
+ // write. |error| indicates network read error code or cache write error. |
+ void ProcessFailure(Transaction* transaction, int error); |
+ |
+ // Invoked to mark an entry as truncated. Should be invoked when reading is |
+ // not currently in progress. |
+ void TruncateEntry(); |
+ |
+ LoadState GetWriterLoadState(); |
+ |
+ // For testing. |
+ |
+ int CountTransactionsForTesting() const { return all_writers_.size(); } |
+ bool IsTruncatedForTesting() const { return truncated_; } |
+ |
+ private: |
+ enum class State { |
+ NONE, |
+ NETWORK_READ, |
+ NETWORK_READ_COMPLETE, |
+ CACHE_WRITE_DATA, |
+ CACHE_WRITE_DATA_COMPLETE, |
+ CACHE_WRITE_TRUNCATED_RESPONSE, |
+ CACHE_WRITE_TRUNCATED_RESPONSE_COMPLETE, |
+ }; |
+ |
+ // These transactions are waiting on Read. After the active transaction |
+ // completes writing the data to the cache, their buffer would be filled with |
+ // the data and their callback will be invoked. |
+ struct WaitingForRead { |
+ Transaction* transaction; |
+ scoped_refptr<IOBuffer> read_buf; |
+ int read_buf_len; |
+ int write_len; |
+ const CompletionCallback callback; |
+ WaitingForRead(Transaction* transaction, |
+ scoped_refptr<IOBuffer> read_buf, |
+ int len, |
+ const CompletionCallback& consumer_callback); |
+ ~WaitingForRead(); |
+ WaitingForRead(const WaitingForRead&); |
+ }; |
+ using WaitingForReadList = std::list<WaitingForRead>; |
+ |
+ // Runs the state transition loop. Resets and calls |callback_| on exit, |
+ // unless the return value is ERR_IO_PENDING. |
+ int DoLoop(int result); |
+ |
+ // State machine functions. |
+ int DoNetworkRead(); |
+ int DoNetworkReadComplete(int result); |
+ int DoCacheWriteData(int num_bytes); |
+ int DoCacheWriteDataComplete(int result); |
+ int DoCacheWriteTruncatedResponse(); |
+ int DoCacheWriteTruncatedResponseComplete(int result); |
+ |
+ // Helper functions for callback. |
+ |
+ void OnNetworkReadFailure(int result); |
+ void OnCacheWriteFailure(); |
+ void OnDataReceived(int result); |
+ |
+ // Helper function for writing to cache. |
+ int WriteToEntry(int index, |
+ int offset, |
+ IOBuffer* data, |
+ int data_len, |
+ const CompletionCallback& callback); |
+ |
+ // Notifies the transactions waiting on Read of the result, by posting a task |
+ // for each of them. |
+ void ProcessWaitingForReadTransactions(int result); |
+ |
+ // Sets the state of idle writers so that they can fail any subsequent |
+ // Read. |
+ void SetIdleWritersFailState(int result); |
+ |
+ RequestPriority GetCurrentHighestPriority(); |
+ |
+ bool IsResponseCompleted(); |
+ |
+ int WriteResponseInfo(bool truncated); |
+ |
+ // IO Completion callback function. |
+ void OnIOComplete(int result); |
+ |
+ State next_state_ = State::NONE; |
+ |
+ // True if only reading from network and not writing to cache. |
+ bool network_read_only_ = false; |
+ |
+ // Http Cache. |
+ HttpCache* cache_; |
+ |
+ // Owner of this object. |
+ ActiveEntry* entry_ = nullptr; |
Randy Smith (Not in Mondays)
2017/05/18 01:02:55
My understanding is that Chromium prefers to keep
Randy Smith (Not in Mondays)
2017/05/22 01:56:56
Ping?
shivanisha
2017/05/31 19:21:26
Changed the header file such that all fields are i
|
+ |
+ std::unique_ptr<HttpTransaction> network_transaction_; |
+ |
+ scoped_refptr<IOBuffer> read_buf_; |
+ |
+ int io_buf_len_ = 0; |
+ int write_len_ = 0; |
+ |
+ // The cache transaction that is the current consumer of network_transaction_ |
+ // ::Read or writing to the entry and is waiting for the operation to be |
+ // completed. This is used to ensure there is at most one consumer of |
+ // network_transaction_ at a time. |
+ Transaction* active_transaction_ = nullptr; |
+ |
+ // Transactions whose consumers have invoked Read, but another transaction is |
+ // currently the |active_transaction_|. After the network read and cache write |
+ // is complete, the waiting transactions will be notified. |
+ WaitingForReadList waiting_for_read_; |
+ |
+ // Includes all transactions. |
+ TransactionSet all_writers_; |
+ |
+ // True if multiple transactions are not allowed e.g. for partial requests. |
+ bool is_exclusive_ = false; |
+ |
+ // Current priority of the request. If a higher priority transaction is |
+ // added, the priority of network transaction will be increased. |
+ RequestPriority priority_ = MINIMUM_PRIORITY; |
+ |
+ bool truncated_ = false; // used for testing. |
+ |
+ CompletionCallback callback_; // Consumer's callback. |
Randy Smith (Not in Mondays)
2017/05/18 01:02:55
Suggestion: Change comment to "Callback for active
Randy Smith (Not in Mondays)
2017/05/22 01:56:56
Ping?
shivanisha
2017/05/31 19:21:26
done
|
+ CompletionCallback io_callback_; |
Randy Smith (Not in Mondays)
2017/05/18 01:02:56
Suggestion: In my ideal world this would be const,
Randy Smith (Not in Mondays)
2017/05/22 01:56:56
Ping?
shivanisha
2017/05/31 19:21:26
It seems nothing should come after WeakPtrFactory
Randy Smith (Not in Mondays)
2017/06/06 12:54:57
If you're doing the initialization at the call sit
shivanisha
2017/06/07 15:19:18
Removed the member variable.
|
+ base::WeakPtrFactory<Writers> weak_factory_; |
+ DISALLOW_COPY_AND_ASSIGN(Writers); |
+}; |
+ |
+} // namespace net |
+#endif // NET_HTTP_HTTP_CACHE_WRITERS_H_ |