LoadTiming implementation in net, part 1.

net/base/load_timing_info.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.
+
+#ifndef NET_BASE_LOAD_TIMING_INFO_H_
+#define NET_BASE_LOAD_TIMING_INFO_H_
+
+#include "base/basictypes.h"
+#include "base/time.h"
+#include "net/base/net_export.h"
+
+namespace net {
+
+// All events that do not apply to a request have null times.  For non-HTTP
+// requests, all times other than the request_start times are null.
+//
+// The general order for events is:
+// request_start
+// proxy_start
+// proxy_end
+// *dns_start
+// *dns_end
+// *connect_start
+// *ssl_start
+// *ssl_end
+// *connect_end
+// send_start
+// send_end
+// receive_headers_end
+//
+// Those times without an asterisk are computed by the URLRequest, or by objects
+// it directly creates and always owns.  Those with an asterisk are computed
+// by the connection attempt itself.  Since the connection attempt may be
+// started before a URLRequest, the starred times may occur before, during, or
+// after the request_start and proxy events.
+struct NET_EXPORT LoadTimingInfo {
+  // Contains the LoadTimingInfo events related to establishing a connection.
+  // These are all set by ConnectJobs.
+  struct NET_EXPORT_PRIVATE ConnectTiming {
+    ConnectTiming();
+    ~ConnectTiming();
+
+    // The time spent looking up the host's DNS address.  Null for requests that
+    // used proxies to look up the DNS address.  Also null for SOCKS4 proxies,
+    // since the DNS address is only looked up after the connection is
+    // established, which results in unexpected event ordering.
+    // TODO(mmenke):  The SOCKS4 event ordering could be refactored to allow
+    //                these times to be non-null.
+    base::TimeTicks dns_start;
+    base::TimeTicks dns_end;
+
+    // The time spent establishing the connection. Connect time includes proxy
+    // connect times (Though not proxy_resolve times), DNS lookup times, time
+    // spent waiting in certain queues, TCP, and SSL time.
+    // TODO(mmenke):  For proxies, this includes time spent blocking on higher
+    //                level socket pools.  Fix this.
+    // TODO(mmenke):  Retried connections to the same server should apparently
+    //                be included in this time.  Consider supporting that.
+    //                Since the network stack has multiple notions of a "retry",
+    //                handled at different levels, this may not be worth
+    //                worrying about - backup jobs, reused socket failure,
+    //                multiple round authentication.
+    base::TimeTicks connect_start;
+    base::TimeTicks connect_end;
+
+    // The time when the SSL handshake started / completed. For non-HTTPS
+    // requests these are null.  These times are only for the SSL connection to
+    // the final destination server, not an SSL/SPDY proxy.
+    base::TimeTicks ssl_start;
+    base::TimeTicks ssl_end;
+  };
+
+  LoadTimingInfo();
+  ~LoadTimingInfo();
+
+  // True if the socket was reused.  When true, DNS, connect, and SSL times
+  // will all be null.  When false, those times may be null, too, for non-HTTP
+  // requests, or when they don't apply to a request.
+  bool socket_reused;
+
+  // Unique socket ID, can be used to identify requests served by the same
+  // socket.
+  // TODO(mmenke):  Do something reasonable for SPDY proxies.
+  uint32 socket_log_id;
+
+  // Start time as a base::Time, so times can be coverted into actual times.
+  // Other times are recorded as TimeTicks so they are not affected by clock
+  // changes.
+  base::Time request_start_time;
+
+  base::TimeTicks request_start;
+
+  // The time spent determing which proxy to use.  Null when there is no PAC.
+  base::TimeTicks proxy_resolve_start;
+  base::TimeTicks proxy_resolve_end;
+
+  ConnectTiming connect_timing;
+
+  // The time that sending HTTP request started / ended.
+  base::TimeTicks send_start;
+  base::TimeTicks send_end;
+
+  // The time at which the end of the HTTP headers were received.
+  base::TimeTicks receive_headers_end;
+};
+
+}  // namespace net
+
+#endif  // NET_BASE_LOAD_TIMING_INFO_H_