Slow start pipelining.

net/http/http_pipelined_host_pool.h

 // Copyright (c) 2011 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_PIPELINED_HOST_POOL_H_
 #define NET_HTTP_HTTP_PIPELINED_HOST_POOL_H_
 #pragma once
 
 #include <map>
 
 #include "base/basictypes.h"
+#include "base/gtest_prod_util.h"
+#include "base/memory/mru_cache.h"
+#include "base/memory/scoped_ptr.h"
 #include "net/http/http_pipelined_host.h"
 
 namespace net {
 
 class HostPortPair;
 class HttpPipelinedStream;
-class HttpStreamFactoryImpl;
 
 // Manages all of the pipelining state for specific host with active pipelined
 // HTTP requests. Manages connection jobs, constructs pipelined streams, and
 // assigns requests to the least loaded pipelined connection.
-class HttpPipelinedHostPool : public HttpPipelinedHost::Delegate {
+class NET_EXPORT_PRIVATE HttpPipelinedHostPool
+    : public HttpPipelinedHost::Delegate {
  public:
-  explicit HttpPipelinedHostPool(HttpStreamFactoryImpl* factory);
-  ~HttpPipelinedHostPool();
+  class Delegate {
+   public:
+    // Called when a HttpPipelinedHost has new capacity. Attempts to allocate
+    // any pending pipeline-capable requests to pipelines.
+    virtual void OnHttpPipelinedHostHasAdditionalCapacity(
+        const HostPortPair& origin) = 0;
+  };
+
+  HttpPipelinedHostPool(Delegate* delegate,
+                        HttpPipelinedHost::Factory* factory);
+  virtual ~HttpPipelinedHostPool();
+
+  // Returns true if pipelining might work for |origin|. Generally, this returns
+  // true, unless |origin| is known to have failed pipelining recently.
+  bool IsHostEligibleForPipelining(const HostPortPair& origin);
 
   // Constructs a new pipeline on |connection| and returns a new
   // HttpPipelinedStream that uses it.
   HttpPipelinedStream* CreateStreamOnNewPipeline(
       const HostPortPair& origin,
       ClientSocketHandle* connection,
       const SSLConfig& used_ssl_config,
       const ProxyInfo& used_proxy_info,
       const BoundNetLog& net_log,
       bool was_npn_negotiated);
 
   // Tries to find an existing pipeline with capacity for a new request. If
   // successful, returns a new stream on that pipeline. Otherwise, returns NULL.
   HttpPipelinedStream* CreateStreamOnExistingPipeline(
       const HostPortPair& origin);
 
   // Returns true if a pipelined connection already exists for this origin and
   // can accept new requests.
   bool IsExistingPipelineAvailableForOrigin(const HostPortPair& origin);
 
   // Callbacks for HttpPipelinedHost.
   virtual void OnHostIdle(HttpPipelinedHost* host) OVERRIDE;
 
   virtual void OnHostHasAdditionalCapacity(HttpPipelinedHost* host) OVERRIDE;
 
+  virtual void OnHostDeterminedCapability(
+      HttpPipelinedHost* host,
+      HttpPipelinedHost::Capability capability) OVERRIDE;
+
  private:
+  typedef base::MRUCache<HostPortPair,
+                         HttpPipelinedHost::Capability> CapabilityMap;
   typedef std::map<const HostPortPair, HttpPipelinedHost*> HostMap;
 
   HttpPipelinedHost* GetPipelinedHost(const HostPortPair& origin,
                                       bool create_if_not_found);
 
-  HttpStreamFactoryImpl* factory_;
+  HttpPipelinedHost::Capability GetHostCapability(const HostPortPair& origin);
+
+  Delegate* delegate_;
+  scoped_ptr<HttpPipelinedHost::Factory> factory_;
   HostMap host_map_;
+  CapabilityMap known_capability_map_;
 
   DISALLOW_COPY_AND_ASSIGN(HttpPipelinedHostPool);
 };
 
 }  // namespace net
 
 #endif  // NET_HTTP_HTTP_PIPELINED_HOST_POOL_H_