Slow start pipelining.

net/http/http_pipelined_host_pool.cc

 // 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.
 
 #include "net/http/http_pipelined_host_pool.h"
 
 #include "base/logging.h"
 #include "base/stl_util.h"
-#include "net/http/http_pipelined_host.h"
-#include "net/http/http_stream_factory_impl.h"
+#include "net/http/http_pipelined_host_impl.h"
 
 namespace net {
 
-HttpPipelinedHostPool::HttpPipelinedHostPool(HttpStreamFactoryImpl* factory)
-    : factory_(factory) {
+// TODO(simonjam): Run experiments with different values of this to see what
+// value is good at avoiding evictions without eating too much memory. Until
+// then, this is just a bad guess.
+static const int kNumHostsToRemember = 200;
+
+class HttpPipelinedHostImplFactory : public HttpPipelinedHost::Factory {
+ public:
+  virtual HttpPipelinedHost* CreateNewHost(
+      HttpPipelinedHost::Delegate* delegate, const HostPortPair& origin,
+      HttpPipelinedConnection::Factory* factory,
+      HttpPipelinedHost::Capability capability) OVERRIDE {
+    return new HttpPipelinedHostImpl(delegate, origin, factory, capability);
+  }
+};
+
+HttpPipelinedHostPool::HttpPipelinedHostPool(
+    Delegate* delegate,
+    HttpPipelinedHost::Factory* factory)
+    : delegate_(delegate),
+      factory_(factory),
+      known_capability_map_(kNumHostsToRemember) {
+  if (!factory) {
+    factory_.reset(new HttpPipelinedHostImplFactory);
+  }
 }
 
 HttpPipelinedHostPool::~HttpPipelinedHostPool() {
   CHECK(host_map_.empty());
 }
 
+bool HttpPipelinedHostPool::IsHostEligibleForPipelining(
+    const HostPortPair& origin) {
+  HttpPipelinedHost::Capability capability = GetHostCapability(origin);
+  return capability != HttpPipelinedHost::INCAPABLE;
+}
+
 HttpPipelinedStream* HttpPipelinedHostPool::CreateStreamOnNewPipeline(
     const HostPortPair& origin,
     ClientSocketHandle* connection,
     const SSLConfig& used_ssl_config,
     const ProxyInfo& used_proxy_info,
     const BoundNetLog& net_log,
     bool was_npn_negotiated) {
   HttpPipelinedHost* host = GetPipelinedHost(origin, true);
+  if (!host) {
+    return NULL;
+  }
   return host->CreateStreamOnNewPipeline(connection, used_ssl_config,
                                          used_proxy_info, net_log,
                                          was_npn_negotiated);
 }
 
 HttpPipelinedStream* HttpPipelinedHostPool::CreateStreamOnExistingPipeline(
     const HostPortPair& origin) {
   HttpPipelinedHost* host = GetPipelinedHost(origin, false);
   if (!host) {
     return NULL;
   }
   return host->CreateStreamOnExistingPipeline();
 }
 
 bool HttpPipelinedHostPool::IsExistingPipelineAvailableForOrigin(
     const HostPortPair& origin) {
   HttpPipelinedHost* host = GetPipelinedHost(origin, false);
   if (!host) {
     return false;
   }
   return host->IsExistingPipelineAvailable();
 }
 
 HttpPipelinedHost* HttpPipelinedHostPool::GetPipelinedHost(
     const HostPortPair& origin, bool create_if_not_found) {
-  HostMap::iterator it = host_map_.find(origin);
-  if (it != host_map_.end()) {
-    CHECK(it->second);
-    return it->second;
+  HostMap::iterator host_it = host_map_.find(origin);
+  if (host_it != host_map_.end()) {
+    CHECK(host_it->second);
+    return host_it->second;
   } else if (!create_if_not_found) {
     return NULL;
   }
-  HttpPipelinedHost* host = new HttpPipelinedHost(this, origin, NULL);
+
+  HttpPipelinedHost::Capability capability = GetHostCapability(origin);
+  if (capability == HttpPipelinedHost::INCAPABLE) {
+    return NULL;
+  }
+
+  HttpPipelinedHost* host = factory_->CreateNewHost(
+      this, origin, NULL, capability);
   host_map_[origin] = host;
   return host;
 }
 
 void HttpPipelinedHostPool::OnHostIdle(HttpPipelinedHost* host) {
   const HostPortPair& origin = host->origin();
   CHECK(ContainsKey(host_map_, origin));
-  // TODO(simonjam): We should remember the pipeline state for each host.
   host_map_.erase(origin);
   delete host;
 }
 
 void HttpPipelinedHostPool::OnHostHasAdditionalCapacity(
     HttpPipelinedHost* host) {
-  factory_->OnHttpPipelinedHostHasAdditionalCapacity(host->origin());
+  delegate_->OnHttpPipelinedHostHasAdditionalCapacity(host->origin());
+}
+
+void HttpPipelinedHostPool::OnHostDeterminedCapability(
+    HttpPipelinedHost* host,
+    HttpPipelinedHost::Capability capability) {
+  CapabilityMap::iterator known_it = known_capability_map_.Get(host->origin());
+  if (known_it == known_capability_map_.end() ||
+      known_it->second != HttpPipelinedHost::INCAPABLE) {
+    known_capability_map_.Put(host->origin(), capability);
+  }
+}
+
+HttpPipelinedHost::Capability HttpPipelinedHostPool::GetHostCapability(
+    const HostPortPair& origin) {
+  HttpPipelinedHost::Capability capability = HttpPipelinedHost::UNKNOWN;
+  CapabilityMap::const_iterator it = known_capability_map_.Get(origin);
+  if (it != known_capability_map_.end()) {
+    capability = it->second;
+  }
+  return capability;
 }
 
 }  // namespace net