Slow start pipelining.

net/http/http_pipelined_host_impl.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_impl.h"
+
+#include "base/stl_util.h"
+#include "net/http/http_pipelined_connection_impl.h"
+#include "net/http/http_pipelined_stream.h"
+
+namespace net {
+
+// TODO(simonjam): Run experiments to see what value minimizes evictions without
+// costing too much performance. Until then, this is just a bad guess.
+static const int kNumKnownSuccessesThreshold = 3;
+
+class HttpPipelinedConnectionImplFactory :
+    public HttpPipelinedConnection::Factory {
+ public:
+  HttpPipelinedConnection* CreateNewPipeline(
+      ClientSocketHandle* connection,
+      HttpPipelinedConnection::Delegate* delegate,
+      const SSLConfig& used_ssl_config,
+      const ProxyInfo& used_proxy_info,
+      const BoundNetLog& net_log,
+      bool was_npn_negotiated) OVERRIDE {
+    return new HttpPipelinedConnectionImpl(connection, delegate,
+                                           used_ssl_config, used_proxy_info,
+                                           net_log, was_npn_negotiated);
+  }
+};
+
+HttpPipelinedHostImpl::HttpPipelinedHostImpl(
+    HttpPipelinedHost::Delegate* delegate,
+    const HostPortPair& origin,
+    HttpPipelinedConnection::Factory* factory,
+    Capability capability)
+    : delegate_(delegate),
+      origin_(origin),
+      factory_(factory),
+      capability_(capability) {
+  if (!factory) {
+    factory_.reset(new HttpPipelinedConnectionImplFactory());
+  }
+}
+
+HttpPipelinedHostImpl::~HttpPipelinedHostImpl() {
+  CHECK(pipelines_.empty());
+}
+
+HttpPipelinedStream* HttpPipelinedHostImpl::CreateStreamOnNewPipeline(
+    ClientSocketHandle* connection,
+    const SSLConfig& used_ssl_config,
+    const ProxyInfo& used_proxy_info,
+    const BoundNetLog& net_log,
+    bool was_npn_negotiated) {
+  if (capability_ == INCAPABLE) {
+    return NULL;
+  }
+  HttpPipelinedConnection* pipeline = factory_->CreateNewPipeline(
+      connection, this, used_ssl_config, used_proxy_info, net_log,
+      was_npn_negotiated);
+  PipelineInfo info;
+  pipelines_.insert(std::make_pair(pipeline, info));
+  return pipeline->CreateNewStream();
+}
+
+HttpPipelinedStream* HttpPipelinedHostImpl::CreateStreamOnExistingPipeline() {
+  HttpPipelinedConnection* available_pipeline = NULL;
+  for (PipelineInfoMap::iterator it = pipelines_.begin();
+       it != pipelines_.end(); ++it) {
+    if (it->first->usable() &&
+        it->first->active() &&
+        it->first->depth() < GetPipelineCapacity() &&
+        (!available_pipeline ||
+         it->first->depth() < available_pipeline->depth())) {
+      available_pipeline = it->first;
+    }
+  }
+  if (!available_pipeline) {
+    return NULL;
+  }
+  return available_pipeline->CreateNewStream();
+}
+
+bool HttpPipelinedHostImpl::IsExistingPipelineAvailable() const {
+  for (PipelineInfoMap::const_iterator it = pipelines_.begin();
+       it != pipelines_.end(); ++it) {
+    if (it->first->usable() &&
+        it->first->active() &&
+        it->first->depth() < GetPipelineCapacity()) {
+      return true;
+    }
+  }
+  return false;
+}
+
+const HostPortPair& HttpPipelinedHostImpl::origin() const {
+  return origin_;
+}
+
+void HttpPipelinedHostImpl::OnPipelineEmpty(HttpPipelinedConnection* pipeline) {
+  CHECK(ContainsKey(pipelines_, pipeline));
+  pipelines_.erase(pipeline);
+  delete pipeline;
+  if (pipelines_.empty()) {
+    delegate_->OnHostIdle(this);
+    // WARNING: We'll probably be deleted here.
+  }
+}
+
+void HttpPipelinedHostImpl::OnPipelineHasCapacity(
+    HttpPipelinedConnection* pipeline) {
+  CHECK(ContainsKey(pipelines_, pipeline));
+  if (pipeline->usable() &&
+      capability_ != INCAPABLE &&
+      pipeline->depth() < GetPipelineCapacity()) {
+    delegate_->OnHostHasAdditionalCapacity(this);
+  }
+  if (!pipeline->depth()) {
+    OnPipelineEmpty(pipeline);
+    // WARNING: We might be deleted here.
+  }
+}
+
+void HttpPipelinedHostImpl::OnPipelineFeedback(
+    HttpPipelinedConnection* pipeline,
+    HttpPipelinedConnection::Feedback feedback) {
+  CHECK(ContainsKey(pipelines_, pipeline));
+  switch (feedback) {
+    case HttpPipelinedConnection::OK:
+      ++pipelines_[pipeline].num_successes;
+      if (capability_ == UNKNOWN) {
+        capability_ = PROBABLY_CAPABLE;
+        for (PipelineInfoMap::iterator it = pipelines_.begin();
+             it != pipelines_.end(); ++it) {
+          OnPipelineHasCapacity(it->first);

[mmenke, 2011/12/01 17:22:48]

We may want a unit test for this behavior at some point, but think we can live
without one for now.

[James Simonsen, 2011/12/01 20:36:42]

Done.

+        }
+      } else if (capability_ == PROBABLY_CAPABLE &&
+                 pipelines_[pipeline].num_successes >=
+                 kNumKnownSuccessesThreshold) {

[mmenke, 2011/12/01 17:22:48]

Could you indent this 4 more spaces, to make it a little clearer that it's a
continuation of the comparison from the previous line?

[James Simonsen, 2011/12/01 20:36:42]

Done.

+        capability_ = CAPABLE;
+        delegate_->OnHostDeterminedCapability(this, CAPABLE);
+      }
+      break;
+
+    case HttpPipelinedConnection::PIPELINE_SOCKET_ERROR:
+    case HttpPipelinedConnection::OLD_HTTP_VERSION:
+      capability_ = INCAPABLE;
+      delegate_->OnHostDeterminedCapability(this, INCAPABLE);
+      break;
+
+    case HttpPipelinedConnection::MUST_CLOSE_CONNECTION:
+      break;
+  }
+}
+
+int HttpPipelinedHostImpl::GetPipelineCapacity() const {
+  int capacity = 0;
+  switch (capability_) {
+    case CAPABLE:
+    case PROBABLY_CAPABLE:
+      capacity = max_pipeline_depth();
+      break;
+
+    case INCAPABLE:
+      CHECK(false);
+
+    case UNKNOWN:
+      capacity = 1;
+      break;
+
+    default:
+      CHECK(false) << "Unkown pipeline capability: " << capability_;
+  }
+  return capacity;
+}
+
+HttpPipelinedHostImpl::PipelineInfo::PipelineInfo()
+    : num_successes(0) {
+}
+
+}  // namespace net