Per-renderer WebSocket throttling

content/browser/renderer_host/websocket_dispatcher_host.cc

Index: content/browser/renderer_host/websocket_dispatcher_host.cc
diff --git a/content/browser/renderer_host/websocket_dispatcher_host.cc b/content/browser/renderer_host/websocket_dispatcher_host.cc
index d49199a7cb8f44e08ea03435a58905f63b618fc5..fc9aef4477e4a18d6f5e5ed7b3aec4486fda4839 100644
--- a/content/browser/renderer_host/websocket_dispatcher_host.cc
+++ b/content/browser/renderer_host/websocket_dispatcher_host.cc
@@ -9,6 +9,7 @@
 
 #include "base/callback.h"
 #include "base/logging.h"
+#include "base/rand_util.h"
 #include "base/stl_util.h"
 #include "content/browser/child_process_security_policy_impl.h"
 #include "content/browser/renderer_host/websocket_host.h"
@@ -33,7 +34,12 @@ WebSocketDispatcherHost::WebSocketDispatcherHost(
       get_context_callback_(get_context_callback),
       websocket_host_factory_(
           base::Bind(&WebSocketDispatcherHost::CreateWebSocketHost,
-                     base::Unretained(this))) {}
+                     base::Unretained(this))),
+      num_pending_connections_(0),
+      num_current_succeeded_connections_(0),
+      num_previous_succeeded_connections_(0),
+      num_current_failed_connections_(0),
+      num_previous_failed_connections_(0) {}
 
 WebSocketDispatcherHost::WebSocketDispatcherHost(
     int process_id,
@@ -44,8 +50,10 @@ WebSocketDispatcherHost::WebSocketDispatcherHost(
       get_context_callback_(get_context_callback),
       websocket_host_factory_(websocket_host_factory) {}
 
-WebSocketHost* WebSocketDispatcherHost::CreateWebSocketHost(int routing_id) {
-  return new WebSocketHost(routing_id, this, get_context_callback_.Run());
+WebSocketHost* WebSocketDispatcherHost::CreateWebSocketHost(int routing_id,
+                                                            int delay_in_ms) {
+  return new WebSocketHost(routing_id, this, get_context_callback_.Run(),
+      delay_in_ms);
 }
 
 bool WebSocketDispatcherHost::OnMessageReceived(const IPC::Message& message) {
@@ -73,8 +81,23 @@ bool WebSocketDispatcherHost::OnMessageReceived(const IPC::Message& message) {
       // little extreme. So for now just ignore the bogus request.
       return true;  // We handled the message (by ignoring it).
     }
-    host = websocket_host_factory_.Run(routing_id);
+    if (num_pending_connections_ > 255) { // FIXME: 255

[Adam Rice, 2015/03/03 15:10:02]

Nitpick: use "TODO(hiroshige)" rather than "FIXME" in Chromium code.

[hiroshige, 2015/03/04 06:02:37]

Done.

+      if(!Send(new WebSocketMsg_NotifyFailure(routing_id,
+          "Error in connection establishment: net::ERR_INSUFFICIENT_RESOURCES"
+          ))) {
+        DVLOG(1) << "Sending of message type "
+                 << "WebSocketMsg_NotifyFailure failed.";
+      }
+      return true;
+    }
+    host = websocket_host_factory_.Run(routing_id, CalculateDelayInMs());
     hosts_.insert(WebSocketHostTable::value_type(routing_id, host));
+    ++num_pending_connections_;
+    if (!timer_.IsRunning())
+      timer_.Start(FROM_HERE,
+                   base::TimeDelta::FromMinutes(2),
+                   this,
+                   &WebSocketDispatcherHost::FinishThrottlingPeriod);
   }
   if (!host) {
     DVLOG(1) << "Received invalid routing ID " << routing_id
@@ -121,6 +144,15 @@ WebSocketHostState WebSocketDispatcherHost::SendAddChannelResponse(
     DeleteWebSocketHost(routing_id);
     return WEBSOCKET_HOST_DELETED;
   }
+
+  // Update throttling counters (success).
+  WebSocketHost* host = GetHost(routing_id);
+  DCHECK(host);
+  host->OnHandshakeSucceeded();
+  --num_pending_connections_;
+  DCHECK(num_pending_connections_ >= 0);

[Adam Rice, 2015/03/03 15:10:02]

Nitpick: Use DCHECK_GE().

[hiroshige, 2015/03/04 06:02:37]

Done.

+  ++num_current_succeeded_connections_;

[Adam Rice, 2015/03/03 15:10:02]

Are we sure that num_current_succeeded_connections_ can't overflow? Maybe we
should include a DCHECK?

[hiroshige, 2015/03/04 06:02:37]

About >9M successful (or failed) handshakes per second (i.e. 100ns per
handshake) would lead to overflow.
Changed to int64 and added DCHECK.

[Adam Rice, 2015/03/04 08:20:49]

9M successes per second would never be possible without radical architectural
changes, but 9M failures per second might be within reach of the very fastest
machines now that we've added a fast-path for failure. So I think switching to
int64 was a good choice.

[Adam Rice, 2015/03/04 08:35:10]

Another approach would be to stop incrementing num_current_failed_connections_
if it reaches 1<<30, and stop incrementing num_current_succeeded_connections_ if
it reaches 1<<26.

Achieving millions of failures per second might be achievable now that we've
made failing very cheap, but millions of successes per second will be impossible
for the foreseeable future on a single thread.

+
   return WEBSOCKET_HOST_ALIVE;
 }
 
@@ -200,8 +232,42 @@ WebSocketDispatcherHost::~WebSocketDispatcherHost() {
 void WebSocketDispatcherHost::DeleteWebSocketHost(int routing_id) {
   WebSocketHostTable::iterator it = hosts_.find(routing_id);
   DCHECK(it != hosts_.end());
+
+  if (!it->second->handshakeSucceeded()) {
+    // Update throttling counters (failure).
+    --num_pending_connections_;
+    DCHECK(num_pending_connections_ >= 0);
+    ++num_current_failed_connections_;
+  }
+
   delete it->second;
   hosts_.erase(it);
+
+  DCHECK(static_cast<size_t>(num_pending_connections_) <= hosts_.size());
+}
+
+int64 WebSocketDispatcherHost::CalculateDelayInMs() const {

[Adam Rice, 2015/03/03 15:10:02]

This would be a good place to have a link to the design doc to explain where
this formula came from.

[hiroshige, 2015/03/04 06:02:37]

Done.

+  int f = num_previous_failed_connections_ +
+          num_current_failed_connections_;
+  int s = num_previous_succeeded_connections_ +
+          num_current_succeeded_connections_;
+  int p = num_pending_connections_;
+  return base::RandInt(1000, 5000) *
+      (1 << std::min(p + f / (s + 1), 16)) / 65536;
+}
+
+void WebSocketDispatcherHost::FinishThrottlingPeriod() {
+  num_previous_failed_connections_ = num_current_failed_connections_;
+  num_current_failed_connections_ = 0;
+
+  num_previous_succeeded_connections_ = num_current_succeeded_connections_;
+  num_current_succeeded_connections_ = 0;
+
+  if (num_pending_connections_ == 0 &&
+      num_previous_failed_connections_ == 0 &&
+      num_previous_succeeded_connections_ == 0) {
+    timer_.Stop();
+  }
 }
 
 }  // namespace content