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 9aa7a5e2d3c64f22374cad9430d120d3e44a4aea..ab4e68b76c1c17a6e722d2e38ae2438f14478bb0 100644
--- a/content/browser/renderer_host/websocket_dispatcher_host.cc
+++ b/content/browser/renderer_host/websocket_dispatcher_host.cc
@@ -9,6 +9,8 @@
 
 #include "base/callback.h"
 #include "base/logging.h"
+#include "base/numerics/safe_conversions.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"
@@ -23,6 +25,10 @@ namespace {
 // fully-qualified every time.
 typedef WebSocketDispatcherHost::WebSocketHostState WebSocketHostState;
 
+// Max number of pending connections per WebSocketDispatcherHost
+// used for per-renderer WebSocket throttling.
+const int kMaxPendingWebSocketConnections = 255;
+
 }  // namespace
 
 WebSocketDispatcherHost::WebSocketDispatcherHost(
@@ -33,7 +39,12 @@ 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,
@@ -42,10 +53,18 @@ WebSocketDispatcherHost::WebSocketDispatcherHost(
     : BrowserMessageFilter(WebSocketMsgStart),
       process_id_(process_id),
       get_context_callback_(get_context_callback),
-      websocket_host_factory_(websocket_host_factory) {}
+      websocket_host_factory_(websocket_host_factory),
+      num_pending_connections_(0),
+      num_current_succeeded_connections_(0),
+      num_previous_succeeded_connections_(0),
+      num_current_failed_connections_(0),
+      num_previous_failed_connections_(0) {}
 
-WebSocketHost* WebSocketDispatcherHost::CreateWebSocketHost(int routing_id) {
-  return new WebSocketHost(routing_id, this, get_context_callback_.Run());
+WebSocketHost* WebSocketDispatcherHost::CreateWebSocketHost(
+    int routing_id,
+    base::TimeDelta delay) {
+  return new WebSocketHost(
+      routing_id, this, get_context_callback_.Run(), delay);
 }
 
 bool WebSocketDispatcherHost::OnMessageReceived(const IPC::Message& message) {
@@ -73,8 +92,24 @@ 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_ >= kMaxPendingWebSocketConnections) {
+      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, CalculateDelay());
     hosts_.insert(WebSocketHostTable::value_type(routing_id, host));
+    ++num_pending_connections_;
+    if (!throttling_period_timer_.IsRunning())
+      throttling_period_timer_.Start(
+          FROM_HERE,
+          base::TimeDelta::FromMinutes(2),
+          this,
+          &WebSocketDispatcherHost::ThrottlingPeriodTimerCallback);
   }
   if (!host) {
     DVLOG(1) << "Received invalid routing ID " << routing_id
@@ -112,6 +147,14 @@ WebSocketHostState WebSocketDispatcherHost::SendAddChannelResponse(
     int routing_id,
     const std::string& selected_protocol,
     const std::string& extensions) {
+  // Update throttling counters (success).
+  WebSocketHost* host = GetHost(routing_id);
+  DCHECK(host);
+  host->OnHandshakeSucceeded();
+  --num_pending_connections_;
+  DCHECK_GE(num_pending_connections_, 0);
+  ++num_current_succeeded_connections_;
+
   return SendOrDrop(new WebSocketMsg_AddChannelResponse(
       routing_id, selected_protocol, extensions));
 }
@@ -192,8 +235,55 @@ WebSocketDispatcherHost::~WebSocketDispatcherHost() {
 void WebSocketDispatcherHost::DeleteWebSocketHost(int routing_id) {
   WebSocketHostTable::iterator it = hosts_.find(routing_id);
   DCHECK(it != hosts_.end());
+  DCHECK(it->second);
+  if (!it->second->handshake_succeeded()) {
+    // Update throttling counters (failure).
+    --num_pending_connections_;
+    DCHECK_GE(num_pending_connections_, 0);
+    ++num_current_failed_connections_;
+  }
+
   delete it->second;
   hosts_.erase(it);
+
+  DCHECK_LE(base::checked_cast<size_t>(num_pending_connections_),
+            hosts_.size());
+}
+
+int64_t WebSocketDispatcherHost::num_failed_connections() const {
+  return num_previous_failed_connections_ +
+         num_current_failed_connections_;
+}
+
+int64_t WebSocketDispatcherHost::num_succeeded_connections() const {
+  return num_previous_succeeded_connections_ +
+         num_current_succeeded_connections_;
+}
+
+// Calculate delay as described in
+// the per-renderer WebSocket throttling design doc:
+// https://docs.google.com/document/d/1aw2oN5PKfk-1gLnBrlv1OwLA8K3-ykM2ckwX2lubTg4/edit?usp=sharing
+base::TimeDelta WebSocketDispatcherHost::CalculateDelay() const {
+  int64_t f = num_failed_connections();
+  int64_t s = num_succeeded_connections();
+  int p = num_pending_connections();
+  return base::TimeDelta::FromMilliseconds(
+      base::RandInt(1000, 5000) *
+      (1 << std::min(p + f / (s + 1), INT64_C(16))) / 65536);
+}
+
+void WebSocketDispatcherHost::ThrottlingPeriodTimerCallback() {
+  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) {
+    throttling_period_timer_.Stop();
+  }
 }
 
 }  // namespace content