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..870b63070bad468c3868e4229bdb5d8f91fdd9fc 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"
@@ -23,6 +24,10 @@ namespace {
 // fully-qualified every time.
 typedef WebSocketDispatcherHost::WebSocketHostState WebSocketHostState;
 
+// Max of pending connections per WebSocketDispatcherHost

[Adam Rice, 2015/03/04 08:20:50]

Nitpick: "Max number of"

[hiroshige, 2015/03/04 11:13:15]

Done.

+// used for per-renderer WebSocket throttling.
+const int kMaxPendingWebSocketConnections = 255;
+
 }  // namespace
 
 WebSocketDispatcherHost::WebSocketDispatcherHost(
@@ -33,7 +38,12 @@ 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 +54,11 @@ 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,
+    base::TimeDelta delay) {
+  return new WebSocketHost(
+      routing_id, this, get_context_callback_.Run(), delay);
 }
 
 bool WebSocketDispatcherHost::OnMessageReceived(const IPC::Message& message) {
@@ -73,8 +86,23 @@ 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_ > 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 (!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 +149,16 @@ 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_GE(num_pending_connections_, 0);
+  ++num_current_succeeded_connections_;
+  DCHECK_LT(num_current_succeeded_connections_, kint64max / 2);

[Adam Rice, 2015/03/04 08:20:50]

I don't think the "/ 2" is doing anything useful here. It will just make anyone
reading the code confused.

[hiroshige, 2015/03/04 11:13:15]

I added "/ 2" here because this variable is used like:
"num_previous_succeeded_connections_ + num_current_succeeded_connections_".

Or should we remove this DCHECK?
(Now I made this int64_t, this cannot overflow in normal operations)

[Adam Rice, 2015/03/05 07:48:27]

Yes, just remove it. Even if there is a bug in the code this DCHECK will never
fire in practice. It's more trouble than it is worth.

[hiroshige, 2015/03/06 06:04:29]

Done.

+
   return WEBSOCKET_HOST_ALIVE;
 }
 
@@ -200,8 +238,47 @@ 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_;
+    DCHECK_LT(num_current_failed_connections_, kint64max / 2);
+  }
+
   delete it->second;
   hosts_.erase(it);
+
+  DCHECK(static_cast<size_t>(num_pending_connections_) <= hosts_.size());

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

DCHECK_LE.

Also, you should use checked_cast<> from base/safe_conversions.h instead of
static_cast here.

[hiroshige, 2015/03/04 11:13:15]

Done.

+}
+
+// Calculate delay according to

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

I think "as described in" sounds nicer than "according to".

[hiroshige, 2015/03/04 11:13:15]

Done.

+// 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_previous_failed_connections_ +
+              num_current_failed_connections_;
+  int64_t s = num_previous_succeeded_connections_ +
+              num_current_succeeded_connections_;
+  int p = num_pending_connections_;
+  return base::TimeDelta::FromMilliseconds(
+      base::RandInt(1000, 5000) *
+      (1 << std::min(p + f / (s + 1), static_cast<int64_t>(16))) / 65536);

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

I think it is probably clearer to write 16LL rather than
static_cast<int64_t>(16) here.

[hiroshige, 2015/03/04 11:13:14]

Sadly 16LL doesn't pass compilation;
std::min requires arguments have exactly the same type, and
int64_t is long in 64-bit Linux, 16LL is long long.
(16L would also fail in 32-bit environment?)

[Adam Rice, 2015/03/05 07:48:27]

Sorry. I just remembered how to do this properly. There is an INT64_C() macro in
<stdint.h> which will add the platform-appropriate suffix.

[hiroshige, 2015/03/06 06:04:29]

Done.

+}
+
+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