[GCM] Add port 443 fallback logic and histograms

google_apis/gcm/engine/connection_factory_impl.cc

Index: google_apis/gcm/engine/connection_factory_impl.cc
diff --git a/google_apis/gcm/engine/connection_factory_impl.cc b/google_apis/gcm/engine/connection_factory_impl.cc
index ebfd367c9a85c571da3b3914477dab303e1fc673..25c7e5118b73e58737df1c60a0ec5ff9aa06d91e 100644
--- a/google_apis/gcm/engine/connection_factory_impl.cc
+++ b/google_apis/gcm/engine/connection_factory_impl.cc
@@ -41,11 +41,12 @@ bool ShouldRestorePreviousBackoff(const base::TimeTicks& login_time,
 }  // namespace
 
 ConnectionFactoryImpl::ConnectionFactoryImpl(
-    const GURL& mcs_endpoint,
+    const std::vector<GURL>& mcs_endpoints,
     const net::BackoffEntry::Policy& backoff_policy,
     scoped_refptr<net::HttpNetworkSession> network_session,
     net::NetLog* net_log)
-  : mcs_endpoint_(mcs_endpoint),
+  : mcs_endpoints_(mcs_endpoints),
+    current_endpoint_(0),
     backoff_policy_(backoff_policy),
     network_session_(network_session),
     bound_net_log_(
@@ -54,6 +55,7 @@ ConnectionFactoryImpl::ConnectionFactoryImpl(
     connecting_(false),
     logging_in_(false),
     weak_ptr_factory_(this) {
+  DCHECK_GE(mcs_endpoints_.size(), 1U);
 }
 
 ConnectionFactoryImpl::~ConnectionFactoryImpl() {
@@ -189,7 +191,7 @@ void ConnectionFactoryImpl::ConnectImpl() {
   DCHECK(!socket_handle_.socket());
 
   int status = network_session_->proxy_service()->ResolveProxy(
-      mcs_endpoint_,
+      mcs_endpoints_[current_endpoint_],
       &proxy_info_,
       base::Bind(&ConnectionFactoryImpl::OnProxyResolveDone,
                  weak_ptr_factory_.GetWeakPtr()),
@@ -234,13 +236,27 @@ void ConnectionFactoryImpl::OnConnectDone(int result) {
     CloseSocket();
     backoff_entry_->InformOfRequest(false);
     UMA_HISTOGRAM_SPARSE_SLOWLY("GCM.ConnectionFailureErrorCode", result);
+
+    // If there are other endpoints available, use the next endpoint on the
+    // subsequent retry.
+    current_endpoint_++;
+    if (current_endpoint_ >= mcs_endpoints_.size())
+      current_endpoint_ = 0;
     Connect();
     return;
   }
 
   UMA_HISTOGRAM_BOOLEAN("GCM.ConnectionSuccessRate", true);
+  UMA_HISTOGRAM_COUNTS("GCM.ConnectionEndpoint", current_endpoint_);

[fgorski, 2014/03/20 16:45:42]

How/what exactly do you mean to measure here? (this is related to your TODO that
follows)

[Nicolas Zea, 2014/03/20 20:10:02]

I'd like to understand what % of users are able to connect to port 443 but
unable to connect to port 5228. If it's a large amount, at some point we should
probably swap the priority order.

Granted, because this is just alternating, there'll be some noise due to those
users who are in backoff and, when their network comes online or something,
happen to then be attempting the connection to the 443 endpoint. I'm not sure
there's a better way to measure though?

+  UMA_HISTOGRAM_BOOLEAN("GCM.ConnectedViaProxy",
+                        !(proxy_info_.is_empty() || proxy_info_.is_direct()));
   ReportSuccessfulProxyConnection();
 
+  // Reset the endpoint back to the default.
+  // TODO(zea): consider prioritizing endpoints more intelligently based on
+  // which ones succeed most for this client? Although that will affect
+  // measuring the success rate of the default endpoint vs fallback.
+  current_endpoint_ = 0;
   connecting_ = false;
   logging_in_ = true;
   DVLOG(1) << "MCS endpoint socket connection success, starting login.";
@@ -300,7 +316,7 @@ void ConnectionFactoryImpl::OnProxyResolveDone(int status) {
   net::SSLConfig ssl_config;
   network_session_->ssl_config_service()->GetSSLConfig(&ssl_config);
   status = net::InitSocketHandleForTlsConnect(
-      net::HostPortPair::FromURL(mcs_endpoint_),
+      net::HostPortPair::FromURL(mcs_endpoints_[current_endpoint_]),
       network_session_.get(),
       proxy_info_,
       ssl_config,
@@ -374,7 +390,7 @@ int ConnectionFactoryImpl::ReconsiderProxyAfterError(int error) {
   }
 
   int status = network_session_->proxy_service()->ReconsiderProxyAfterError(
-      mcs_endpoint_, &proxy_info_,
+      mcs_endpoints_[current_endpoint_], &proxy_info_,
       base::Bind(&ConnectionFactoryImpl::OnProxyResolveDone,
                  weak_ptr_factory_.GetWeakPtr()),
       &pac_request_,