Revert "Fix connection reuse by delaying a poll cycle. (envoyproxy#73)"

This reverts commit bc63ae7.

Signed-off-by: Piotr Sikora <piotrsikora@google.com>

source/common/http/http1/conn_pool.cc

@@ -30,10 +30,6 @@ ConnPoolImpl::ConnPoolImpl(Event::Dispatcher& dispatcher, Upstream::HostConstSha
       upstream_ready_timer_(dispatcher_.createTimer([this]() { onUpstreamReady(); })) {}
 
 ConnPoolImpl::~ConnPoolImpl() {
-  while (!delayed_clients_.empty()) {
-    delayed_clients_.front()->codec_client_->close();
-  }
-
   while (!ready_clients_.empty()) {
     ready_clients_.front()->codec_client_->close();
   }
@@ -151,12 +147,7 @@ void ConnPoolImpl::onConnectionEvent(ActiveClient& client, Network::ConnectionEv
     } else if (!client.connect_timer_) {
       // The connect timer is destroyed on connect. The lack of a connect timer means that this
       // client is idle and in the ready pool.
-      if (client.delayed_) {
-        client.delayed_ = 0;
-        removed = client.removeFromList(delayed_clients_);
-      } else {
-        removed = client.removeFromList(ready_clients_);
-      }
+      removed = client.removeFromList(ready_clients_);
       check_for_drained = false;
     } else {
       // The only time this happens is if we actually saw a connect failure.
@@ -231,20 +222,6 @@ void ConnPoolImpl::onResponseComplete(ActiveClient& client) {
 
 void ConnPoolImpl::onUpstreamReady() {
   upstream_ready_enabled_ = false;
-  auto it = delayed_clients_.begin();
-  while (it != delayed_clients_.end()) {
-    ActiveClient& client = **it;
-    it++; // Move forward before moveBetweenLists which would invalidate 'it'.
-    client.delayed_--;
-    if (client.delayed_ == 0) {
-      ENVOY_CONN_LOG(debug, "moving from delay to ready", *client.codec_client_);
-      client.moveBetweenLists(delayed_clients_, ready_clients_);
-    }
-  }
-  if (!delayed_clients_.empty()) {
-    upstream_ready_enabled_ = true;
-    upstream_ready_timer_->enableTimer(std::chrono::milliseconds(0));
-  }
   while (!pending_requests_.empty() && !ready_clients_.empty()) {
     ActiveClient& client = *ready_clients_.front();
     ENVOY_CONN_LOG(debug, "attaching to next request", *client.codec_client_);
@@ -259,13 +236,7 @@ void ConnPoolImpl::onUpstreamReady() {
 
 void ConnPoolImpl::processIdleClient(ActiveClient& client, bool delay) {
   client.stream_wrapper_.reset();
-  if (delay) {
-    ENVOY_CONN_LOG(debug, "moving to delay", *client.codec_client_);
-    // N.B. libevent does not guarantee ordering of events, so to ensure that the delayed client
-    // experiences a poll cycle before being made ready, delay for 2 event loops.
-    client.delayed_ = 2;
-    client.moveBetweenLists(busy_clients_, delayed_clients_);
-  } else if (pending_requests_.empty()) {
+  if (pending_requests_.empty() || delay) {
     // There is nothing to service or delayed processing is requested, so just move the connection
     // into the ready list.
     ENVOY_CONN_LOG(debug, "moving to ready", *client.codec_client_);
@@ -279,7 +250,7 @@ void ConnPoolImpl::processIdleClient(ActiveClient& client, bool delay) {
     pending_requests_.pop_back();
   }
 
-  if (!delayed_clients_.empty() && !upstream_ready_enabled_) {
+  if (delay && !pending_requests_.empty() && !upstream_ready_enabled_) {
     upstream_ready_enabled_ = true;
     upstream_ready_timer_->enableTimer(std::chrono::milliseconds(0));
   }

source/common/http/http1/conn_pool.h

@@ -102,7 +102,6 @@ class ConnPoolImpl : public ConnectionPool::Instance, public ConnPoolImplBase {
     Event::TimerPtr connect_timer_;
     Stats::TimespanPtr conn_length_;
     uint64_t remaining_requests_;
-    int delayed_{0};
   };
 
   typedef std::unique_ptr<ActiveClient> ActiveClientPtr;
@@ -119,7 +118,6 @@ class ConnPoolImpl : public ConnectionPool::Instance, public ConnPoolImplBase {
 
   Stats::TimespanPtr conn_connect_ms_;
   Event::Dispatcher& dispatcher_;
-  std::list<ActiveClientPtr> delayed_clients_;
   std::list<ActiveClientPtr> ready_clients_;
   std::list<ActiveClientPtr> busy_clients_;
   std::list<DrainedCb> drained_callbacks_;