nghttpx: Support multiple HTTP/2 session per worker

Currently, we use same number of HTTP/2 sessions per worker with given
backend addresses.  New option to specify the number of HTTP/2 session
per worker will follow.

src/shrpx.cc

@@ -918,6 +918,7 @@ void fill_default_config() {
   mod_config()->no_server_push = false;
   mod_config()->host_unix = false;
   mod_config()->http2_downstream_connchk = false;
+  mod_config()->http2_downstream_connections_per_worker = 0;
 }
 } // namespace
 
@@ -2064,6 +2065,11 @@ int main(int argc, char **argv) {
     }
   }
 
+  if (get_config()->http2_downstream_connections_per_worker == 0) {
+    mod_config()->http2_downstream_connections_per_worker =
+        get_config()->downstream_addrs.size();
+  }
+
   if (get_config()->rlimit_nofile) {
     struct rlimit lim = {static_cast<rlim_t>(get_config()->rlimit_nofile),
                          static_cast<rlim_t>(get_config()->rlimit_nofile)};

src/shrpx_client_handler.cc

@@ -576,6 +576,9 @@ void ClientHandler::set_should_close_after_write(bool f) {
 
 void ClientHandler::pool_downstream_connection(
     std::unique_ptr<DownstreamConnection> dconn) {
+  if (!dconn->poolable()) {
+    return;
+  }
   if (LOG_ENABLED(INFO)) {
     CLOG(INFO, this) << "Pooling downstream connection DCONN:" << dconn.get();
   }
@@ -605,7 +608,7 @@ ClientHandler::get_downstream_connection() {
     }
 
     auto dconn_pool = worker_->get_dconn_pool();
-    auto http2session = worker_->get_http2_session();
+    auto http2session = worker_->next_http2_session();
 
     if (http2session) {
       dconn = make_unique<Http2DownstreamConnection>(dconn_pool, http2session);
@@ -628,12 +631,8 @@ ClientHandler::get_downstream_connection() {
 
 SSL *ClientHandler::get_ssl() const { return conn_.tls.ssl; }
 
-Http2Session *ClientHandler::get_http2_session() const {
-  return worker_->get_http2_session();
-}
-
-ConnectBlocker *ClientHandler::get_http1_connect_blocker() const {
-  return worker_->get_http1_connect_blocker();
+ConnectBlocker *ClientHandler::get_connect_blocker() const {
+  return worker_->get_connect_blocker();
 }
 
 void ClientHandler::direct_http2_upgrade() {

src/shrpx_client_handler.h

@@ -93,8 +93,7 @@ public:
   void remove_downstream_connection(DownstreamConnection *dconn);
   std::unique_ptr<DownstreamConnection> get_downstream_connection();
   SSL *get_ssl() const;
-  Http2Session *get_http2_session() const;
-  ConnectBlocker *get_http1_connect_blocker() const;
+  ConnectBlocker *get_connect_blocker() const;
   // Call this function when HTTP/2 connection header is received at
   // the start of the connection.
   void direct_http2_upgrade();

src/shrpx_config.h

@@ -260,6 +260,7 @@ struct Config {
   size_t http2_downstream_window_bits;
   size_t http2_upstream_connection_window_bits;
   size_t http2_downstream_connection_window_bits;
+  size_t http2_downstream_connections_per_worker;
   size_t downstream_connections_per_host;
   size_t downstream_connections_per_frontend;
   // actual size of downstream_http_proxy_addr

src/shrpx_downstream_connection.h

@@ -58,6 +58,9 @@ public:
   virtual void on_upstream_change(Upstream *uptream) = 0;
   virtual int on_priority_change(int32_t pri) = 0;
 
+  // true if this object is poolable.
+  virtual bool poolable() const = 0;
+
   void set_client_handler(ClientHandler *client_handler);
   ClientHandler *get_client_handler();
   Downstream *get_downstream();

src/shrpx_http2_downstream_connection.h

@@ -62,6 +62,10 @@ public:
   virtual void on_upstream_change(Upstream *upstream) {}
   virtual int on_priority_change(int32_t pri);
 
+  // This object is not poolable because we dont' have facility to
+  // migrate to another Http2Session object.
+  virtual bool poolable() const { return false; }
+
   int send();
 
   void attach_stream_data(StreamData *sd);

src/shrpx_http2_session.cc

@@ -40,6 +40,7 @@
 #include "shrpx_ssl.h"
 #include "shrpx_http.h"
 #include "shrpx_worker.h"
+#include "shrpx_connect_blocker.h"
 #include "http2.h"
 #include "util.h"
 #include "base64.h"
@@ -140,14 +141,14 @@ void writecb(struct ev_loop *loop, ev_io *w, int revents) {
 } // namespace
 
 Http2Session::Http2Session(struct ev_loop *loop, SSL_CTX *ssl_ctx,
-                           Worker *worker)
+                           ConnectBlocker *connect_blocker, Worker *worker)
     : conn_(loop, -1, nullptr, get_config()->downstream_write_timeout,
             get_config()->downstream_read_timeout, 0, 0, 0, 0, writecb, readcb,
             timeoutcb, this),
-      worker_(worker), ssl_ctx_(ssl_ctx), session_(nullptr),
-      data_pending_(nullptr), data_pendinglen_(0), addr_idx_(0),
-      state_(DISCONNECTED), connection_check_state_(CONNECTION_CHECK_NONE),
-      flow_control_(false) {
+      worker_(worker), connect_blocker_(connect_blocker), ssl_ctx_(ssl_ctx),
+      session_(nullptr), data_pending_(nullptr), data_pendinglen_(0),
+      addr_idx_(0), state_(DISCONNECTED),
+      connection_check_state_(CONNECTION_CHECK_NONE), flow_control_(false) {
 
   read_ = write_ = &Http2Session::noop;
   on_read_ = on_write_ = &Http2Session::noop;
@@ -237,6 +238,14 @@ int Http2Session::initiate_connection() {
   int rv = 0;
 
   if (state_ == DISCONNECTED) {
+    if (connect_blocker_->blocked()) {
+      if (LOG_ENABLED(INFO)) {
+        DCLOG(INFO, this)
+            << "Downstream connection was blocked by connect_blocker";
+      }
+      return -1;
+    }
+
     auto worker_stat = worker_->get_worker_stat();
     addr_idx_ = worker_stat->next_downstream;
     ++worker_stat->next_downstream;
@@ -261,6 +270,7 @@ int Http2Session::initiate_connection() {
         get_config()->downstream_http_proxy_addr.storage.ss_family);
 
     if (conn_.fd == -1) {
+      connect_blocker_->on_failure();
       return -1;
     }
 
@@ -270,6 +280,7 @@ int Http2Session::initiate_connection() {
       SSLOG(ERROR, this) << "Failed to connect to the proxy "
                          << get_config()->downstream_http_proxy_host.get()
                          << ":" << get_config()->downstream_http_proxy_port;
+      connect_blocker_->on_failure();
       return -1;
     }
 
@@ -329,6 +340,7 @@ int Http2Session::initiate_connection() {
         conn_.fd = util::create_nonblock_socket(
             downstream_addr.addr.storage.ss_family);
         if (conn_.fd == -1) {
+          connect_blocker_->on_failure();
           return -1;
         }
 
@@ -337,6 +349,7 @@ int Http2Session::initiate_connection() {
                      const_cast<sockaddr *>(&downstream_addr.addr.sa),
                      downstream_addr.addrlen);
         if (rv != 0 && errno != EINPROGRESS) {
+          connect_blocker_->on_failure();
           return -1;
         }
 
@@ -358,12 +371,14 @@ int Http2Session::initiate_connection() {
             downstream_addr.addr.storage.ss_family);
 
         if (conn_.fd == -1) {
+          connect_blocker_->on_failure();
           return -1;
         }
 
         rv = connect(conn_.fd, const_cast<sockaddr *>(&downstream_addr.addr.sa),
                      downstream_addr.addrlen);
         if (rv != 0 && errno != EINPROGRESS) {
+          connect_blocker_->on_failure();
           return -1;
         }
 
@@ -1377,7 +1392,9 @@ void Http2Session::signal_write() {
       LOG(INFO) << "Start connecting to backend server";
     }
     if (initiate_connection() != 0) {
-      SSLOG(FATAL, this) << "Could not initiate backend connection";
+      if (LOG_ENABLED(INFO)) {
+        SSLOG(INFO, this) << "Could not initiate backend connection";
+      }
       disconnect(true);
     }
     break;
@@ -1513,6 +1530,8 @@ int Http2Session::connected() {
     return -1;
   }
 
+  connect_blocker_->on_success();
+
   if (LOG_ENABLED(INFO)) {
     SSLOG(INFO, this) << "Connection established";
   }

src/shrpx_http2_session.h

@@ -47,6 +47,7 @@ namespace shrpx {
 
 class Http2DownstreamConnection;
 class Worker;
+class ConnectBlocker;
 
 struct StreamData {
   Http2DownstreamConnection *dconn;
@@ -54,7 +55,8 @@ struct StreamData {
 
 class Http2Session {
 public:
-  Http2Session(struct ev_loop *loop, SSL_CTX *ssl_ctx, Worker *worker);
+  Http2Session(struct ev_loop *loop, SSL_CTX *ssl_ctx,
+               ConnectBlocker *connect_blocker, Worker *worker);
   ~Http2Session();
 
   int check_cert();
@@ -192,6 +194,7 @@ private:
   // Used to parse the response from HTTP proxy
   std::unique_ptr<http_parser> proxy_htp_;
   Worker *worker_;
+  ConnectBlocker *connect_blocker_;
   // NULL if no TLS is configured
   SSL_CTX *ssl_ctx_;
   nghttp2_session *session_;

src/shrpx_http2_upstream.cc

@@ -1200,8 +1200,6 @@ Downstream *Http2Upstream::find_downstream(int32_t stream_id) {
   return downstream_queue_.find(stream_id);
 }
 
-nghttp2_session *Http2Upstream::get_http2_session() { return session_; }
-
 // WARNING: Never call directly or indirectly nghttp2_session_send or
 // nghttp2_session_recv. These calls may delete downstream.
 int Http2Upstream::on_downstream_header_complete(Downstream *downstream) {

src/shrpx_http2_upstream.h

@@ -64,8 +64,6 @@ public:
   void remove_downstream(Downstream *downstream);
   Downstream *find_downstream(int32_t stream_id);
 
-  nghttp2_session *get_http2_session();
-
   int rst_stream(Downstream *downstream, uint32_t error_code);
   int terminate_session(uint32_t error_code);
   int error_reply(Downstream *downstream, unsigned int status_code);

src/shrpx_http_downstream_connection.cc

@@ -130,7 +130,7 @@ int HttpDownstreamConnection::attach_downstream(Downstream *downstream) {
   }
 
   if (conn_.fd == -1) {
-    auto connect_blocker = client_handler_->get_http1_connect_blocker();
+    auto connect_blocker = client_handler_->get_connect_blocker();
 
     if (connect_blocker->blocked()) {
       if (LOG_ENABLED(INFO)) {
@@ -768,7 +768,7 @@ int HttpDownstreamConnection::on_write() {
 }
 
 int HttpDownstreamConnection::on_connect() {
-  auto connect_blocker = client_handler_->get_http1_connect_blocker();
+  auto connect_blocker = client_handler_->get_connect_blocker();
 
   if (!util::check_socket_connected(conn_.fd)) {
     conn_.wlimit.stopw();

src/shrpx_http_downstream_connection.h

@@ -59,6 +59,8 @@ public:
   virtual void on_upstream_change(Upstream *upstream);
   virtual int on_priority_change(int32_t pri) { return 0; }
 
+  virtual bool poolable() const { return true; }
+
   int on_connect();
   void signal_write();
 

src/shrpx_spdy_upstream.cc

@@ -821,8 +821,6 @@ Downstream *SpdyUpstream::find_downstream(int32_t stream_id) {
   return downstream_queue_.find(stream_id);
 }
 
-spdylay_session *SpdyUpstream::get_http2_session() { return session_; }
-
 // WARNING: Never call directly or indirectly spdylay_session_send or
 // spdylay_session_recv. These calls may delete downstream.
 int SpdyUpstream::on_downstream_header_complete(Downstream *downstream) {

src/shrpx_spdy_upstream.h

@@ -60,8 +60,6 @@ public:
   void remove_downstream(Downstream *downstream);
   Downstream *find_downstream(int32_t stream_id);
 
-  spdylay_session *get_http2_session();
-
   int rst_stream(Downstream *downstream, int status_code);
   int error_reply(Downstream *downstream, unsigned int status_code);
 

src/shrpx_worker.cc

@@ -51,17 +51,20 @@ void eventcb(struct ev_loop *loop, ev_async *w, int revents) {
 Worker::Worker(struct ev_loop *loop, SSL_CTX *sv_ssl_ctx, SSL_CTX *cl_ssl_ctx,
                ssl::CertLookupTree *cert_tree,
                const std::shared_ptr<TicketKeys> &ticket_keys)
-    : loop_(loop), sv_ssl_ctx_(sv_ssl_ctx), cl_ssl_ctx_(cl_ssl_ctx),
-      cert_tree_(cert_tree), ticket_keys_(ticket_keys),
+    : next_http2session_(0), loop_(loop), sv_ssl_ctx_(sv_ssl_ctx),
+      cl_ssl_ctx_(cl_ssl_ctx), cert_tree_(cert_tree), ticket_keys_(ticket_keys),
+      connect_blocker_(make_unique<ConnectBlocker>(loop_)),
       graceful_shutdown_(false) {
   ev_async_init(&w_, eventcb);
   w_.data = this;
   ev_async_start(loop_, &w_);
 
   if (get_config()->downstream_proto == PROTO_HTTP2) {
-    http2session_ = make_unique<Http2Session>(loop_, cl_ssl_ctx, this);
-  } else {
-    http1_connect_blocker_ = make_unique<ConnectBlocker>(loop_);
+    auto n = get_config()->http2_downstream_connections_per_worker;
+    for (; n > 0; --n) {
+      http2sessions_.push_back(make_unique<Http2Session>(
+          loop_, cl_ssl_ctx, connect_blocker_.get(), this));
+    }
   }
 }
 
@@ -185,10 +188,22 @@ WorkerStat *Worker::get_worker_stat() { return &worker_stat_; }
 
 DownstreamConnectionPool *Worker::get_dconn_pool() { return &dconn_pool_; }
 
-Http2Session *Worker::get_http2_session() const { return http2session_.get(); }
+Http2Session *Worker::next_http2_session() {
+  if (http2sessions_.empty()) {
+    return nullptr;
+  }
 
-ConnectBlocker *Worker::get_http1_connect_blocker() const {
-  return http1_connect_blocker_.get();
+  auto res = http2sessions_[next_http2session_].get();
+  ++next_http2session_;
+  if (next_http2session_ >= http2sessions_.size()) {
+    next_http2session_ = 0;
+  }
+
+  return res;
+}
+
+ConnectBlocker *Worker::get_connect_blocker() const {
+  return connect_blocker_.get();
 }
 
 struct ev_loop *Worker::get_loop() const {

src/shrpx_worker.h

@@ -29,6 +29,7 @@
 
 #include <mutex>
 #include <deque>
+#include <vector>
 #include <thread>
 #ifndef NOTHREADS
 #include <future>
@@ -94,8 +95,8 @@ public:
   void set_ticket_keys(std::shared_ptr<TicketKeys> ticket_keys);
   WorkerStat *get_worker_stat();
   DownstreamConnectionPool *get_dconn_pool();
-  Http2Session *get_http2_session() const;
-  ConnectBlocker *get_http1_connect_blocker() const;
+  Http2Session *next_http2_session();
+  ConnectBlocker *get_connect_blocker() const;
   struct ev_loop *get_loop() const;
   SSL_CTX *get_sv_ssl_ctx() const;
   SSL_CTX *get_cl_ssl_ctx() const;
@@ -104,6 +105,8 @@ public:
   bool get_graceful_shutdown() const;
 
 private:
+  std::vector<std::unique_ptr<Http2Session>> http2sessions_;
+  size_t next_http2session_;
 #ifndef NOTHREADS
   std::future<void> fut_;
 #endif // NOTHREADS
@@ -121,8 +124,7 @@ private:
   ssl::CertLookupTree *cert_tree_;
 
   std::shared_ptr<TicketKeys> ticket_keys_;
-  std::unique_ptr<Http2Session> http2session_;
-  std::unique_ptr<ConnectBlocker> http1_connect_blocker_;
+  std::unique_ptr<ConnectBlocker> connect_blocker_;
 
   bool graceful_shutdown_;
 };