nghttpx: Support multiple -b option for HTTP/2 backend

src/shrpx.cc

@@ -949,13 +949,10 @@ Options:
 
 Connections:
   -b, --backend=<HOST,PORT>
-              Set backend host and port.  For HTTP/1 backend, multiple
-              backend addresses are accepted by repeating this option.
-              HTTP/2  backend   does  not  support   multiple  backend
-              addresses  and the  first occurrence  of this  option is
-              used.  UNIX domain socket  can be specified by prefixing
-              path        name        with       "unix:"        (e.g.,
-              unix:/var/run/backend.sock)
+              Set  backend  host  and   port.   The  multiple  backend
+              addresses are  accepted by repeating this  option.  UNIX
+              domain socket  can be  specified by prefixing  path name
+              with "unix:" (e.g., unix:/var/run/backend.sock)
               Default: )" << DEFAULT_DOWNSTREAM_HOST << ","
       << DEFAULT_DOWNSTREAM_PORT << R"(
   -f, --frontend=<HOST,PORT>

src/shrpx_http2_downstream_connection.cc

@@ -258,15 +258,20 @@ int Http2DownstreamConnection::push_request_headers() {
                          get_config()->client_proxy ||
                          downstream_->get_request_method() == "CONNECT";
 
+  // http2session_ has already in CONNECTED state, so we can get
+  // addr_idx here.
+  auto addr_idx = http2session_->get_addr_idx();
+  auto &downstream_addr = get_config()->downstream_addrs[addr_idx];
+
   const char *authority = nullptr, *host = nullptr;
   if (!no_host_rewrite) {
     // HTTP/2 backend does not support multiple address, so we always
     // use index = 0.
     if (!downstream_->get_request_http2_authority().empty()) {
-      authority = get_config()->downstream_addrs[0].hostport.get();
+      authority = downstream_addr.hostport.get();
     }
     if (downstream_->get_request_header(http2::HD_HOST)) {
-      host = get_config()->downstream_addrs[0].hostport.get();
+      host = downstream_addr.hostport.get();
     }
   } else {
     if (!downstream_->get_request_http2_authority().empty()) {
@@ -281,7 +286,7 @@ int Http2DownstreamConnection::push_request_headers() {
   if (!authority && !host) {
     // upstream is HTTP/1.0.  We use backend server's host
     // nonetheless.
-    host = get_config()->downstream_addrs[0].hostport.get();
+    host = downstream_addr.hostport.get();
   }
 
   if (authority) {

src/shrpx_http2_session.cc

@@ -39,6 +39,7 @@
 #include "shrpx_client_handler.h"
 #include "shrpx_ssl.h"
 #include "shrpx_http.h"
+#include "shrpx_worker.h"
 #include "http2.h"
 #include "util.h"
 #include "base64.h"
@@ -138,13 +139,15 @@ void writecb(struct ev_loop *loop, ev_io *w, int revents) {
 }
 } // namespace
 
-Http2Session::Http2Session(struct ev_loop *loop, SSL_CTX *ssl_ctx)
+Http2Session::Http2Session(struct ev_loop *loop, SSL_CTX *ssl_ctx,
+                           Worker *worker)
     : conn_(loop, -1, nullptr, get_config()->downstream_write_timeout,
             get_config()->downstream_read_timeout, 0, 0, 0, 0, writecb, readcb,
             timeoutcb, this),
-      ssl_ctx_(ssl_ctx), session_(nullptr), data_pending_(nullptr),
-      data_pendinglen_(0), state_(DISCONNECTED),
-      connection_check_state_(CONNECTION_CHECK_NONE), flow_control_(false) {
+      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) {
 
   read_ = write_ = &Http2Session::noop;
   on_read_ = on_write_ = &Http2Session::noop;
@@ -185,6 +188,8 @@ int Http2Session::disconnect(bool hard) {
 
   conn_.disconnect();
 
+  addr_idx_ = 0;
+
   if (proxy_htp_) {
     proxy_htp_.reset();
   }
@@ -230,6 +235,21 @@ int Http2Session::check_cert() { return ssl::check_cert(conn_.tls.ssl); }
 
 int Http2Session::initiate_connection() {
   int rv = 0;
+
+  if (state_ == DISCONNECTED) {
+    auto worker_stat = worker_->get_worker_stat();
+    addr_idx_ = worker_stat->next_downstream;
+    ++worker_stat->next_downstream;
+    worker_stat->next_downstream %= get_config()->downstream_addrs.size();
+
+    if (LOG_ENABLED(INFO)) {
+      SSLOG(INFO, this) << "Using downstream address idx=" << addr_idx_
+                        << " out of " << get_config()->downstream_addrs.size();
+    }
+  }
+
+  auto &downstream_addr = get_config()->downstream_addrs[addr_idx_];
+
   if (get_config()->downstream_http_proxy_host && state_ == DISCONNECTED) {
     if (LOG_ENABLED(INFO)) {
       SSLOG(INFO, this) << "Connecting to the proxy "
@@ -292,7 +312,7 @@ int Http2Session::initiate_connection() {
       if (get_config()->backend_tls_sni_name) {
         sni_name = get_config()->backend_tls_sni_name.get();
       } else {
-        sni_name = get_config()->downstream_addrs[0].host.get();
+        sni_name = downstream_addr.host.get();
       }
 
       if (sni_name && !util::numeric_host(sni_name)) {
@@ -307,16 +327,15 @@ int Http2Session::initiate_connection() {
         assert(conn_.fd == -1);
 
         conn_.fd = util::create_nonblock_socket(
-            get_config()->downstream_addrs[0].addr.storage.ss_family);
+            downstream_addr.addr.storage.ss_family);
         if (conn_.fd == -1) {
           return -1;
         }
 
-        rv = connect(
-            conn_.fd,
-            // TODO maybe not thread-safe?
-            const_cast<sockaddr *>(&get_config()->downstream_addrs[0].addr.sa),
-            get_config()->downstream_addrs[0].addrlen);
+        rv = connect(conn_.fd,
+                     // TODO maybe not thread-safe?
+                     const_cast<sockaddr *>(&downstream_addr.addr.sa),
+                     downstream_addr.addrlen);
         if (rv != 0 && errno != EINPROGRESS) {
           return -1;
         }
@@ -336,15 +355,14 @@ int Http2Session::initiate_connection() {
         assert(conn_.fd == -1);
 
         conn_.fd = util::create_nonblock_socket(
-            get_config()->downstream_addrs[0].addr.storage.ss_family);
+            downstream_addr.addr.storage.ss_family);
 
         if (conn_.fd == -1) {
           return -1;
         }
 
-        rv = connect(conn_.fd, const_cast<sockaddr *>(
-                                   &get_config()->downstream_addrs[0].addr.sa),
-                     get_config()->downstream_addrs[0].addrlen);
+        rv = connect(conn_.fd, const_cast<sockaddr *>(&downstream_addr.addr.sa),
+                     downstream_addr.addrlen);
         if (rv != 0 && errno != EINPROGRESS) {
           return -1;
         }
@@ -469,10 +487,12 @@ int Http2Session::downstream_connect_proxy() {
   if (LOG_ENABLED(INFO)) {
     SSLOG(INFO, this) << "Connected to the proxy";
   }
+  auto &downstream_addr = get_config()->downstream_addrs[addr_idx_];
+
   std::string req = "CONNECT ";
-  req += get_config()->downstream_addrs[0].hostport.get();
+  req += downstream_addr.hostport.get();
   req += " HTTP/1.1\r\nHost: ";
-  req += get_config()->downstream_addrs[0].host.get();
+  req += downstream_addr.host.get();
   req += "\r\n";
   if (get_config()->downstream_http_proxy_userinfo) {
     req += "Proxy-Authorization: Basic ";
@@ -1694,4 +1714,6 @@ bool Http2Session::should_hard_fail() const {
   }
 }
 
+size_t Http2Session::get_addr_idx() const { return addr_idx_; }
+
 } // namespace shrpx

src/shrpx_http2_session.h

@@ -46,6 +46,7 @@ using namespace nghttp2;
 namespace shrpx {
 
 class Http2DownstreamConnection;
+class Worker;
 
 struct StreamData {
   Http2DownstreamConnection *dconn;
@@ -53,7 +54,7 @@ struct StreamData {
 
 class Http2Session {
 public:
-  Http2Session(struct ev_loop *loop, SSL_CTX *ssl_ctx);
+  Http2Session(struct ev_loop *loop, SSL_CTX *ssl_ctx, Worker *worker);
   ~Http2Session();
 
   int check_cert();
@@ -143,6 +144,8 @@ public:
 
   void submit_pending_requests();
 
+  size_t get_addr_idx() const;
+
   enum {
     // Disconnected
     DISCONNECTED,
@@ -188,11 +191,14 @@ private:
   std::function<int(Http2Session &)> on_read_, on_write_;
   // Used to parse the response from HTTP proxy
   std::unique_ptr<http_parser> proxy_htp_;
+  Worker *worker_;
   // NULL if no TLS is configured
   SSL_CTX *ssl_ctx_;
   nghttp2_session *session_;
   const uint8_t *data_pending_;
   size_t data_pendinglen_;
+  // index of get_config()->downstream_addrs this object uses
+  size_t addr_idx_;
   int state_;
   int connection_check_state_;
   bool flow_control_;

src/shrpx_worker.cc

@@ -59,7 +59,7 @@ Worker::Worker(struct ev_loop *loop, SSL_CTX *sv_ssl_ctx, SSL_CTX *cl_ssl_ctx,
   ev_async_start(loop_, &w_);
 
   if (get_config()->downstream_proto == PROTO_HTTP2) {
-    http2session_ = make_unique<Http2Session>(loop_, cl_ssl_ctx_);
+    http2session_ = make_unique<Http2Session>(loop_, cl_ssl_ctx, this);
   } else {
     http1_connect_blocker_ = make_unique<ConnectBlocker>(loop_);
   }
@@ -197,6 +197,8 @@ struct ev_loop *Worker::get_loop() const {
 
 SSL_CTX *Worker::get_sv_ssl_ctx() const { return sv_ssl_ctx_; }
 
+SSL_CTX *Worker::get_cl_ssl_ctx() const { return cl_ssl_ctx_; }
+
 void Worker::set_graceful_shutdown(bool f) { graceful_shutdown_ = f; }
 
 bool Worker::get_graceful_shutdown() const { return graceful_shutdown_; }

src/shrpx_worker.h

@@ -98,6 +98,7 @@ public:
   ConnectBlocker *get_http1_connect_blocker() const;
   struct ev_loop *get_loop() const;
   SSL_CTX *get_sv_ssl_ctx() const;
+  SSL_CTX *get_cl_ssl_ctx() const;
 
   void set_graceful_shutdown(bool f);
   bool get_graceful_shutdown() const;