Add server_request_body_incomplete flag to track incomplete body transfers

Author: JakeChampion

include/proxy/http/HttpSM.h

@@ -512,6 +512,7 @@ class HttpSM : public Continuation, public PluginUserArgs<TS_USER_ARGS_TXN>
   int     server_connection_provided_cert = 0;
   int64_t client_request_body_bytes       = 0;
   int64_t server_request_body_bytes       = 0;
+  bool    server_request_body_incomplete  = false;
   int64_t server_response_body_bytes      = 0;
   int64_t client_response_body_bytes      = 0;
   int64_t cache_response_body_bytes       = 0;

src/proxy/http/HttpSM.cc

@@ -2072,11 +2072,14 @@ HttpSM::state_read_server_response_header(int event, void *data)
     if (tunnel.is_tunnel_alive()) {
       // Record bytes already written to the server before aborting the tunnel.
       // tunnel_handler_post_server() won't be called after abort, so we must
-      // capture this here to prevent the connection from being pooled later.
+      // capture this here for stats/logging purposes.
       HttpTunnelConsumer *server_consumer = tunnel.get_consumer(server_txn);
       if (server_consumer && server_request_body_bytes == 0) {
         server_request_body_bytes = server_consumer->bytes_written;
       }
+      // Mark the body transfer as incomplete so the origin connection is not
+      // pooled. The origin may have unconsumed body data in the TCP stream.
+      server_request_body_incomplete = true;
       tunnel.abort_tunnel();
       // Make sure client connection is closed when we are done in case there is cruft left over
       t_state.client_info.keep_alive = HTTPKeepAlive::NO_KEEPALIVE;