NGINX + HHVM + SOAP Chunked响应

Question

似乎NGINX不会将正确的HTTP协议传递给HHVM后端。

这里我做过的测试：

如果客户端发送HTTP / 1.1请求（非分块），NGINX会将其传递给HHVM后端，并且正确的响应将返回给客户端

(client)                           (server backend)
HTTP/1.1(non chunked)  -> NGINX ->    HHVM
                                       |
                                       v
(HTTP/1.1 200)         <- NGINX <- (non chunked response)

如果客户端发送HTTP / 1.1请求（chuncked），则服务器会产生分块响应，但NGINX会触发此日志消息

upstream prematurely closed connection while reading response header from upstream, request: "POST /soap HTTP/1.1", upstream: "fastcgi://unix:/var/run/hhvm/sock:"

并返回502（错误网关）响应

(client)                           (server backend)
HTTP/1.1(chunked)      -> NGINX ->    HHVM
                                       |
                                       v
(HTTP/1.1 502)         <- NGINX <- (chunked response)

为什么我使用分块响应从NGINX获得502？

hhvm / fastcgi / hhvm config有什么问题吗？

我仔细检查后端给出了正确的1/1响应:(

我的情景是：

NGINX:nginx/1.4.6 (Ubuntu)
HHVM: HipHop VM 3.6.1 (rel)

NGINX配置

server {
   listen      80;
   server_name xxxxx;

   root /usr/share/nginx/web;
   include hhvm.conf;


   location / {
       # try to serve file directly, fallback to rewrite
       try_files $uri @rewriteapp;
   }

   location @rewriteapp {
       # rewrite all to app.php
       rewrite ^(.*)$ /app.php/$1 last;
   }

   location ~ ^/(app|app_dev|app_benchmark|app_logall|config)\.php(/|$) {
       fastcgi_keep_conn on;
       #fastcgi_pass   127.0.0.1:9000;
       fastcgi_pass   unix:/var/run/hhvm/sock;
       fastcgi_index  index.php;
       fastcgi_param  SCRIPT_FILENAME $document_root$fastcgi_script_name;

       fastcgi_buffer_size 128k;
       fastcgi_buffers 256 16k;
       fastcgi_busy_buffers_size 256k;
       fastcgi_temp_file_write_size 256k;
       fastcgi_read_timeout 240;
       fastcgi_intercept_errors on;

       include        fastcgi_params;

   }
}