nginx 502 bad gateway

后来原来的错误消失了，又出现了新的错误。上游超时超时？

server {

listen 80;

server_name *.xywy.com ; large_client_header_buffers 4 16k; client_max_body_size 300m; client_body_buffer_size 128k; proxy_connect_timeout 600; proxy_read_timeout 600; proxy_send_timeout 600; proxy_buffer_size 64k; proxy_buffers 4 32k; proxy_busy_buffers_size 64k;