Nginx不更新最大年龄

如果我向configuration为caching上游的Nginx代理服务器发出请求，我会得到以下响应头文件：

{'content-length': '13200000', 'x-cache-status': 'MISS', 'server': 'nginx/1.9.9', 'connection': 'keep-alive', 'cache-control': 'max-age=45', 'date': 'Fri, 27 Jan 2017 10:57:55 GMT'} 

几秒钟后，我再次做同样的请求，我得到以下标题：

 {'content-length': '13200000', 'x-cache-status': 'HIT', 'server': 'nginx/1.9.9', 'connection': 'keep-alive', 'cache-control': 'max-age=45', 'date': 'Fri, 27 Jan 2017 10:58:18 GMT'} 

上游服务器指定max-age头为45秒，第二个响应头是否有更新的max-age头？ 这是最大年龄= 45-（请求之间的时间）？

编辑

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重现行为的示例configuration：

 http { include mime.types; default_type application/octet-stream; upstream backend { server localhost:8080; } proxy_cache_path /etc/nginx/wwwroot/cache levels=1:2 keys_zone=my_cache:10m max_size=10g inactive=60m use_temp_path=off; server { listen 80; location / { proxy_pass http://backend; proxy_cache my_cache; add_header X-Cache-Status $upstream_cache_status; } } server { listen 8080; root /etc/nginx/wwwroot; expires 60s; } } 

结果：

 root@ubuntu:/home/parallels# curl -I localhost/testfile.txt HTTP/1.1 200 OK Server: nginx/1.10.0 (Ubuntu) Date: Sat, 28 Jan 2017 19:08:45 GMT Content-Type: text/plain Content-Length: 12 Connection: keep-alive Last-Modified: Fri, 27 Jan 2017 14:45:39 GMT ETag: "588b5d13-c" Expires: Sat, 28 Jan 2017 19:09:45 GMT Cache-Control: max-age=60 X-Cache-Status: MISS Accept-Ranges: bytes root@ubuntu:/home/parallels# curl -I localhost/testfile.txt HTTP/1.1 200 OK Server: nginx/1.10.0 (Ubuntu) Date: Sat, 28 Jan 2017 19:08:48 GMT Content-Type: text/plain Content-Length: 12 Connection: keep-alive Last-Modified: Fri, 27 Jan 2017 14:45:39 GMT ETag: "588b5d13-c" Expires: Sat, 28 Jan 2017 19:09:45 GMT Cache-Control: max-age=60 X-Cache-Status: HIT Accept-Ranges: bytes