Yahoo Weather API 上的服务器端缓存？

Question

雅虎天气 API 似乎有一个错误，每次我发送请求时都会得到相同的天气。有趣的设计是，响应中没有任何时间戳字段来识别天气时间。

$ curl "http://weather.yahooapis.com/forecastjson?p=CHXX0099&u=c" -v
* About to connect() to weather.yahooapis.com port 80 (#0)
*   Trying 180.233.115.34... connected
* Connected to weather.yahooapis.com (180.233.115.34) port 80 (#0)
> GET /forecastjson?p=CHXX0099&u=c HTTP/1.1
> User-Agent: curl/7.21.3 (i386-redhat-linux-gnu) libcurl/7.21.3 NSS/3.12.9.0 zlib/1.2.5 libidn/1.19 libssh2/1.2.7
> Host: weather.yahooapis.com
> Accept: */*
> 
< HTTP/1.1 200 OK
< Date: Tue, 31 May 2011 12:58:10 GMT
< Cache-Control: private, max-age=1200
< Expires: Tue, 31 May 2011 13:18:10 GMT
< Connection: close
< Transfer-Encoding: chunked
< Content-Type: application/json;charset=UTF-8
< 
* Closing connection #0
{"units":{"temperature":"C","speed":"km\/h","distance":"km","pressure":"mb"},"location":{"location_id":"CHXX0099","city":"Nanjing","state_abbreviation":"JI","country_abbreviation":"CH","elevation":3,"latitude":32,"longitude":118.80000000000000},"wind":{"speed":6.00000000000000,"direction":"N"},"atmosphere":{"humidity":"22","visibility":12.01000000000000,"pressure":1024.00000000000000,"rising":""},"url":"http:\/\/weather.yahoo.com\/forecast\/CHXX0099.html","logo":"http:\/\/l.yimg.com\/a\/i\/us\/nt\/ma\/ma_nws-we_1.gif","astronomy":{"sunrise":"06:22","sunset":"18:09"},"condition":{"text":"Sunny","code":"32","image":"http:\/\/l.yimg.com\/a\/i\/us\/we\/52\/32.gif","temperature":14.00000000000000},"forecast":[{"day":"Today","condition":"Mostly Clear","high_temperature":13.00000000000000,"low_temperature":3.00000000000000},{"day":"Tomorrow","condition":"Partly Cloudy","high_temperature":16.00000000000000,"low_temperature":5.00000000000000}]}

但是，如果我通过VPN请求相同的接口，返回的数据正好。

$ curl "http://weather.yahooapis.com/forecastjson?p=CHXX0099&u=c" -v
* About to connect() to weather.yahooapis.com port 80 (#0)
*   Trying 180.233.115.34... connected
* Connected to weather.yahooapis.com (180.233.115.34) port 80 (#0)
> GET /forecastjson?p=CHXX0099&u=c HTTP/1.1
> User-Agent: curl/7.21.3 (i386-redhat-linux-gnu) libcurl/7.21.3 NSS/3.12.9.0 zlib/1.2.5 libidn/1.19 libssh2/1.2.7
> Host: weather.yahooapis.com
> Accept: */*
> 
< HTTP/1.1 200 OK
< Date: Tue, 31 May 2011 12:58:10 GMT
< Cache-Control: private, max-age=1200
< Expires: Tue, 31 May 2011 13:18:10 GMT
< Connection: close
< Transfer-Encoding: chunked
< Content-Type: application/json;charset=UTF-8
< 
* Closing connection #0
{"units":{"temperature":"C","speed":"km\/h","distance":"km","pressure":"mb"},"location":{"location_id":"CHXX0099","city":"Nanjing","state_abbreviation":"JI","country_abbreviation":"CH","elevation":3,"latitude":32,"longitude":118.80000000000000},"wind":{"speed":6.00000000000000,"direction":"N"},"atmosphere":{"humidity":"22","visibility":12.01000000000000,"pressure":1024.00000000000000,"rising":""},"url":"http:\/\/weather.yahoo.com\/forecast\/CHXX0099.html","logo":"http:\/\/l.yimg.com\/a\/i\/us\/nt\/ma\/ma_nws-we_1.gif","astronomy":{"sunrise":"06:22","sunset":"18:09"},"condition":{"text":"Sunny","code":"32","image":"http:\/\/l.yimg.com\/a\/i\/us\/we\/52\/32.gif","temperature":14.00000000000000},"forecast":[{"day":"Today","condition":"Mostly Clear","high_temperature":13.00000000000000,"low_temperature":3.00000000000000},{"day":"Tomorrow","condition":"Partly Cloudy","high_temperature":16.00000000000000,"low_temperature":5.00000000000000}]}

就个人而言，我认为这与 Varnish 或 Squid 的东西有关。你是否也受到这个问题的影响？在我找到官方支持链接之前，我该怎么做才能使服务器端缓存过期？

Answer 1

我不完全确定它是否在这里同样适用，但 IE 对 GET 请求的积极缓存的一个常见解决方案是在请求中添加时间戳参数 - 因为每次发出请求时值都会改变，每个请求看起来都是唯一的.

选择一个不太可能与 API 参数冲突的参数名称，并将其设置为每次发出请求时的当前时间，看看是否能解决问题。

Answer 2

在您发布的问题中，两个 Curl 示例看起来相同，但我想您注意到返回的数据因您的网络路径而异。

这些 JSON 响应有一定程度的缓存（我相信是 30 分钟），但您的网络上可能还有额外的缓存。

一个重要的问题是后端的天气预报数据会定期更新，因为预报本身并不会那么频繁地变化。

其实你使用的JSON天气接口并没有官方支持，但我相信它只是雅虎自己在各个页面上使用的。

“官方”支持的接口请参考Yahoo! Weather page on YDN。这个接口本身并没有那么有用，因为它只是 XML 格式。相反，您可以使用 YQL console 传递您的位置并接收返回 JSON 格式的数据。

例如，试试这个查询：select * from weather.bylocation where location="Nanjing, CN"。在结果中，请注意 lastBuildData 值，它是预测的最后一次更新：

{
 "query": {
  "count": 1,
  "created": "2011-12-30T20:03:17Z",
  "lang": "en-US",
  "results": {
   "weather": {
    "rss": {
     "version": "2.0",
     "geo": "http://www.w3.org/2003/01/geo/wgs84_pos#",
     "yweather": "http://xml.weather.yahoo.com/ns/rss/1.0",
     "channel": {
      "title": "Yahoo! Weather - Nanjing, CN",
      "link": "http://us.rd.yahoo.com/dailynews/rss/weather/Nanjing__CN/*http://weather.yahoo.com/forecast/CHXX0099_f.html",
      "description": "Yahoo! Weather for Nanjing, CN",
      "language": "en-us",
      "lastBuildDate": "Sat, 31 Dec 2011 3:00 am CST",
      "ttl": "60",
      "location": {
       "city": "Nanjing",
       "country": "China",
       "region": ""
      },
      "units": {
       "distance": "mi",
       "pressure": "in",
       "speed": "mph",
       "temperature": "F"
      },
      "wind": {
       "chill": "25",
       "direction": "90",
       "speed": "4"
      },
      "atmosphere": {
       "humidity": "83",
       "pressure": "30.45",
       "rising": "2",
       "visibility": "0.99"
      },
      "astronomy": {
       "sunrise": "7:03 am",
       "sunset": "5:09 pm"
      },
      "image": {
       "title": "Yahoo! Weather",
       "width": "142",
       "height": "18",
       "link": "http://weather.yahoo.com",
       "url": "http://l.yimg.com/a/i/brand/purplelogo//uh/us/news-wea.gif"
      },
      "item": {
       "title": "Conditions for Nanjing, CN at 3:00 am CST",
       "lat": "32.05",
       "long": "118.78",
       "link": "http://us.rd.yahoo.com/dailynews/rss/weather/Nanjing__CN/*http://weather.yahoo.com/forecast/CHXX0099_f.html",
       "pubDate": "Sat, 31 Dec 2011 3:00 am CST",
       "condition": {
        "code": "20",
        "date": "Sat, 31 Dec 2011 3:00 am CST",
        "temp": "30",
        "text": "Fog"
       },
       "description": "
\nCurrent Conditions:
\nFog, 30 F
\n
Forecast:
\nSat - Sunny. High: 50 Low: 28
\nSun - Sunny. High: 51 Low: 28
\n
\nFull Forecast at Yahoo! Weather

\n(provided by The Weather Channel)
",
       "forecast": [
        {
         "code": "32",
         "date": "31 Dec 2011",
         "day": "Sat",
         "high": "50",
         "low": "28",
         "text": "Sunny"
        },
        {
         "code": "32",
         "date": "1 Jan 2012",
         "day": "Sun",
         "high": "51",
         "low": "28",
         "text": "Sunny"
        }
       ],
       "guid": {
        "isPermaLink": "false",
        "content": "CHXX0099_2012_01_01_7_00_CST"
       }
      }
     }
    }
   }
  }
 }
}