使用 Ajax/jQuery 从 CouchDB 读取连续源

发布于 2024-10-03 03:33:24 字数 689 浏览 0 评论 0原文

我想使用 jQuery 监听 CouchDB 的连续更改 - 现在可以工作了：

http://localhost:5984/testdb/_changes?feed=continuous

这意味着每次有数据库更新时我都会得到一个新的 json 行 - 但如何使用 jQuery 读取此 URL 的更新？

我尝试使用这个，但它不起作用：

$.ajax(
{
  url : "http://localhost:5984/testdb/_changes?feed=continuous&callback=?",
  dataType : 'json',
  success : function(data)
  {
    alert(data.results.length);
  }
});

编辑：$ .ajax调用“成功”函数并立即返回，它不会“轮询”更改..（ajax列的时间线列下图中是 16ms)

alt text

不，这不是跨域 ajax 问题 - 我可以在fireBug 有一个包含正确数量元素的响应

所以任何指导/建议将不胜感激 - 它不一定是 jQuery - 普通的旧 javscript 也可以

原文

I want to listen for continuous changes from CouchDB using jQuery - now this works:

http://localhost:5984/testdb/_changes?feed=continuous

which means that I get a new line of json every time there is a db update - but how do I read updates off this URL using jQuery?

I tried using this but it doesn't work:

$.ajax(
{
  url : "http://localhost:5984/testdb/_changes?feed=continuous&callback=?",
  dataType : 'json',
  success : function(data)
  {
    alert(data.results.length);
  }
});

Edit: $.ajax calls the "success" function and returns immediately, it doesn't "poll" for changes.. (timeline column for ajax column in image below is 16ms)

alt text

And no, it isn't a cross-domain ajax problem - I can see in fireBug there is a response with the right number of elements

So any guidance/advice would be appreciated - it doesn't have to be jQuery - plain old javscript would do as well

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毁虫ゝ 2024-10-10 03:33:25

正如 Gjorgji Tashkovski 提到的 feed=continuous 适用于服务器端，您可以使用feed=longpoll 适合您的用例。

(function($) {
  // this is a recursive function
  function longpoll(database, last_seq) {
    var url = "/" + database + "/_changes?feed=longpoll";
    // If we don't have a sequence number, then see where we are up to.
    if (last_seq) {
      url = url + "&since=" + last_seq;
    }
    $.ajax({
      type: "GET",
      url: url,
      dataType: 'json',
      success: function(data) {
        // Now we need to see what to do with the data.
        console.log(document.data.results);

        // And set up the re-run of the fetch query.
        // recursive call
        longpoll(database, data.last_seq);
      }
    })
  }
  
  $.couch.longpoll = longpoll;
}(jQuery));

此示例源代码来自现已存档的博客：
https://web.archive.org/web/20170821130003/http://schinckel.net/2012/01/22/jquery-long-poll-for-couchdb-changes./

As Gjorgji Tashkovski mentioned feed=continuous is intended for server-side, you can use feed=longpoll for your use case.

(function($) {
  // this is a recursive function
  function longpoll(database, last_seq) {
    var url = "/" + database + "/_changes?feed=longpoll";
    // If we don't have a sequence number, then see where we are up to.
    if (last_seq) {
      url = url + "&since=" + last_seq;
    }
    $.ajax({
      type: "GET",
      url: url,
      dataType: 'json',
      success: function(data) {
        // Now we need to see what to do with the data.
        console.log(document.data.results);

        // And set up the re-run of the fetch query.
        // recursive call
        longpoll(database, data.last_seq);
      }
    })
  }
  
  $.couch.longpoll = longpoll;
}(jQuery));

This example source code came from this now archived blog:
https://web.archive.org/web/20170821130003/http://schinckel.net/2012/01/22/jquery-long-poll-for-couchdb-changes./

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不再让梦枯萎 2024-10-10 03:33:24

我立即想到了两种好方法来做到这一点。

使用计时器（即 setTimeout();），每 X 秒对更改源运行 AJAX 调用。您还将存储您收到的最后一个序列号，以便您可以告诉更改源在下次轮询时启动哪个序列号。这将防止重复数据并使响应更小。
根据您需要支持的浏览器，您也许可以使用 EventSource API。这是一个 jQuery 实现： https://github.com/rwldrn/jquery.eventsource