后端技术 by Tim Yang

Twitter的平台总监Ryan Sarver在最近一封给开发者公开email Platform announcements from LeWeb提到，打算将API用户请求限制扩大10倍，由目前的150次/小时扩大到1,500次/小时(但同时将搜索范围缩短到7天)。

*Auth announcements*
With the recent launches of Retweet, Lists and Geotagging we have seen
applications struggle to provide the experience they want for their users
within the 150 req/hr limit. We are excited to open the skies up a bit and
provide some more room for developers to work within. Starting in a few
weeks all OAuth requests to api.twitter.com/1/ will be able to take
advantage of a 10x rate limit increase. Basic Whitelisting still exists and
is unchanged. We look forward to what this means in terms of the increased
richness around the user experience in Twitter apps.

注意文中的限制是OAuth客户端，为什么只限OAuth客户端？由于OAuth客户端可控性较强。如果发现app有滥用api嫌疑，可以直接suspend这个app；而另外一种鉴权方式Basic Authentication方式并不强制client传递app id, 服务器判断app abuse较困难。

在我的理解，microblog的最大的特性应该是realtime,(另外一特性应是social graph), 即使Twitter扩大rate limit, REST方式的HTTP协议终究没法实现realtime，如果所有的客户端都1分钟请求25次(1,500/60=25)，twitter服务器稳定性一向声誉不佳，增大后能否经住考验也是一个疑问。

如果要实现真正的realtime, 目前有http callback或者XMPP等方案。callback由于客户端通常在防火墙内并不可行。XMPP由于协议栈庞大，服务端及客户端编写都比较繁琐，而且XMPP是为IM协议设计，所以并不十分适合twitter api。

另外Twitter在邮件中还提到，打算将所有最新更新feed的数据流(Twitter称为Firehose)向所有人开放。

*Firehose for everyone*
Finally, the announcement that has garnered the most coverage and
excitement. As I stated in the session at LeWeb we are committed to
providing a framework for any company big or small, rich or poor to do a
deal with us to get access to the Firehose in the same way we did deals with
Google and Microsoft. We want everyone to have the opportunity — terms will
vary based on a number of variables but we want a two-person startup in a
garage to have the same opportunity to build great things with the full feed
that someone with a billion dollar market cap does. There are still a lot of
details to be fleshed out and communicated, but this a top priority for us
and we look forward to what types of companies and products get built on top
of this unique and rich stream.

Firehose可以理解成所有Twitter最近更新的水龙头，目前只对 Microsoft, Google等少量公司开放。Twitter表示以后即使”a two-person startup in a garage”这样的公司也可以获取firehose访问权限, “We want everyone to have the opportunity”。相信不少公司将会为这一特性而激动甚至疯狂。firehose开放意味为第三方提供了无限的创意空间，另外它也会对Twitter已有的服务search, geotag等业务构成威胁，走出这一步需要很大的勇气。

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