gae crawler

Objectify-Appengine 或 Objectify 是一个 ORM 类的库，它简化 Bigtable 以及 GAE 中的数据持久性。作为一个映射层，Objectify 通过一个简洁的 API 将自身插入到 POJOs 与 Google 的重型设备之间。您可以使用一个熟悉的 JPA 注释子集（尽管 Objectify 不实现完整的规范）以及少量生命周期注释，来存留和检索 Java 对象形式的数据。从本质上讲，Objectify 是为 Google 的 Bigtable 明确设计的一个轻量级 Hibernate。

Objectify 与 Hibernate 的类似之处在于，它允许您针对 Bigtable 映射和利用 POJOs，您将这个看作是 GAE 中的一个抽象。除了 JPA 注释的子集之外，Objectify 运用其自己的注释，这体现了 GAE 数据存储的独特功能。Objectify 还允许关系，显示一个查询界面来支持 GAE 筛选和排序概念。

Apache Droids
droids-crawler
https://cwiki.apache.org/DROIDS/droids-crawler.html
http://code.google.com/p/gwt-platform/
http://code.google.com/p/gwt-platform/source/browse/#hg%2Fgwtp-samples%2Fgwtp-sample-crawler-service

Web crawlers and Google App Engine Hosted applications

up vote 1 down vote favorite 2	Is it impossible to run a web crawler on GAE along side with my app considering the I am running the free startup version? python google-app-engine web-crawler link | edit | flag edited Mar 25 '09 at 12:26 myroslav 987 2 11 asked Mar 24 '09 at 7:44 Spikie 107 1 11 50% accept rate

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While Google hadn't exposed scheduling, queue and background tasks API, you can do any processing only as an answer to external HTTP request. You'd need some heartbeat service that will process one item from crawler's queue at a time (not to hit GAE limits). To do crawling from GAE, you have to split your application into queue (that stores queue data in Datastore), queue processor that will react to external HTTP heartbeat and your actual crawling logic. You'd manually have to watch your quota usage and start heartbeat when you have spare quota, and stop if it is used up. When Google introduces the APIs I've told in the beginning you'd have to rewrite parts that are implemented more effectively via Google API. UPDATE: Google introduced Task Queue API some time ago. See task queue docs for python and java. link | edit | flag edited Apr 29 '10 at 11:37 answered Mar 25 '09 at 12:26 myroslav 987 2 11

up vote 1 down vote	App Engine code only runs in response to HTTP requests, so you can't run a persistent crawler in the background. With the upcoming release of scheduled tasks, you could write a crawler that uses that functionality, but it would be less than ideal. link | edit | flag answered Mar 24 '09 at 12:17 Nick Johnson 41.1k 4 27 65

up vote 0 down vote	I suppose you can (i.e., it's not impossible to) run it, but it will be slow and you'll run into limits quite quickly. As CPU quotas are going to be decreased at the end of May even further, I'd recommend against it. link | edit | flag edited Mar 24 '09 at 10:26 answered Mar 24 '09 at 10:14 SilentGhost 40k 6 41 98

up vote 0 down vote	It's possible. But that's not really an application for appengine just as Arachnid wrote. If you manage to get it working I'll doubt you'll stay in the qotas for free accounts. link | edit | flag answered Mar 24 '09 at 13:11 Vasil 5,272 4 21 48

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