Integrated Search/How to write a custom crawler

From TeamWeaverWiki

Current revision as of 07:46, 29 April 2010

This short guide describes how to write crawlers to make additional data sources available for searching with TeamWeaver Integrated Search.

A list of existing crawlers can be found at: supported data sources resp. repo_config.xml.

Note that for most web-based sources, the generic web crawler can be sufficient for a first shot solution. However, the web crawler does index complete HTML files and might thus result in a lower search quality (e.g. due to indexing navigation menues etc.).

Pull vs. Push Crawlers

There are two general strategies for crawling data sources with TeamWeaverIS:

• "Pull"-Crawlers are implemented/deployed within TeamWeaverIS and allow to crawl/extract data by accessing external sources/system. Pull-crawlers are fairly easy to realize, but have the disadvantage, that the index might not be accurate, since TeamWeaverIS does only learn about data changes when a crawl is executed. Typically, there is a script file to update the TeamWeaverIS index regularly (e.g. every night). Index accuracy thus depends on the frequency of crawls.
• "Push"-Crawlers are implemented on the side of the client system which includes the data to be indexed. They proactively update the index and thus need to have a direct (network) connection to the TeamWeaverIS backend. Accordingly, push-crawlers are more difficult to implement, but can reflect changes in the data more rapidly in the index.

Writing a "Pull"-Crawler

At the basic level, creating a pull-crawler requires to implement two Java classes and changing two XML-files - a Crawler and a Processor each. Crawlers are classes which access a data source and extract/create single data items. Processors act upon these items to prepare them for feeding into the index.

Crawler

• You need to create a subclass of CrawlerBase which basically means to implement a method crawlObject. See our JIRACrawler for an example.
• Afterwards, register your new crawler in defaultCrawlers.xml. You need to define a unique <repoType> key, which corresponds to the <srcType> in repo_config.xml.

Processor

• You need to create a subclass of ProcessorBase. See our JIRAProcessor as an example.
• Afterwards, register your new processor in defaults.xml by wiring it with the corresponding crawler.

Advanced topics

• tbd. (generic JDBC crawler, Plain index vs. metadata)

Writing a "Push"-Crawler

• tbd.
• Push-Crawlers have to call the TeamWeaver backend's IndexService
• You might want to look at our Woogle4MediaWiki code for an example implementation of a push-crawler. The particular place to look at is the "WoogleRemote" addon [1].