Page: http://wiki.cocoondev.org/Wiki.jsp?page=WritingPipelineComponents , version: 4 on Wed May 14 16:33:03 2003 by SylvainWallez
- * __[Writing components for maximum cache efficiency|WritingForCacheEfficiency]__ + * __[Writing efficient cacheable pipeline components|WritingForCacheEfficiency]__ Page: http://wiki.cocoondev.org/Wiki.jsp?page=WritingForCacheEfficiency , version: 2 on Wed May 14 16:32:11 2003 by SylvainWallez + There are a number of existing Cocoon components that implement this interface and that you can take as samples when writing your own. + + However, here are a few tips that can help to achieve maximum efficiency. + + ---- + !!Avoiding uncessary operations + - However, achieving maximum performance to deliver cached content needs some careful coding. ? ^^^^^^^^^^ + Achieving maximum performance to deliver cached content needs some careful coding of cacheable components. ? ^ ++++++++++++++++++++++++ - Here's a reminder of the various steps that occur when handling a request :\\ ? -- + Here's a reminder of the various steps that occur when handling a request : - __1__ - the sitemap is executed, meaning we create a pipeline object, and pipeline components : generator, transformers, and serializer.\\ ? ^^^^^^^ -- + # the sitemap is executed, meaning we create a pipeline object, and pipeline components : generator, transformers, and serializer. ? ^ - __2__ - the {{setup()}} method of all pipeline components is called (except serializer which doesn't have one)\\ ? ^^^^^^^ -- + # the {{setup()}} method of all pipeline components is called (except serializer which doesn't have one) ? ^ - __3__ - the {{getKey()}} method of all pipeline components is called - - Knowing the key, the pipeline can get the associated cache entry and its validity. If the cache validity either is invalid or needs a fresh validity object to be compared with, then :\\ + # the {{getKey()}} method of all pipeline components is called\\ \\Knowing the key, the pipeline can get the associated cache entry and its validity. If the cache validity either is invalid or needs a fresh validity object to be compared with, then :\\. ? +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ + - __4__ - the {{getValidity()}} method of all pipeline components is called - - The pipeline can then know if the cache entry is valid. If it's valid, it delivers the cached content. If it's invalid, then :\\ + # the {{getValidity()}} method of all pipeline components is called\\ \\The pipeline can then know if the cache entry is valid. If it's valid, it delivers the cached content. If it's invalid, then :\\. ? ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ + - __5__ - the pipeline is connected. This means {{setXMLConsumer()}} is called on transformers and {{setOutputStream()}} is called on the serializer\\ ? ^^^^^^^ -- + # the pipeline is connected. This means {{setXMLConsumer()}} is called on transformers and {{setOutputStream()}} is called on the serializer ? ^ - __6__ - the generator's {{generate()}} method is called, and starts the SAX stream processing, resulting first in {{startDocument()}} being called on transformers and serializer. ? ^^^^^^^ + # the generator's {{generate()}} method is called, and starts the SAX stream processing, resulting first in {{startDocument()}} being called on transformers and serializer. ? ^ + ---- + !! Cache validity depends on pipeline execution + + Some pipeline components have a validity that depends on the execution of the pipeline. Some examples include : + * the DirectoryGenerator : validity is the list of files whose XML representation is produced, + * the TraxTransformer : we need to track source included with the {{document()}} function. + + How can such components be made cacheable, since {{getValidity()}} is called before pipeline execution (see above) ? + + The solution used in the DirectoryGenerator is for {{getValidity()}} to return a validity object that is initially just an empty placeholder, and is filled with file names and modification dates during the pipeline execution phase. When pipeline execution is finished, the produced content goes into the cache with a validity object which is correctly filled. + + Et voilà ! Cache validity is actually computed during pipeline execution ! + ----
