Package com.yahoo.search.searchers

Class CacheControlSearcher

  • All Implemented Interfaces:
    com.yahoo.component.Component, com.yahoo.component.Deconstructable, Comparable<com.yahoo.component.Component>
    public class CacheControlSearcher
extends Searcher
    Searcher that sets cache control HTTP headers in response based on query/GET parameters to control caching done by proxy/caches such as YSquid and YTS:
    • max-age=XXX - set with &cachecontrol.maxage parameter
    • stale-while-revalidate=YYY - set with &cachecontrol.staleage
    • no-cache - if Vespa &noCache or &cachecontrol.nocache parameter is set to true

    This is controlled through the three query parameters cachecontrol.maxage, cachecontrol.staleage and cachecontrol.nocache, with the obvious meanings.

    Example:
    • Request: "?query=foo&cachecontrol.maxage=60&cachecontrol.staleage=3600"
    • Response HTTP header: "Cache-Control: max-age=60, revalidate-while-stale=3600"
    Further documentation on use of Cache-Control headers: http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.9
    Author:
    Frode Lundgren

    • Constructor Detail

      • CacheControlSearcher

        public CacheControlSearcher()

    • Method Detail

      • search

        public Result search​(Query query,
                     Execution execution)
        Description copied from class: Searcher
        Override this to implement your searcher.

        Searcher implementation subclasses will, depending on their type of logic, do one of the following:

        • Query processors: Access the query, then call execution.search and return the result
        • Result processors: Call execution.search to get the result, access it and return
        • Sources (which produces results): Create a result, add the desired hits and return it.
        • Federators (which forwards the search to multiple subchains): Call search on the desired subchains in parallel and get the results. Combine the results to one and return it.
        • Workflows: Call execution.search as many times as desired, using different queries. Eventually return a result.

        Hits come in two kinds - concrete hits are actual content of the kind requested by the user, meta hits are hits which provides information about the collection of hits, on the query, the service and so on.

        The query specifies a window into a larger result list that must be returned from the searcher through hits and offset; Searchers which returns list of hits in the top level in the result must return at least hits number of hits (or if impossible; all that are available), starting at the given offset. In addition, searchers are allowed to return any number of meta hits (although this number is expected to be low). For hits contained in nested hit groups, the concept of a window defined by hits and offset is not well defined and does not apply.

        Error handling in searchers:

        • Unexpected events: Throw any RuntimeException. This query will fail with the exception message, and the error will be logged
        • Expected events: Create (new Result(Query, ErrorMessage) or add result.setErrorIfNoOtherErrors(ErrorMessage) an error message to the Result.
        • Recoverable user errors: Add a FeedbackHit explaining the condition and how to correct it.
        Specified by:
        search in class Searcher
        Parameters:
        query - the query
        Returns:
        the result of making this query