com.yahoo.search.searchers

Class CacheControlSearcher

java.lang.Object

com.yahoo.component.AbstractComponent

com.yahoo.component.chain.ChainedComponent

com.yahoo.processing.Processor

com.yahoo.search.Searcher

com.yahoo.search.searchers.CacheControlSearcher

All Implemented Interfaces:

com.yahoo.component.Component, 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

Field Summary

Fields

Modifier and Type	Field and Description
static String	CACHE_CONTROL_HEADER
private static com.yahoo.processing.request.CompoundName	cachecontrolMaxage
private static com.yahoo.processing.request.CompoundName	cachecontrolNocache
private static com.yahoo.processing.request.CompoundName	cachecontrolStaleage

Fields inherited from class com.yahoo.component.AbstractComponent

isDeconstructable

Constructor Summary

Constructors

Constructor and Description
CacheControlSearcher()

Method Summary

Modifier and Type	Method and Description
Result	search(Query query, Execution execution) Override this to implement your searcher.

Methods inherited from class com.yahoo.search.Searcher

ensureFilled, fill, getLogger, process, toString

Methods inherited from class com.yahoo.component.chain.ChainedComponent

getAnnotatedDependencies, getDefaultAnnotatedDependencies, getDependencies, initDependencies

Methods inherited from class com.yahoo.component.AbstractComponent

clone, compareTo, deconstruct, getClassName, getId, getIdString, hasInitializedId, initId, isDeconstructable, setIsDeconstructable

Methods inherited from class java.lang.Object

equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

cachecontrolNocache

private static final com.yahoo.processing.request.CompoundName cachecontrolNocache

cachecontrolMaxage

private static final com.yahoo.processing.request.CompoundName cachecontrolMaxage

cachecontrolStaleage

private static final com.yahoo.processing.request.CompoundName cachecontrolStaleage

CACHE_CONTROL_HEADER

public static final String CACHE_CONTROL_HEADER

See Also:

Constant Field Values

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