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services.xml - 'search'

This is the reference for the search part of the container config. Related: Chained components and the federation tutorial. The root element of the search configuration, declared as a subelement to container:

search
    binding
    searcher [id, class, bundle, provides, before, after]
    federation [id]
        source [idref]
            federationoptions [timeout, requestTimeout, optional]
        source-set [inherits]
        target-selector
    chain [id, inherits, excludes]
        searcher [id, class, bundle, provides, before, after]
        federation [id]
            source [idref]
                federationoptions [timeout, requestTimeout, optional]
            source-set [inherits]
            target-selector
    provider [id, type, cluster, excludes]
        federationoptions [timeout, requestTimeout, optional]
        source [id]
            searcher [id, class, bundle, provides, before, after]
    renderer [id, class, bundle]
    threadpool
        threads [ boost ]
        queue

config applies to all searchers in the JDisc cluster's search chains, unless overridden by individual search chains or searchers.

binding

The URI to map the SearchHandler to. The default binding is http://*/search/*. Multiple elements are allowed. Example:

<binding>http://*/search/*</binding>

searcher

Searcher elements are contained in chain elements or in the search root.

A searcher element is either a definition (using id) or a reference (using idref).

A searcher definition causes the creation of exactly one searcher instance. This instance is set up according to the content of the searcher element. A searcher definition contained in a search chain element defines an inner searcher. Otherwise, it defines an outer searcher.

Searcher definition:

Attribute	Required	Value	Description
id	required	string	The component id of the searcher instance. For inner searchers, the id must be unique inside the search chain. For outer searchers, the id must be unique. An inner searcher is not permitted to have the same id as an outer searcher.
class	optional		A component specification containing the name of the class to instantiate to create the searcher instance. If missing, copied from id
bundle	optional		A component specification containing the bundle symbolic name and version used to select the bundle: The name in <artifactId> in pom.xml. The class is loaded from this bundle. If no bundle is specified, it defaults to the bundle containing the searchers bundled with Vespa.
provides	optional		A space-separated list of names that represents what this searcher produces. For more information on provides, before and after, see chained components
before	optional		A space-separated list of phase or provided names. Phases or searchers providing these names will be placed later in the search chain than this searcher
after	optional		A space-separated list of phase or provided names. Phases or searchers providing these names will be placed earlier in the search chain than this searcher

Example:

<searcher id="componentId"
          class="className:versionSpecification"
          bundle="the name in <artifactId> in pom.xml" />

Searcher reference:

Attribute	Required	Value	Default	Description
idref	required	string		Reference to a searcher definition

Example:

<searcher idref="componentId" />

federation

A federation is a searcher - see above. This element implements federation - it defines a searcher instance that sends each query to a set of search chains in parallel and combines the results. Read the federation guide to learn more and find examples for use of federation and its children source, source-set and target-selector, as well as provider.

<federation id="componentId">
    <source idref="componentSpecification" />
    <target-selector />
</federation>

target-selector

Specifies a component that should be used to select search chains to federate to. This component must inherit from com.yahoo.search.federation.selection.TargetSelector. See component for attributes and subelements.

source-set

Used to duplicate the sources of e.g. the built-in federation searcher:

<federation id="combinator">
    <source-set inherits="default" />
    …
</federation>

source

Reference to a source that should be used by the enclosing federation searcher. Child element federationoptions is optional.

<source idref="componentSpecification">
    <federationoptions/>
</source>

federationoptions

Contained in source or provider. Specifies how a federation searcher should federate to a given search chain. If a federation options A overrides another federation options B, the result is a new federation options containing:

all the options in B not present in A
all the options in A

When federating to a source or provider, the federation searcher per default uses the federation options from the search chain. If a source reference contains federation options, it overrides the options of the search chain when used from the enclosing federation searcher.

Attribute	Required	Value	Default	Description
timeout	optional	number		The minimum number of seconds or milliseconds (if ms is present) the federation searcher waits for the federated search chain executing the query
requestTimeout	optional	number		The minimum number of seconds or milliseconds (if ms is present) the search chain executing the query should continue execution. In some cases it is useful to set this higher than the timeout, such that a chain can keep waiting for requested data longer than the query is waiting for the chain. This allows queries to populate caches within the search chain even though populating the caches requires waiting longer than the query timeout
optional	optional	true/false	false	Determines if the federation searcher should wait for this search chain at all. Normally, it only waits for mandatory (i.e. not optional) search chains, and when they are done, cancels the remaining search chains that are not finished. If all the search chains federated to are optional, all of them will be treated as mandatory. All search chains are per default mandatory

Example:

<federationoptions timeout="2.0" requestTimeout="2500ms" optional="true" />

renderer

The definition of a search result renderer.

Attribute	Required	Value	Description
id	required	string	The component ID
class	optional	string	The class of the component, defaults to id
bundle	optional	string	The bundle to load the component from: The name in <artifactId> in your pom.xml. If no bundle is given, the bundle containing renderers provided by Vespa is used.

Example:

<renderer id="componentId"
          class="className:versionSpecification"
          bundle="the name in <artifactId> in pom.xml" />

chain

Specifies how a search chain should be instantiated, and how the contained searchers should be ordered. Refer to the chain reference for attributes and child elements. Chains can inherit searchers from other chains and use phases for ordering. Note that provider and source elements are also chains. Specify a search chain in a query using searchChain.

Example which inherits from the built in vespa chain so that the searcher can dispatch queries to the content clusters:

<chain id="common" inherits="vespa">
    <searcher class="com.yahoo.vespatest.ExtraHitSearcher" id="CommonSearcher" bundle="the name in <artifactId> in your pom.xml" >
        <config name="vespatest.extra-hit">
            <exampleString>A searcher for ...</exampleString>
        </config>
    </searcher>
</chain>

Optional sub-elements:

searcher or federation (one or more), either a reference or definition. If the name given for a searcher matches an outer searcher, it is a searcher reference. Otherwise, it is a searcher definition. If it is a searcher definition, it is also an implicit searcher reference saying: use exactly this searcher. All these searcher elements must have different name.
phase (one or more).
config (one or more - will apply to all inner searchers in this search chain, unless overridden by individual inner searchers).

You can put search config in separate files in a directory under the application package using include. Each file must contain one <search> element like above. Vespa behaves as if each chain configured within was "inline" in services.xml. This is handy when multiple developers need to deploy individual search chains, say in different packages.

Note: If using multiple container clusters, the modular search chains will be available in all the clusters.

Each searcher reference must match the type of the searcher definition. So for example the searcher reference federation idref="myId" must match an outer searcher defined as federation id="myId", not searcher id="myId".

provider

A provider is a search chain responsible for talking to an external service. Everything covered in chain is also valid for providers.

Attribute	Required	Value	Description
id	required	string	ID
excludes	optional
type	optional	local	Determines which searchers are implicitly added to this search chain to talk to the external service.

local provider

Local providers are providers with the type set to local, accessing a local Vespa cluster (i.e. a content cluster in the same application).

Attribute	Required	Value	Default	Description
cluster	required	string		The name of the local cluster.

<provider id="music" cluster="music" type="local" excludes="com.yahoo.prelude.querytransform.StemmingSearcher" />

source

Defines a source search chain and an associated source.

<provider id="providerA">
    <source id="commonSource">
        <searcher id="com.yahoo.example.AddHitSearcher" bundle="the name in <artifactId> in your pom.xml" >
            <config name="vespatest.hit-title">
                <hitTitle>providerA</hitTitle>
            </config>
        </searcher>
    </source>
</provider>

The component id specified is the id of the associated source. The associated source consists of all the source search chains with the same source name.

Only a single source search chain can specify the source name using the "id" attribute. This search chain is called the leader. The other source search chains must specify the source name using the "idref" attribute. The latter search chains are called participants.

A source can be used for federation. When federating to a source, the leader search chain is normally used. To use one of the participant search chains, the following query parameter must be set: source.sourceId.provider.providerId.

The id of the source search chain is sourceId@providerId. This search chain automatically inherits from the enclosing provider. It also automatically inherits the federation options of the enclosing provider. If the source contains federation options, they override the inherited ones. In all other respects, this search chain behaves like any other search chain.

threadpool

Specifies configuration for the thread pool for the jdisc search handler. All parameters are relative to the number of CPU cores - if a node has 8 vCPU with threads=4, the thread pool will have 32 threads. Same for queue size - if queue=10, the queue will have capacity for 80 entries. If the boost attribute is specified, additional threads will be created on demand once the request queue is full. These threads are then destructed after idling for a fixed amount of time. Requests are rejected once the maximum number of allowed threads is reached, all threads are busy and the request queue is full. See Container Tuning for more details.

threads

The number of permanent threads relative to CPU cores. Default value is 2.

Attribute	Required	Value	Default	Description
boost	optional	number		The number of additional threads relative to CPU cores. Default value is `2`.

queue

The size of the request queue relative to CPU cores. Specify 0 to disable queuing. Default value is 40.