Custom JavaScript Stages for Query Pipelines

Table of Contents

The JavaScript Engine Used by Fusion
JavaScript Query Stage Global Variables
- Syntax Variants
- Global variable logger
See also

The JavaScript Query stage allows you to write custom processing logic using JavaScript to manipulate search requests and responses. The first time that the pipeline is run, Fusion compiles the JavaScript program into Java bytecode using the JDK’s JavaScript engine.

The JavaScript Query stage allows you to run JavaScript functions over search requests and responses by manipulating variables called "request" and "response" which are Request objects and Response objects, respectively.

Users who can create or modify code obtain access to the broader Fusion environment. This access can be used to create intentional or unintentional damage to Fusion.

The JavaScript Engine Used by Fusion

The default JavaScript engine used by Fusion is the Nashorn engine from Oracle. See The Nashorn Java API for details.

In Fusion 5.9.6 and up, you also have the option to select OpenJDK Nashorn. While Nashorn is the default option, it is in the process of being deprecated and will eventually be removed, so it is recommended to use OpenJDK Nashorn when possible. You can select the JavaScript engine in the pipeline views or in the workbenches. Your JavaScript pipeline stages are interpreted by the selected engine.

JavaScript engine selector

The GraalVM engine from Oracle is also available. Select GraalVM from the JavaScript engine dropdown to use it. See GraalVM for details. GraalVM works in Nashorn compatibility mode and should not be used in production. Full backwards compatibility is not available.

JavaScript Query Stage Global Variables

JavaScript is a lightweight scripting language. The JavaScript in a JavaScript stage is standard ECMAScript. What a JavaScript program can do depends on the container in which it runs. For a JavaScript Query stage, the container is a Fusion query pipeline. The following global pipeline variables are available:

Name Type Description

request

Request for a Regular Query

The request variable contains Solr query information and is referred to as a regular request. A regular query request does not include Search DSL (domain specific language) parameters.

request

DSL Request

The request variable is also used when the query contains parameters for a Search DSL (domain specific language) request.

See Domain Specific Language for more information.

response

Response for a Regular Query

The response variable contains Solr response information, and is used to return information from a regular request. Because a regular request does not include Search DSL (domain specific language) parameters, the response will not return Search DSL results.

response

DSL Response

The response variable is also used to return information from a Search DSL (domain specific language) request.

See Domain Specific Language for more information.

ctx

Context

A map that stores miscellaneous data created by each stage of the pipeline.

Use the ctx variable instead of the deprecated _context global variable.

The ctx variable is used to:

Pass data from one stage to another
Store data that needs to be passed from one custom stage to a later custom stage

The data can differ between stages:

If the previous stage changes the data
Based on the configuration of each stage

If the data is modified in one stage, it may cause a later stage to function irregularly.

collection

String

The name of the Fusion collection being indexed or queried.

solrServer

BufferingsolrServer

The Solr server instance that manages the pipeline’s default Fusion collection. All indexing and query requests are done by calls to methods on this object. See solrClient for details.

solrServerFactory

solrClusterComponent

The SolrCluster server used for lookups by collection name which returns a Solr server instance for that collection, e.g.
var productsSolr = solrServerFactory.getSolrServer("products");.

QueryRequestAndResponse

QueryRequestAndResponse

Used to create query pipeline requests and responses.

JSONResponse

JSONResponse

Returns list of info as a string.

See Custom JavaScript Query Stage Examples for more information.

Syntax Variants

JavaScript stages can be written using function syntax. With function syntax, global variables are passed as function parameters.

Support for legacy syntax was removed in Fusion 5.8.

Function Syntax

function(request,response) {
   request.addParam("foo", "bar");
}

Function syntax is used for the examples in this document.

Global variable `logger`

The logs are output to the query service logs for custom query stages. Access the Log Viewer and filter on this service to view the information.