Custom JavaScript stages for query pipelines
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, Managed 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 Managed Fusion environment. This access can be used to create intentional or unintentional damage to Managed Fusion. |
The JavaScript engine used by Managed Fusion
The JavaScript engine used by Managed Fusion is the Nashorn engine from Oracle. See The Nashorn Java API for details.
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 Managed Fusion query pipeline. The following global pipeline variables are available:
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A map that stores miscellaneous data created by each stage of the pipeline.
The
The data can differ between stages:
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String |
The name of the Managed Fusion collection being indexed or queried. |
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The Solr server instance that manages the pipeline’s default Managed Fusion collection. All indexing and query requests are done by calls to methods on this object. See solrClient for details. |
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The SolrCluster server used for lookups by collection name which returns a Solr server instance for that collection, e.g. |
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Used to create query pipeline requests and responses. |
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Returns list of info as a string. |
See Custom JavaScript Query Stage examples for more information. |
Syntax variants
JavaScript stages can be written using legacy syntax or function syntax. The key difference between these syntax variants is how the "global variables" are used and interpreted. While using legacy syntax, these variables are used as global variables. With function syntax, however, these variables are passed as function parameters.
Legacy syntax
request.addParam("foo", "bar");
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.
See also
Lucidworks offers free training to help you get started with Fusion. Check out the JavaScript in Fusion course, which focuses on how to leverage JavaScript in Fusion to build powerful and responsive scripts at index and query time: Visit the LucidAcademy to see the full training catalog. |