Writing a language plugin to run a script

cmelean · July 18, 2018, 1:20pm

I am migrating a few scripts from Groovy to Painless, and running into the following issue at runtime:
"Scripts may be no longer than 16384 characters.. . Consider using a plugin if a script longer than this length is a requirement."

So I've been trying to figure out how to write a plugin that would run the scripts I have and not having any luck. The only relevant example I've seen is this:

github.com

elastic/elasticsearch/blob/v6.3.1/plugins/examples/script-expert-scoring/src/main/java/org/elasticsearch/example/expertscript/ExpertScriptPlugin.java

/*
 * Licensed to Elasticsearch under one or more contributor
 * license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright
 * ownership. Elasticsearch licenses this file to you under
 * the Apache License, Version 2.0 (the "License"); you may
 * not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.elasticsearch.example.expertscript;

This file has been truncated. show original

But It doesn't apply entirely. From my failed attempts it sounds like a need to figure out how instantiate a ExecutableScript factory and script, but not sure. It has been hard to find documentation or examples on the web.

The latest error I am getting is this (but could be because the plugin code is not correct):

Caused by: NotSerializableExceptionWrapper[class_cast_exception: Cannot cast com.mobius.ESPlugin$MyExpertScriptEngine$$Lambda$2912/1589848714 to org.elasticsearch.script.SearchScript$Factory]

I am wondering if someone can point me to other examples, specifically on just implementing scripts in a plugin. The scripts I am migrating are used in aggregations, so I have one initScript, one mapScript and one reduceScript.

Also if there is any other workaround for the max number of Painless characters issue, I'd appreciate any thoughts as well. I've already tried shrinking the code as much as I can. It's legacy code.

Thanks in advance.

cmelean · July 19, 2018, 1:14pm

Never mind. I figured out how to write the plugin. Thanks

system · August 16, 2018, 1:25pm

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Writing a language plugin to run a script

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