[SOLR-13195] NPE caused by distributed queries when no shards are configured

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 9.0
• Component/s: FacetComponent
• Labels: diffblue newdev

Environment

Steps to reproduce

• Use a Linux machine.
• Build commit ea2c8ba of Solr as described in the section below.
• Build the films collection as described below.
• Start the server using the command ./bin/solr start -f -p 8983 -s /tmp/home
• Request the URL given in the bug description.

Compiling the server

git clone https://github.com/apache/lucene-solr
cd lucene-solr
git checkout ea2c8ba
ant compile
cd solr
ant server

Building the collection

We followed Exercise 2 from the Solr Tutorial. The attached file (home.zip) gives the contents of folder /tmp/home that you will obtain by following the steps below:

mkdir -p /tmp/home
echo '<?xml version="1.0" encoding="UTF-8" ?><solr></solr>' > /tmp/home/solr.xml

In one terminal start a Solr instance in foreground:

./bin/solr start -f -p 8983 -s /tmp/home

In another terminal, create a collection of movies, with no shards and no replication, and initialize it:

bin/solr create -c films
curl -X POST -H 'Content-type:application/json' --data-binary '{"add-field": {"name":"name", "type":"text_general", "multiValued":false, "stored":true}}' http://localhost:8983/solr/films/schema
curl -X POST -H 'Content-type:application/json' --data-binary '{"add-copy-field" : {"source":"*","dest":"_text_"}}' http://localhost:8983/solr/films/schema
./bin/post -c films example/films/films.json

• Assignee: Unassigned
• Reporter: Johannes Kloos
• Created: 31/Jan/19 11:17
• Updated: 01/Feb/21 21:28

Description

Requesting the following URL causes Solr to return an HTTP 500 error response:

http://localhost:8983/solr/films/select?distrib=true&facet=on&facet.field=genre

The error response seems to be caused by the following uncaught exception:

null:java.lang.NullPointerException
at org.apache.solr.handler.component.FacetComponent$DistribFieldFacet.<init>(FacetComponent.java:1432)
at org.apache.solr.handler.component.FacetComponent$FacetInfo.parse(FacetComponent.java:1266)
at org.apache.solr.handler.component.FacetComponent.modifyRequest(FacetComponent.java:528)
at org.apache.solr.handler.component.ResponseBuilder.addRequest(ResponseBuilder.java:162)
at org.apache.solr.handler.component.QueryComponent.createMainQuery(QueryComponent.java:755)
at org.apache.solr.handler.component.QueryComponent.regularDistributedProcess(QueryComponent.java:546)
at org.apache.solr.handler.component.QueryComponent.distributedProcess(QueryComponent.java:499)
at org.apache.solr.handler.component.SearchHandler.handleRequestBody(SearchHandler.java:348)

Since the query contains “distrib=true”, it is handled by calling the distributedProcess methods of the search pipeline. At no point in the call chain that leads to the above exception is there any check if the ResponseBuilder rb used to handle the request actually has its shared property configured. Nevertheless, the DistribFieldFact constructor tries to access rb.shards.length, but rb.shared is null in this example.

We found this bug using Diffblue Microservices Testing. Find more information on this fuzz testing campaign.

Issue Links

• links to: GitHub Pull Request #1589