[SOLR-2983] Unable to load custom MergePolicy

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 3.6, 4.0-ALPHA
• Assignee: Tommaso Teofili
• Reporter: Mathias Herberts
• Created: 21/Dec/11 10:39
• Updated: 10/May/13 10:40
• Resolved: 29/Mar/12 10:00

Description

As part of a recent upgrade to Solr 3.5.0 we encountered an error related to our use of LinkedIn's ZoieMergePolicy.

It seems the code that loads a custom MergePolicy was at some point moved into SolrIndexConfig.java from SolrIndexWriter.java, but as this code was copied verbatim it now contains a bug:

try {
policy = (MergePolicy) schema.getResourceLoader().newInstance(mpClassName, null, new Class[]

{IndexWriter.class}

, new Object[]

{this}

);
} catch (Exception e)

{ policy = (MergePolicy) schema.getResourceLoader().newInstance(mpClassName); }

'this' is no longer an IndexWriter but a SolrIndexConfig, therefore the call to newInstance will always throw an exception and the catch clause will be executed. If the custom MergePolicy does not have a default constructor (which is the case of ZoieMergePolicy), the second attempt to create the MergePolicy will also fail and Solr won't start.