[SOLR-972] EventListener-s creation changed from a per request ( full / delta-imports) scenario to once through the lifetime of the DIH plugin.

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Won't Fix
• Fix Version/s: 1.4
• Component/s: contrib - DataImportHandler

Environment

Java 6, Tomcat 6

• Assignee: Unassigned
• Reporter: Karthik K
• Created: 19/Jan/09 22:17
• Updated: 10/Nov/09 15:51
• Resolved: 05/Feb/09 08:53

Description

The EventListener plugin for notification of start / end import events (SOLR-938) creates an instance of EventListener before every notification. This has 2 drawbacks.

• No state is stored between successive invocations of events as it is a new object
• When writing plugins for delta imports - it is very inefficient to do a class loader lookup by reflection / instantiate an instance and call a method on the same.

Attached patch has one EventListener through the lifetime of the DIH plugin .

Also EventListener is changed to an interface rather than an abstract class for better decoupling (especially painful when the start/end eventlistener has an independent hierarchy by itself ).

By default, a no-op listener is registered to avoid boiler plate code to check if there is a start / end listener specified. Efficient JRE impls should be able to optimize the no-op for minimum overhead compared to checking the reference for null and branching out.

Specifying an onImportStart / onImportEnd overrides the default handler though.

Issue Links

• is related to: SOLR-938 DataImportHandler: Add close hooks to the completion of a full-import process
• is related to: SOLR-935 DataImportHandler: Add logging to record failure to acquire lock by DataImporter for a given request
• relates to: SOLR-988 Add a new scope for DIH session to store objects across imports