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SKP’s Java/Java EE Gotchas: Clustered Nodes Issue Using Apache Lucene 5.4.y

So, We just spent about 28+ days — using Stack Overflow and Hibernate Search Forums as also various other resources to 'FIX' the strangest of issues using Hibernate Search and Apache Lucene. The right help or pointer came from the 'Hibernate Search Committers/Creators' (Official Forums). Thanks a lot to 'sanne.grinovero'.

Issue Description: In a (non-replicated) clustered environment, if the Indexing by Lucene or Hibernate Search is done from the Same Database (Instance) using the Same Data the Results obtained are Different on Different Nodes. In other words, the Same Data from the Same Database Instance Indexed using the Same Code Yields a Different Result Set for the Same Search Term (Index Contents are Different on Different Machines).


Issue Resolution / Root Cause: The point to note is that, if you open a 'Hibernate Session' that you use for your 'Apache Lucene or Hibernate Search Indexing' and if a 'Runtime/Exception' occurs before you 'Close' the session, the results that are obtained across different machines, when queried using the same search term. Though this occurred after the 'console logs' reported that the Index is '100% Successfully Completed' — It has led to an inconsistent index across machine. My analysis is that 'session.close()' below may be leading to some 'flushing or committing to the indexing', which leads to the inconsistency when a runtime exception occurs — even after indexing is reported complete by the Hibernate/Hibernate Search on the 'Console Logs'.

Suggestion: Make sure that there are no Runtime Exceptions (or Errors) before Closing the Session. Even if you find that the Indexing is 100% Complete and there is an Exception right at the End — Please do not Ignore/Keep/Park it (Considering it a Minor or Unrelated Error) for a fix at the 'End of Dev Cycle' as it may Impact Results. This is true for any seemingly unrelated exception that may occur before calling 'session.close()'.

I am pasting the statement here from Hibernate Search Forums (Committer), which may be useful for all of you and helped us to finally resolve this error:  If a batch of documents failed, you might have a block of documents missing in one of the indexes (and this could happen several times). By default errors are logged, you might want to hook up an ErrorHandler to raise a more serious notification to your admins — if logs are ignored.



The culprit line of code, pointed out in red. [CULPRIT LINE OF CODE - WHERE RUNTIME EXCEPTION OCCURS - POINTED OUT USING ARROW]

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Best Performance Practices for Hibernate 5 and Spring Boot 2 (Part 1)

Item 1: Attribute Lazy Loading Via Bytecode Enhancement

By default, the attributes of an entity are loaded eager (all at once). Are you sure that you want that?

Description: If not, then is important to know that attributes can be loaded lazily, as well via Hibernate bytecode instrumentation (another approach is via subentities). This is useful for column types that store large amounts of data: CLOB, BLOB, VARBINARY, etc.

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Hibernate Bytecode Enhancement: Association Management

In the previous article, Hibernate Bytecode Enhancement. Dirty Tracking, I explained how to optimize Hibernate’s Dirty Tracking mechanism.

The bytecode enhancement, however, can be achieved via one more property: association management. When this feature is enabled, Hibernate will take care of automatically updating the “other side” of a bidirectional relation with a reverse mapping defined when one side changes. Similar to Dirty Tracking, this will as well result in additional changes made to the bytecode of the entities.

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Hibernate Envers: Simple Implementations (Part 1)

Introduction

Auditing is an important part of software applications. Almost every business domain requires an audit log to manage the changes of acquired data. More than that, auditing is also required to keep applications safe from fraudulent and unethical access. Many applications also check the changelog of data for their internal processes. Many Java-based software implement triggers on the database layer for auditing, but Hibernate gives a more convenient way to implement auditing.

Hibernate Envers: Features

Hibernate Envers is a framework for auditing. Though Hibernate is an ORM technology, auditing tasks based on Hibernate entities means changes on the entity is audited and saved on the database. Auditing of all mappings is defined by the JPA specification. Revision of each entity log is saved by Hibernate Envers. Hibernate Envers gives the way to read historical data log. 

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Optimizing Relationships Between Entities in Hibernate

In this post, following the example project that you have here, I am going to explain how to optimize queries to a database using JPA.

You will see different types of queries explaining how to make connections between lazy and eager tables. The tables will be joined by a single field, by several and even by one, but adding a static condition.