One of the component types that index managers coordinate are workers, which are responsible for the actual updates made to a Lucene index.
If you are using Lucene and Hibernate Search in a clustered environment, many of the configuration options are set at the worker level. We will explore those more fully in Chapter 7, Advanced Performance Strategies. However, three key configuration options are available in any environment.
By default, workers perform Lucene updates synchronously. That is, once an update begins, execution of the main thread is blocked until that update completes.
Workers may instead be configured to update asynchronously, a "fire and forget" mode that spawns a separate thread to perform the work. ...