---
title: Setting number of threads in the Elasticsearch Java REST 5 client
description: The Apache Http Async Client starts by default one dispatcher thread, and a number of worker threads used by the connection manager, as many as the number...
url: https://docs-v3-preview.elastic.dev/elastic/elasticsearch-java/pull/1224/reference/transport/rest5-client/config/number_of_threads
products:
  - Elasticsearch Client
---

# Setting number of threads in the Elasticsearch Java REST 5 client
The Apache Http Async Client starts by default one dispatcher thread, and a number of worker threads used by the connection manager, as many as the number of locally detected processors (depending on what `Runtime.getRuntime().availableProcessors()` returns). The number of threads can be modified as follows:
```java
Rest5ClientBuilder builder = Rest5Client
    .builder(new HttpHost("localhost", 9200))
    .setHttpClientConfigCallback(c -> c
        .setIOReactorConfig(IOReactorConfig.custom()
            .setIoThreadCount(1).build()
        )
    );
```