---
title: Fix JMeter SNI Issue
url: https://blog.octoperf.com/fix-jmeter-sni-issue/
date: '2017-12-07'
authors:
- jloisel
categories:
- JMeter
tags:
- Design
- HTTP
- SSL
- JSR223
description: Got an handshake_alert or any other Https related issue with JMeter? It might be linked to Server Name Indication HTTPS extension.
---

# Fix JMeter SNI Issue

SNI is the acronym for [Server Name Indication](https://en.wikipedia.org/wiki/Server_Name_Indication):

> Server Name Indication (SNI) is an extension to the TLS computer networking protocol by which a client indicates which hostname it is attempting to connect to at the start of the handshaking process. 

SNI extension may not work with legacy web-servers who doesn't support it. Fortunately, SNI extension can be disabled in JMeter. JMeter is a Java program. Java has enabled SNI support in Java 7. The issue is typically displayed in JMeter as an *SSLHandshakeException*, with message like *handshake_failure* or *handshake alert:  unrecognized_name*.

JMeter uses [HTTPClient](https://hc.apache.org/index.html) to perform Http Requests. HttpClient uses the Java JDK SSL support mechanism. Therefore, disabling SNI support in the Java Virtual Machine will disable SNI in HttpClient.


## Disable SNI via JSR223

Put a [JSR223 Sampler](https://jmeter.apache.org/usermanual/component_reference.html#JSR223_Sampler) at the beginning of the Thread group, and set the following script:

    System.setProperty("jsse.enableSNIExtension", "false");

**It must be defined before any HTTP Sampler**, otherwise the setting won't be taken into account. See [JSR223 Samples](https://api.octoperf.com/doc/design/edit-virtual-user/action-types/jsr223-actions/jsr223-samples/#jvm-configuration-change) for more sample JSR223 scripts.

As shown in the screenshot above, the script is placed before any HTTP Sampler. It simply sets the system property.

[![JMeter JSR223 Disable SNI][1]][1]

## Disable SNI via JVM Args

Another way is to export *JVM_ARGS* before executing JMeter:

    export JVM_ARGS="-Djsse.enableSNIExtension=false"

Restart JMeter, and it should take into account the JVM setting. Of course, remember to do the same tweak on every load generator in case you run distributed load tests.

  [1]: ../img/blog/fix-jmeter-sni-issue/jsr223-disable-sni.png