# Set up Tomcat benchmark environment
## In this learning path
- [Introduction](https://learn.arm.com/learning-paths/servers-and-cloud-computing/java-perf-flamegraph/)
- [Set up Tomcat benchmark environment](https://learn.arm.com/learning-paths/servers-and-cloud-computing/java-perf-flamegraph/1_setup/)
- [Generate Java flame graphs using async-profiler](https://learn.arm.com/learning-paths/servers-and-cloud-computing/java-perf-flamegraph/2_async-profiler/)
- [Generate Java flame graphs using a Java agent](https://learn.arm.com/learning-paths/servers-and-cloud-computing/java-perf-flamegraph/3_agent/)
- [Next Steps](https://learn.arm.com/learning-paths/servers-and-cloud-computing/java-perf-flamegraph/_next-steps/)
## Overview
Flame graphs are a widely used entry point for analyzing Java application performance. Tools for generating flame graphs include `async-profiler`, Java agents, `jstack`, and Java Flight Recorder (JFR). This Learning Path focuses on two practical approaches: using `async-profiler` and a Java agent.
In this section, you’ll set up a benchmark environment using Apache Tomcat and `wrk2` to simulate HTTP load and evaluate performance on an Arm-based server.
## Set up the Tomcat benchmark server
[Apache Tomcat](https://tomcat.apache.org/) is an open-source Java Servlet container that runs Java web applications, handles HTTP requests, and serves dynamic content. It supports technologies such as Servlet, JSP, and WebSocket.
## Install the Java Development Kit (JDK)
Install OpenJDK 21 on your Arm-based Ubuntu server:
```bash
sudo apt update
sudo apt install -y openjdk-21-jdk
```
## Install Tomcat
First check that latest version of `tomcat 11` available with the following command.
```bash
TOMCAT_VERSION=$(wget -qO- https://downloads.apache.org/tomcat/tomcat-11/ \
| grep -oE 'v11\.0\.[0-9]+/' \
| sed 's#[v/]##g' \
| sort -V \
| tail -n1)
echo $TOMCAT_VERSION
```
Download and extract Tomcat:
```bash
wget -c "https://downloads.apache.org/tomcat/tomcat-11/v${TOMCAT_VERSION}/bin/apache-tomcat-${TOMCAT_VERSION}.tar.gz"
tar xzf "apache-tomcat-${TOMCAT_VERSION}.tar.gz"
```
If the command above fails, you can manually find the latest version on the [Tomcat 11 downloads page](https://downloads.apache.org/tomcat/tomcat-11/). Alternatively, you can build Tomcat [from source](https://github.com/apache/tomcat).
## Enable access to Tomcat examples
To access the built-in examples from your local network or external IP, use a text editor to modify the `context.xml` file by updating the `RemoteAddrValve` configuration to allow all IP addresses.
The file is at:
```bash
apache-tomcat-${TOMCAT_VERSION}/webapps/examples/META-INF/context.xml
```
```xml
__output__ from ...
__output__
__output__ to ...
__output__
```
## Start the Tomcat server
Start the server:
```bash
./apache-tomcat-${TOMCAT_VERSION}/bin/startup.sh
```
You should see output like:
```
Using CATALINA_BASE: /home/cesw/kiehej01/java-flamegraphs/apache-tomcat-11.0.22
Using CATALINA_HOME: /home/cesw/kiehej01/java-flamegraphs/apache-tomcat-11.0.22
Using CATALINA_TMPDIR: /home/cesw/kiehej01/java-flamegraphs/apache-tomcat-11.0.22/temp
Using JRE_HOME: /usr
Using CLASSPATH: /home/cesw/kiehej01/java-flamegraphs/apache-tomcat-11.0.22/bin/bootstrap.jar:/home/cesw/kiehej01/java-flamegraphs/apache-tomcat-11.0.22/bin/tomcat-juli.jar
Using CATALINA_OPTS:
Tomcat started.
```
## Confirm server access
In your browser, open: `http://${tomcat_ip}:8080`.
You should see the Tomcat welcome page and examples, as shown below:
*Apache Tomcat homepage*
*Apache Tomcat examples*
> Make sure port 8080 is open in the security group of the IP address for your Arm-based Linux machine.
## Set up the benchmarking client using wrk2
[Wrk2](https://github.com/giltene/wrk2) is a high-performance HTTP benchmarking tool specialized in generating constant throughput loads and measuring latency percentiles for web services. `wrk2` is an enhanced version of `wrk` that provides accurate latency statistics under controlled request rates, ideal for performance testing of HTTP servers.
> Currently `wrk2` is only supported on x86 machines. Run the benchmark client steps below on an `x86_64` server running Ubuntu.
## Install dependencies
Install the required packages:
```bash
sudo apt-get update
sudo apt-get install -y build-essential libssl-dev git zlib1g-dev
```
## Clone and build wrk2
Clone the repository and compile the tool:
```bash
sudo git clone https://github.com/giltene/wrk2.git
cd wrk2
sudo make
```
Move the binary to a directory in your system’s PATH:
```bash
sudo cp wrk /usr/local/bin
```
## Run the benchmark
Use the following command to benchmark the HelloWorld servlet running on Tomcat:
```bash
wrk -c32 -t16 -R50000 -d60 http://${tomcat_ip}:8080/examples/servlets/servlet/HelloWorldExample
```
You should see output similar to:
```
Running 1m test @ http://172.26.203.139:8080/examples/servlets/servlet/HelloWorldExample
16 threads and 32 connections
Thread calibration: mean lat.: 0.986ms, rate sampling interval: 10ms
Thread Stats Avg Stdev Max +/- Stdev
Latency 1.00ms 454.90us 5.09ms 63.98%
Req/Sec 3.31k 241.68 4.89k 63.83%
2999817 requests in 1.00m, 1.56GB read
Requests/sec: 49997.08
Transfer/sec: 26.57MB
```