DEV Community: Alex John Chamba

Generate database documentation with SchemaSpy & Docker (Windows, Linux, macOS)

Alex John Chamba — Thu, 26 Mar 2026 02:32:07 +0000

Introduction

SchemaSpy is a tool that allows you to generate interactive HTML documentation from databases. In this guide, I will use Oracle as an example, but you can also use SchemaSpy with PostgreSQL, MySQL, SQL Server, etc. Thanks to Docker, you can easily run it on Windows, Linux, or macOS. Let's get started! 🚀

Prerequisites

Docker installed on your system:

Docker Desktop
JDBC driver. Tis image includes drivers for:
MySQL
MariaDB
PostgreSQL
jTDS

If you use any of these, you do not need to download any drivers.

Since this guide uses Oracle Database as an example, you will need to download the Oracle JDBC driver ojdbc11.jar from the Oracle website.

Getting Started

Step 1: Create the working directory

Open your terminal and run:

mkdir schemaspy-doc && cd schemaspy-doc
mkdir drivers output

Step 2: Add the JDBC driver

Move the downloaded driver (in this case ojdbc11.jar) into the drivers/ folder.

Step 3: Create `schemaspy.properties`

Create a schemaspy.properties file with the following content:

schemaspy.t=orathin-service
schemaspy.driver=oracle.jdbc.OracleDriver

schemaspy.host=server_or_ip
schemaspy.port=1521
schemaspy.db=db_name
schemaspy.u=database_user
schemaspy.p=database_password
schemaspy.schema=schema_name

schemaspy.norows=true
schemaspy.noviews=true
# Required in Oracle
schemaspy.cat=%

Not sure what value to use for the schemaspy.t parameter? 👀 Run:

docker run --rm schemaspy/schemaspy -dbHelp

You will get a list of supported database types and the parameters each one requires.

Step 4: Run SchemaSpy with Docker

On Linux/macOS:

docker run --rm \
  -v "$(pwd)/schemaspy.properties:/schemaspy.properties" \
  -v "$(pwd)/output:/output" \
  -v "$(pwd)/drivers:/drivers" \
  schemaspy/schemaspy

On Windows:

docker run --rm `
  -v "${PWD}/schemaspy.properties:/schemaspy.properties" `
  -v "${PWD}/output:/output" `
  -v "${PWD}/drivers:/drivers" `
  schemaspy/schemaspy

If you use localhost as the database host within the Docker container, it will not work because localhost points to the container itself, not to your host machine. ⚠️

Solution: Use host.docker.internal as the host to connect from the container to your local machine. For example:
schemaspy.host=host.docker.internal

Step 5: View the generated documentation

Once the command finishes, open the output/index.html file in your favorite web browser. You’ll find:

Entity relationship diagrams
Table structures
Columns, indexes, relationships, etc
A beautiful (and clickable!) and interactive HTML interface

Example Output 📸

REST API Load performance testing using JMeter

Alex John Chamba — Thu, 30 Jan 2025 03:14:58 +0000

Introduction

JMeter is the perfect tool to test the performance of your REST API. In this guide, I'll show you how to set it up and run a load test in minutes in a straightforward way. Let's get started! 🚀

Prerequisites

JMeter installed.
A REST API to test (we will use https://restcountries.com/v3.1/translation/germany)

Configuring the Test Plan

1. Add a Thread Group

Open JMeter and right click on Test Plan -> Add -> Threads -> Thread Group

2. Add an HTTP Request

Right click on Thread Group -> Add -> Sampler -> HTTP Request

3. Fill in the necessary values

Method: GET
URL: https://restcountries.com/v3.1/translation/germany

4. Add a Listener to see the Request response

Right click on Thread Group -> Add -> Listener -> View Results Tree

5. Save and Run

Save the changes (this creates a .jmx file), then press the Start button to run a test.

View results:

6. Update Thread properties
Adjust the thread properties according to the load level you want to simulate.

Running the Load Test

Optimizing JMeter 🛠️ (Optional)

To avoid JMeter consuming too many resources:

Use as few Listeners as possible.
Don't use "View Results Tree" or "View Results in Table" listeners during the load test, use them only during Test Plan creation and debugging. Disable the listener by right-clicking View Results Tree -> Disable.
Make sure you have Java 21 installed.
Increase Java Heap size to 2 GB or more, this depends on your test plan and number of threads you want to run. To do this, create a setenv.sh file in the JMeter bin directory:

# This is the example file jmeter/libexec/bin/setenv.sh

# Use a bigger heap, but a smaller metaspace, than the default
export HEAP="-Xms2G -Xmx2G -XX:MaxMetaspaceSize=192m"

Running JMeter in CLI Mode

Once everything is ready, you will use CLI mode (Previously called Non-GUI mode) to run it for the Load Test.

⚠️ Don't use GUI mode for Load Testing ! Use it only for Test Plan creation and Test Plan debugging.

Run JMeter in CLI mode:

jmeter -n -t ~/Documents/View-Results.jmx

Run JMeter in CLI mode and generate a report:

jmeter -n -t ~/Documents/View-Results.jmx -l ~/Documents/logs/test-results.jtl -e -o ~/Documents/results/

Parameters used:

-n, run JMeter in CLI mode
-t <argument>, name of .jmx file that contains the Test Plan to run
-l <argument>, name of .jtl file to log sample results
-e generate report dashboard
-o <argument> output folder where to generate the report dashboard (Folder must not exist or be empty)

Analyzing the Load Test

Once your Load Test is finished, you can use the HTML report to analyze your load test. To do this, you must open the results/index.html file.

Done! You now have a working load test. 🚀

DEV Community: Alex John Chamba

Generate database documentation with SchemaSpy & Docker (Windows, Linux, macOS)

Introduction

Prerequisites

Getting Started

Step 1: Create the working directory

Step 2: Add the JDBC driver

Step 3: Create schemaspy.properties

Step 4: Run SchemaSpy with Docker

Step 5: View the generated documentation

REST API Load performance testing using JMeter

Introduction

Prerequisites

Configuring the Test Plan

Running the Load Test

Optimizing JMeter 🛠️ (Optional)

Running JMeter in CLI Mode

Analyzing the Load Test

Step 3: Create `schemaspy.properties`