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404 Not Found Error: Fix /actuator/prometheus Issue

9 min read 11-15- 2024
404 Not Found Error: Fix /actuator/prometheus Issue

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The "404 Not Found" error is a common issue that web users encounter while browsing the internet. This error typically occurs when a requested resource is not available on the server, which can be frustrating both for users and developers. One specific instance of this error that many developers face is related to the /actuator/prometheus endpoint in Spring Boot applications. In this blog post, we will explore what the "404 Not Found" error is, the common causes of this issue, and how to effectively troubleshoot and fix the /actuator/prometheus error in your Spring Boot application.

Understanding the 404 Not Found Error

What is a 404 Not Found Error? 🔍

A 404 Not Found error indicates that the server cannot find the requested resource. This can happen for various reasons, including:

  • The URL is incorrect or mistyped.
  • The resource has been deleted or moved without updating the URL.
  • The resource is not configured on the server.

Understanding this error is crucial for troubleshooting, as it can significantly affect the user experience and your application's performance.

Common Causes of the 404 Not Found Error

Misconfiguration in Spring Boot

In the context of Spring Boot applications, particularly when dealing with the Actuator and Prometheus, a 404 error can stem from several misconfigurations. Here are some common reasons:

  1. Actuator Not Enabled: Spring Boot Actuator must be explicitly enabled in your application for endpoints like /actuator/prometheus to work.

  2. Prometheus Dependency Missing: Ensure that the necessary dependency for Prometheus is included in your pom.xml or build.gradle.

  3. Invalid Endpoint Mapping: If the endpoint is mapped incorrectly in your application, the server won't be able to locate it, leading to a 404 error.

Additional Causes 🚧

Other potential causes may include:

  • Incorrect URL: Double-check to ensure that you are using the correct URL. The typical URL should look like http://yourdomain.com/actuator/prometheus.

  • Context Path Issues: If you have set a context path in your application, you need to include it when requesting the endpoint.

Steps to Fix the /actuator/prometheus 404 Not Found Error

Let’s delve into the steps you can take to fix the /actuator/prometheus issue in your Spring Boot application.

Step 1: Enable Spring Boot Actuator

To enable Actuator in your Spring Boot application, you need to add the required dependency. For Maven, add the following to your pom.xml:


    org.springframework.boot
    spring-boot-starter-actuator

If you are using Gradle, add the following to your build.gradle:

implementation 'org.springframework.boot:spring-boot-starter-actuator'

Step 2: Add Prometheus Dependency

Next, you need to include the Prometheus dependency for it to work seamlessly with Spring Boot Actuator. If you're using Maven, add this dependency:


    io.micrometer
    micrometer-registry-prometheus

For Gradle, use:

implementation 'io.micrometer:micrometer-registry-prometheus'

Step 3: Update application.properties or application.yml

You need to expose the Prometheus endpoint. Depending on your configuration, either your application.properties or application.yml file should be updated.

For application.properties, add:

management.endpoints.web.exposure.include=*

For application.yml, it would look like this:

management:
  endpoints:
    web:
      exposure:
        include: "*"

Step 4: Check the Application Configuration

Make sure your application's configuration is correct. It should look something like this in your main class:

@SpringBootApplication
public class MyApplication {
    public static void main(String[] args) {
        SpringApplication.run(MyApplication.class, args);
    }
}

Step 5: Validate the URL

Ensure that you are accessing the correct URL, including any necessary context paths. A correct URL for accessing the Prometheus metrics typically looks like:

http://localhost:8080/actuator/prometheus

If you have defined a different server port or context path, adjust the URL accordingly.

Step 6: Restart Your Application 🔄

After making these changes, don’t forget to restart your application. Often, changes will only take effect after a complete restart.

Step 7: Check for Logs and Errors

After restarting, check your application logs for any errors that might indicate further issues with the endpoint setup. Ensure there are no warnings or critical errors related to Actuator.

Step 8: Testing the Endpoint 🧪

Once you have completed the steps above, test your Prometheus endpoint by accessing it in your web browser or using a tool like curl:

curl http://localhost:8080/actuator/prometheus

If everything is configured correctly, you should see metrics data instead of a 404 error.

Troubleshooting Tips 🛠️

If the issue persists after following the above steps, consider the following troubleshooting tips:

  • Check Firewall Settings: Ensure that no firewall settings are blocking access to the application or specific endpoints.

  • Review Security Configuration: If you have Spring Security configured, make sure that your security settings allow access to the /actuator/prometheus endpoint.

  • Upgrade Dependencies: Ensure that you are using the latest stable versions of Spring Boot and related libraries, as bugs may have been fixed in newer releases.

  • Consult the Documentation: Always refer to the official Spring Boot documentation for Actuator and Prometheus for the most up-to-date configuration options.

Summary

A "404 Not Found" error when accessing /actuator/prometheus in your Spring Boot application can be frustrating, but it is often straightforward to fix. By ensuring that your Actuator and Prometheus dependencies are correctly set up, enabling the necessary configurations, and checking for possible misconfigurations, you can effectively resolve this issue.

By following the outlined steps and tips, you should be able to troubleshoot and fix the /actuator/prometheus error in your application, leading to a smoother user experience and more accurate monitoring with Prometheus.

Remember, maintaining a well-configured Spring Boot application is key to preventing such errors from arising in the first place. Regularly review your application configurations, keep dependencies updated, and test your endpoints thoroughly.

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