`included_applications: [:os_mon]` Causes Critical Mix Error

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Introduction

When working with Elixir and Erlang, mix releases are a crucial part of the development process. However, sometimes, unexpected errors can occur, causing frustration and delays. In this article, we will explore a specific issue that arises when running mix release in an application, specifically the error ** (Mix) :os_mon is listed both as a regular application and as an included application. We will delve into the root cause of this problem, identify the culprit, and provide a step-by-step solution to resolve the issue.

Describe the Bug

When running mix release in our application, we encountered the following error:

** (Mix) :os_mon is listed both as a regular application and as an included application

This error message indicates that there is a conflict between the regular applications and the included applications in the mix.exs file. To better understand the issue, let's take a closer look at the mix.exs file.

Environment

Before we dive into the solution, it's essential to note the environment in which this issue occurred:

  • Elixir & Erlang version (elixir -v): 1.18.3
  • Agent version (mix deps | grep new_relic_agent): 1.35.0

The Culprit: new_relic_agent

After searching through our dependencies, we discovered that the new_relic_agent was the culprit behind this issue. In the mix.exs file, there was the following line included:

included_applications: [:os_mon]

This line was causing the conflict between the regular applications and the included applications.

Understanding the Issue

To better understand the issue, let's break down the concept of regular applications and included applications.

  • Regular Applications: These are applications that are explicitly listed in the mix.exs file under the applications section. They are compiled and started by the mix release.
  • Included Applications: These are applications that are included in the mix release, but not explicitly listed in the mix.exs file. They are compiled and started by the mix release, but not as separate applications.

In our case, the os_mon application was listed both as a regular application and as an included application. This caused the conflict, resulting in the error message.

Solution

To resolve this issue, we need to remove the os_mon application from the included_applications list in the mix.exs file. We can do this by commenting out or removing the following line:

# included_applications: [:os_mon]

Alternatively, we can remove the os_mon application from the applications list in the mix.exs file, if it's not required as a regular application.

Step-by-Step Solution

Here's a step-by-step solution to resolve the issue:

  1. Open the mix.exs file in your text editor.
  2. Locate the included_applications list.
  3. Remove or comment out the line that includes the os_mon application:
# included_applications: [:os_mon]
  1. Save the changes to the mix.exs file.
  2. Run mix release again to verify that the issue is resolved.

Conclusion

In conclusion, the error ** (Mix) :os_mon is listed both as a regular application and as an included application is caused by a conflict between the regular applications and the included applications in the mix.exs file. By identifying the culprit, new_relic_agent, and removing the os_mon application from the included_applications list, we can resolve this issue and successfully run mix release in our application.

Additional Tips

To avoid this issue in the future, make sure to:

  • Carefully review the mix.exs file for any conflicts between regular applications and included applications.
  • Use the mix deps command to verify the dependencies and their versions.
  • Use the mix release command with the --verbose flag to get more detailed output and help diagnose issues.

Introduction

In our previous article, we explored the issue of included_applications: [:os_mon] causing a critical Mix error. We identified the culprit, new_relic_agent, and provided a step-by-step solution to resolve the issue. In this article, we will answer some frequently asked questions (FAQs) related to this topic.

Q&A

Q: What is the difference between regular applications and included applications in Elixir?

A: In Elixir, regular applications are applications that are explicitly listed in the mix.exs file under the applications section. They are compiled and started by the mix release. Included applications, on the other hand, are applications that are included in the mix release, but not explicitly listed in the mix.exs file. They are compiled and started by the mix release, but not as separate applications.

Q: Why is it causing a conflict to list os_mon as both a regular application and an included application?

A: When os_mon is listed as both a regular application and an included application, it causes a conflict because the mix release is trying to start it twice. This results in the error message ** (Mix) :os_mon is listed both as a regular application and as an included application.

Q: How do I know if I have a conflict between regular applications and included applications?

A: To check for conflicts, you can run the mix deps command and verify the dependencies and their versions. You can also use the mix release command with the --verbose flag to get more detailed output and help diagnose issues.

Q: Can I remove the os_mon application from the included_applications list without affecting my application's functionality?

A: Yes, you can remove the os_mon application from the included_applications list without affecting your application's functionality. However, if you need to use the os_mon application as a regular application, you should remove it from the included_applications list and add it to the applications list instead.

Q: What are some best practices to avoid conflicts between regular applications and included applications?

A: To avoid conflicts, make sure to:

  • Carefully review the mix.exs file for any conflicts between regular applications and included applications.
  • Use the mix deps command to verify the dependencies and their versions.
  • Use the mix release command with the --verbose flag to get more detailed output and help diagnose issues.
  • Avoid listing applications as both regular applications and included applications.

Q: Can I use the os_mon application as both a regular application and an included application?

A: No, you cannot use the os_mon application as both a regular application and an included application. This will cause a conflict and result in the error message ** (Mix) :os_mon is listed both as a regular application and as an included application.

Q: How do I troubleshoot issues related to conflicts between regular applications and included applications?

A: To troubleshoot issues, you can:

  • Run the mix deps command to verify the dependencies and their versions.
  • Use the mix release command with the --verbose` flag to get more detailed output and help diagnose issues.
  • Review the mix.exs file for any conflicts between regular applications and included applications.
  • Consult the Elixir documentation and community resources for help.

Conclusion

In conclusion, the included_applications: [:os_mon] causes critical Mix error is a common issue that can be resolved by identifying the culprit, new_relic_agent, and removing the os_mon application from the included_applications list. By following the step-by-step solution and best practices outlined in this article, you can avoid conflicts between regular applications and included applications and successfully run mix release in your Elixir application.