Changes to the dependencies

Oct 13, 2025 by pynkocean.com 57 views

mix --verbose/MIX_DEBUG=1 does not output enough to understand why the cache is being spoiled

Understanding the Issue

When working with Elixir and the Mix build tool, it's not uncommon to encounter issues with the build cache. One such issue is cache spoliation, where the cache is unexpectedly invalidated, leading to slower build times and potential errors. In this article, we'll explore the issue of cache spoliation and how to use the --verbose and MIX_DEBUG=1 options to gain a better understanding of what's happening.

Elixir and Erlang/OTP Versions

Before we dive into the issue, let's take a look at the Elixir and Erlang/OTP versions we're using:

### Elixir and Erlang/OTP versions

$ elixir -v Erlang/OTP 27 [erts-15.2.2] [source] [64-bit] [smp:11:11] [ds:11:11:10] [async-threads:1] [jit]

Elixir 1.18.2 (compiled with Erlang/OTP 27)


**Operating System**

We're using macOS (N/A) as our operating system.

**Current Behavior**

I was experiencing build cache spoliation due to unknowingly using different versions of Elixir to compile a large codebase. Neither `MIX_DEBUG=1` nor `--verbose` helped understand why the cache was being spoiled.

**Expected Behavior**

It would be nice if `--verbose` or some other option could be used to understand why the cache was being spoiled. IMO if `--verbose` is being used and the cache is spoiled the output should prominently state why.

**Using `--verbose` and `MIX_DEBUG=1`**

To gain a better understanding of what's happening with the cache, we can use the `--verbose` and `MIX_DEBUG=1` options. Here's an example of how to use them:

```bash
mix --verbose --debug

However, as we've seen, this doesn't provide enough information to understand why the cache is being spoiled.

Why --verbose and MIX_DEBUG=1 aren't enough

So, why aren't --verbose and MIX_DEBUG=1 enough to understand why the cache is being spoiled? The answer lies in the way Mix handles the build cache.

When Mix builds a project, it uses a cache to store the results of previous builds. This cache is stored in a directory called .mix-cache. When Mix builds a project, it checks the cache to see if the results of the previous build are still valid. If they are, it uses the cached results instead of rebuilding the project from scratch.

However, if the cache is spoiled, Mix will rebuild the project from scratch, which can be time-consuming and potentially error-prone.

What's causing the cache to be spoiled?

So, what's causing the cache to be spoiled? There are several reasons why this might happen:

Different Elixir versions: If you're using different versions of Elixir to compile your project, the cache will be spoiled.
Changes to the project: If you make changes to the project, the cache will be spoiled.
Changes to the dependencies: If you make changes to the dependencies of your project, the cache will be spoiled.

How to fix the issue

So, how can you fix the issue of cache spoliation? Here are a few suggestions:

Use a consistent Elixir version: Make sure you're using the same version of Elixir to compile your project.
Use a consistent cache directory: Make sure you're using the same cache directory for all builds.
Use a cache invalidation strategy: Consider using a cache invalidation strategy to ensure that the cache is updated regularly.

Conclusion

In conclusion, the --verbose and MIX_DEBUG=1 options aren't enough to understand why the cache is being spoiled. However, by understanding the reasons why the cache is being spoiled, you can take steps to fix the issue and improve the performance of your builds.

Additional Resources

If you're interested in learning more about the Elixir build tool and how to use it effectively, here are some additional resources:

Elixir documentation: The official Elixir documentation provides a wealth of information on how to use the Elixir build tool.
Mix documentation: The official Mix documentation provides a wealth of information on how to use the Mix build tool.
Elixir community: The Elixir community is a great resource for learning more about Elixir and how to use it effectively.

FAQs

Here are some frequently asked questions about the Elixir build tool and how to use it effectively:

Q: Why is my cache being spoiled? A: Your cache is being spoiled because of changes to the project, dependencies, or Elixir version.
Q: How can I fix the issue of cache spoliation? A: You can fix the issue of cache spoliation by using a consistent Elixir version, cache directory, and cache invalidation strategy.
Q: What are some best practices for using the Elixir build tool? A: Some best practices for using the Elixir build tool include using a consistent Elixir version, cache directory, and cache invalidation strategy.
mix --verbose/MIX_DEBUG=1 does not output enough to understand why the cache is being spoiled

Q&A: Understanding and Fixing Cache Spoliation in Elixir

Q: What is cache spoliation in Elixir?

A: Cache spoliation in Elixir refers to the unexpected invalidation of the build cache, leading to slower build times and potential errors.

Q: Why is my cache being spoiled?

A: Your cache is being spoiled because of changes to the project, dependencies, or Elixir version. This can include:

Different Elixir versions: If you're using different versions of Elixir to compile your project, the cache will be spoiled.
Changes to the project: If you make changes to the project, the cache will be spoiled.
Changes to the dependencies: If you make changes to the dependencies of your project, the cache will be spoiled.

Q: How can I fix the issue of cache spoliation?

A: You can fix the issue of cache spoliation by using a consistent Elixir version, cache directory, and cache invalidation strategy. Here are some steps you can take:

Use a consistent Elixir version: Make sure you're using the same version of Elixir to compile your project.
Use a consistent cache directory: Make sure you're using the same cache directory for all builds.
Use a cache invalidation strategy: Consider using a cache invalidation strategy to ensure that the cache is updated regularly.

Q: What are some best practices for using the Elixir build tool?

A: Some best practices for using the Elixir build tool include:

Use a consistent Elixir version: Make sure you're using the same version of Elixir to compile your project.
Use a consistent cache directory: Make sure you're using the same cache directory for all builds.
Use a cache invalidation strategy: Consider using a cache invalidation strategy to ensure that the cache is updated regularly.
Monitor your build cache: Keep an eye on your build cache to ensure that it's not being spoiled unnecessarily.

Q: How can I troubleshoot cache spoliation issues?

A: To troubleshoot cache spoliation issues, you can try the following:

Check your Elixir version: Make sure you're using the same version of Elixir to compile your project.
Check your cache directory: Make sure you're using the same cache directory for all builds.
Check your dependencies: Make sure your dependencies are up to date and not causing any issues.
Use the --verbose and MIX_DEBUG=1 options: Use these options to get more information about what's happening with your build cache.

Q: What are some common mistakes that can cause cache spoliation?

A: Some common mistakes that can cause cache spoliation include:

Using different Elixir versions: Using different versions of Elixir to compile your project can cause cache spoliation.
Making changes to the project: Making changes to the project can cause cache spoliation.
Making changes to the dependencies: Making changes to the dependencies of your project can cause cache spoliation.

Q: How can I prevent cache spoliation in the future?

A: To prevent cache spoliation in the future, you can try the following:

Use a consistent Elixir version: Make sure you're using the same version of Elixir to compile your project.
Use a consistent cache directory: Make sure you're using the same cache directory for all builds.
Use a cache invalidation strategy: Consider using a cache invalidation strategy to ensure that the cache is updated regularly.
Monitor your build cache: Keep an eye on your build cache to ensure that it's not being spoiled unnecessarily.

Conclusion

In conclusion, cache spoliation in Elixir can be a frustrating issue, but by understanding the reasons why it's happening and taking steps to fix it, you can improve the performance of your builds and reduce the risk of errors. By following the best practices outlined in this article, you can prevent cache spoliation and ensure that your builds are fast and reliable.