Add In_WSL function to check whether the host runs on WSL #12799

paolosalvatori · 2025-06-25T16:07:33Z

Motivation

On Windows 11 + WSL, you have a layered setup:

Windows 11 Host: Your primary operating system.
WSL 2: A lightweight virtual machine running a Linux kernel. Docker Desktop runs its daemon inside this WSL 2 VM.
Docker Container: Your Azurite container is running inside the Docker daemon's environment, which itself is in the WSL 2 VM.

The IP address of the Azurite container under NetworkSettings.Networks.bridge.IPAddress, let's say 172.17.02, is the IP address of your Azurite container within the Docker bridge network.

This IP is only directly routable from other containers on the same Docker bridge network or from the Docker host itself (which, in this case, is the WSL 2 VM). Now, usually Docker on Windows is installed on a separate distro. You can check this by running the following command from the Windows command-prompt:

wsl --list --running

This should return something like this:

Windows Subsystem for Linux Distributions:
Ubuntu-24.04 (Default)
docker-desktop

As you can see, there are two distros: Ubuntu-24.04 (Default) running WSL, and docker-desktop. So far so good? Perfect. When running localhost in host mode in the WSL 2 distro's shell and not inside another Docker container, cannot use the IP address of the Azurite container. Full stop.

So I extended the localstack.config class with a function to understand whether the host is running on WSL:

def is_wsl() -> bool:
    return platform.system().lower() == "linux" and os.environ.get("WSL_DISTRO_NAME") is not None

Changes

I extended the localstack.config class with a function to understand whether the host is running on WSL:

def is_wsl() -> bool:
    return platform.system().lower() == "linux" and os.environ.get("WSL_DISTRO_NAME") is not None

Testing

On WSL the is_wsl() returns true.

Introduced dynamic port allocation for Azurite containers using available TCP ports, replacing fixed port mappings. Added detection for WSL environments to adjust host settings for improved compatibility. Enhanced request proxying with detailed logging and error handling for robust communication.

localstack-bot · 2025-06-25T16:07:44Z

All contributors have signed the CLA ✍️ ✅
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localstack-bot

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paolosalvatori · 2025-06-25T16:09:41Z

I have read the CLA Document and I hereby sign the CLA

github-actions · 2025-06-25T16:10:12Z

Test Results - Preflight, Unit

21 727 tests ±0 20 070 ✅ ±0 6m 14s ⏱️ +3s
1 suites ±0 1 657 💤 ±0
1 files ±0 0 ❌ ±0

Results for commit e77b206. ± Comparison against base commit 3d56935.

♻️ This comment has been updated with latest results.

github-actions · 2025-06-25T16:18:05Z

S3 Image Test Results (AMD64 / ARM64)

2 files 2 suites 8m 55s ⏱️
512 tests 462 ✅ 50 💤 0 ❌
1 024 runs 924 ✅ 100 💤 0 ❌

Results for commit e77b206.

♻️ This comment has been updated with latest results.

github-actions · 2025-06-25T17:11:09Z

LocalStack Community integration with Pro

2 files ±0 2 suites ±0 1h 45m 50s ⏱️ + 1m 0s
4 896 tests +2 4 122 ✅ +2 774 💤 ±0 0 ❌ ±0
4 898 runs +2 4 122 ✅ +2 776 💤 ±0 0 ❌ ±0

Results for commit e77b206. ± Comparison against base commit 3d56935.

♻️ This comment has been updated with latest results.

thrau

hey @paolosalvatori! thanks for being a WSL champion :-) we have few users on windows, but this may change with the growing azure team.

just two minor things:

do we need the solutions file checked into the repo? we normally don't check in environment-specific files
a more descriptive PR title for the commit history would be great ;-)

alexrashed

From your PR description, I can see that you are fighting with a pretty specific issue (running LocalStack in host mode - for development purposes). I am wondering if there is a more generic way to solve the Docker networking issue you might be facing.
Maybe @simonrw or @dfangl could have an idea here?

However, the implementation is looking good, and with Mac, Linux, and WSL, most host systems are covered, so it's also fair to keep the function as is.
The sln file should be removed though before merging this PR.

localstack.sln

localstack-core/localstack/config.py

paolosalvatori · 2025-06-26T11:17:15Z

hey @paolosalvatori! thanks for being a WSL champion :-) we have few users on windows, but this may change with the growing azure team.

just two minor things:

do we need the solutions file checked into the repo? we normally don't check in environment-specific files

a more descriptive PR title for the commit history would be great ;-)

I think I filed the PR from PyCharm to make an experiment, and I forgot to change the title to something meaningful. I think PyCharm turned the name of the branch paolo_in_wsl into the PR name 😄 I usually use very descriptive titles in my PRs.

Regarding the .sln file, I had the same issue on the other PR I opened on localstack-ext: I originally followed the instructions from Getting Started – Setting up a Development Environment for LocalStack Core on Notion and initially used Visual studio Code, then I switched to PyCharm. The .sln file was added by Visual studio Code. I removed the .sln file from the PR and added *.sln to .gitignore.

alexrashed

Thanks for jumping on the comments and answering the questions! The code is simple and lookin' good :)

paolosalvatori · 2025-06-26T11:36:50Z

Thanks @alexrashed 🙂 @thrau when you have time, please give your approval, so I can unblock the other PR on localstack-ext repo as linting test fails saying that is_in_wsl attribute is not in localstack.config module 🙂 Thanks! 🙏

thomaschaaf · 2025-06-26T11:39:13Z

@paolosalvatori I believe you mentioned the wrong person on your request. 🙃

paolosalvatori · 2025-06-26T11:41:02Z

@paolosalvatori I believe you mentioned the wrong person on your request. 🙃

Yep, wrong Thomas 🙂 I trusted GitHub when it proposed your alias instead of Thomas Rausch one 🙂

alexrashed · 2025-06-26T12:10:02Z

@paolosalvatori You already have the approval from my side (@thrau needs to approve still though).
But you also do have linting errors here in the project.
Please make sure to fix those and configure the pre-commit hook (to check this before pushing a commit) to avoid issues like this in the future.

paolosalvatori · 2025-06-26T12:39:49Z

@alexrashed thanks for the heads up. I ran pre-commit install on both localstack and localstack-ext projects and I fixed the linting issue affecting this PR. I know that you approved the PR 🙏 but Thomas approval is pending. He requested a change, so the PR cannot be merged until he approves it.

github-actions · 2025-06-26T12:57:14Z

Test Results (amd64) - Acceptance

7 tests ±0 5 ✅ ±0 3m 8s ⏱️ ±0s
1 suites ±0 2 💤 ±0
1 files ±0 0 ❌ ±0

Results for commit e77b206. ± Comparison against base commit 3d56935.

github-actions · 2025-06-26T13:30:43Z

Test Results (amd64) - Integration, Bootstrap

5 files 5 suites 2h 22m 52s ⏱️
5 253 tests 4 327 ✅ 926 💤 0 ❌
5 259 runs 4 327 ✅ 932 💤 0 ❌

Results for commit e77b206.

thrau

LGTM!

paolosalvatori added 2 commits June 25, 2025 16:33

Added in_wsl function to check whether the host runs on WSL

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paolosalvatori requested a review from thrau as a code owner June 25, 2025 16:07

localstack-bot reviewed Jun 25, 2025

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localstack-bot added a commit that referenced this pull request Jun 25, 2025

@paolosalvatori has signed the CLA in #12799

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thrau requested changes Jun 26, 2025

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alexrashed reviewed Jun 26, 2025

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paolosalvatori changed the title ~~Paolo in wsl~~ Add In_WSL function to check whether the host runs on WSL Jun 26, 2025

Remove accidentally committed .sln file

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alexrashed approved these changes Jun 26, 2025

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Fixed linting

e77b206

paolosalvatori added semver: minor Non-breaking changes which can be included in minor releases, but not in patch releases labels Jun 26, 2025

paolosalvatori added this to the 4.6 milestone Jun 26, 2025

thrau approved these changes Jun 26, 2025

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paolosalvatori merged commit 019d5ec into master Jun 26, 2025
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paolosalvatori deleted the paolo_in_wsl branch June 26, 2025 14:39

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Add In_WSL function to check whether the host runs on WSL #12799

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