docs(`terraform_validate`): Describe that paralelsim is safe to use with tofu 1.10+ #957

MaxymVlasov · 2026-01-23T15:00:45Z

Follow-up to #956
Relates to #640

tofu 1.10+

coderabbitai · 2026-01-23T15:01:05Z

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📝 Walkthrough

Summary by CodeRabbit

Documentation
- Clarified that a race-condition affecting the plugin cache was fixed in OpenToFu v1.10+, so parallelism can be used safely again.
- Minor formatting adjustment to the README for improved readability.

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Walkthrough

Documentation update to README.md clarifying that the TF_PLUGIN_CACHE_DIR race-condition was resolved in OpenToFu v1.10+, making parallelism safe again; also a minor explicit line-break formatting adjustment.

Changes

Cohort / File(s)	Summary
Documentation update `README.md`	Added clarification in `terraform_validate` section that the `TF_PLUGIN_CACHE_DIR` race-condition was fixed in OpenToFu v1.10+, restoring parallelism safety; added an explicit line-break formatting tweak.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

Suggested reviewers

antonbabenko
yermulnik

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly indicates a documentation update for terraform_validate regarding parallelism safety with tofu 1.10+, which matches the actual changeset.
Description check	✅ Passed	The description provides context by referencing related PR `#956` and issue `#640`, connecting the change to the broader codebase discussions about this feature.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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Copilot

Pull request overview

This PR updates the documentation for the terraform_validate hook to clarify that parallelism is safe to use with OpenTofu v1.10+, which has resolved the race condition issues present in earlier versions when using TF_PLUGIN_CACHE_DIR.

Changes:

Added documentation noting that OpenTofu v1.10+ has fixed the parallelism race condition issue with the global provider cache

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README.md

Copilot · 2026-01-23T15:02:30Z

README.md

 > [!IMPORTANT]
-> If you use [`TF_PLUGIN_CACHE_DIR`](https://developer.hashicorp.com/terraform/cli/config/config-file#provider-plugin-cache), we recommend enabling `--hook-config=--retry-once-with-cleanup=true` or disabling parallelism (`--hook-config=--parallelism-limit=1`) to avoid [race conditions when `terraform init` writes to it](https://github.com/hashicorp/terraform/issues/31964).
+> If you use [`TF_PLUGIN_CACHE_DIR`](https://developer.hashicorp.com/terraform/cli/config/config-file#provider-plugin-cache), we recommend enabling `--hook-config=--retry-once-with-cleanup=true` or disabling parallelism (`--hook-config=--parallelism-limit=1`) to avoid [race conditions when `terraform init` writes to it](https://github.com/hashicorp/terraform/issues/31964).  
+> This [issue was fixed in OpenToFu v1.10+](https://opentofu.org/blog/help-us-test-opentofu-1-10-0-alpha2/#global-provider-cache-locking), so it's safe to use parallelism with it.


Typo: "OpenToFu" should be "OpenTofu" (missing the second 'o').

coderabbitai

Actionable comments posted: 1

🤖 Fix all issues with AI agents

In `@README.md`:
- Around line 972-974: Update the [!IMPORTANT] block that currently links to the
OpenTofu alpha2 blog: replace the alpha blog URL with the official OpenTofu
v1.10.0 release notes (and/or the stable beta release notes) URL, change the
wording to reference the official v1.10.0 release notes instead of the alpha
blog, and append a note recommending v1.10.5+ if users still see lock contention
errors when using concurrent cache access; target the markdown block starting
with the [!IMPORTANT] marker and the sentence mentioning "This [issue was fixed
in OpenTofu v1.10+]" to make these edits.

coderabbitai · 2026-01-23T15:04:26Z

README.md

 > [!IMPORTANT]
-> If you use [`TF_PLUGIN_CACHE_DIR`](https://developer.hashicorp.com/terraform/cli/config/config-file#provider-plugin-cache), we recommend enabling `--hook-config=--retry-once-with-cleanup=true` or disabling parallelism (`--hook-config=--parallelism-limit=1`) to avoid [race conditions when `terraform init` writes to it](https://github.com/hashicorp/terraform/issues/31964).
+> If you use [`TF_PLUGIN_CACHE_DIR`](https://developer.hashicorp.com/terraform/cli/config/config-file#provider-plugin-cache), we recommend enabling `--hook-config=--retry-once-with-cleanup=true` or disabling parallelism (`--hook-config=--parallelism-limit=1`) to avoid [race conditions when `terraform init` writes to it](https://github.com/hashicorp/terraform/issues/31964).  
+> This [issue was fixed in OpenToFu v1.10+](https://opentofu.org/blog/help-us-test-opentofu-1-10-0-alpha2/#global-provider-cache-locking), so it's safe to use parallelism with it.


⚠️ Potential issue | 🟡 Minor

🧩 Analysis chain

🌐 Web query:

OpenTofu v1.10 release notes global provider cache locking fix

💡 Result:

In the OpenTofu v1.10.x release line, the “global provider cache locking” change and the later “locking fix” show up as:

v1.10.0 (prereleases / beta notes): the shared provider cache controlled by TF_PLUGIN_CACHE_DIR gained filesystem-level locking so concurrent OpenTofu runs (e.g., many parallel tofu init in CI) don’t clobber the cache. [2]

v1.10.5 (bugfix): fixed an issue where using TF_PLUGIN_CACHE_DIR could cause unexpected lock contention errors (GitHub issue/PR #3090). Release notes also remind users it’s still recommended to have valid .terraform.lock.hcl files when using TF_PLUGIN_CACHE_DIR. [1]

Sources: [1] (newreleases.io) [2] (opentofu.org)

Citations:

1: https://newreleases.io/project/github/opentofu/opentofu/release/v1.10.5?utm_source=openai

2: https://opentofu.org/blog/help-us-test-opentofu-1-10-0-beta1/?utm_source=openai

🌐 Web query:

OpenTofu v1.10 final release TF_PLUGIN_CACHE_DIR race condition

💡 Result:

OpenTofu v1.10.0 (final) is the release line that addresses the long-standing race condition / unsafeness of sharing TF_PLUGIN_CACHE_DIR across concurrent tofu init runs by adding filesystem-level locking around the shared provider plugin cache (“Global Provider Cache Lock”), making concurrent operations (CI, Terragrunt, parallel pipelines) safe in the intended design. [1], [2], [3]

Notes/caveats from the v1.10 series:

The underlying problem was tracked as “provider plugin cache is not safe to access concurrently” (race during concurrent installs into the cache). [1]

The locking work landed during the 1.10.0 prereleases and is described as making the cache safe for concurrent OpenTofu operations. [2], [3]

There were still follow-on issues in the 1.10 patch line (e.g., “unexpected lock contention errors”) that were later fixed (example: v1.10.5 notes). [4]

Practical takeaway: If you’re asking whether v1.10.0 is the version where TF_PLUGIN_CACHE_DIR becomes concurrency-safe (i.e., the race condition is addressed), yes—that change is part of OpenTofu 1.10; and if you hit locking-related errors, upgrade within the 1.10.x line (at least past fixes like 1.10.5). [2], [4]

Sources: [1] GitHub issue, [2] OpenTofu 1.10.0-beta1 blog, [3] OpenTofu 1.10.0-alpha2 blog, [4] v1.10.5 changelog excerpt.

Link to the official OpenTofu v1.10.0 release notes instead of the alpha blog.

The alpha2 blog post documents the fix, but OpenTofu's official v1.10.0 release notes or the beta blog would be a more stable reference. Additionally, note that v1.10.5+ is recommended if users encounter lock contention errors during concurrent cache access.

🤖 Prompt for AI Agents

In `@README.md` around lines 972 - 974, Update the [!IMPORTANT] block that currently links to the OpenTofu alpha2 blog: replace the alpha blog URL with the official OpenTofu v1.10.0 release notes (and/or the stable beta release notes) URL, change the wording to reference the official v1.10.0 release notes instead of the alpha blog, and append a note recommending v1.10.5+ if users still see lock contention errors when using concurrent cache access; target the markdown block starting with the [!IMPORTANT] marker and the sentence mentioning "This [issue was fixed in OpenTofu v1.10+]" to make these edits.

yermulnik

LGMT apart from OpenTofu naming typo.

README.md

Co-authored-by: George Yermulnik (Georgii Iermulnik) <yz@yz.kiev.ua>

docs(terraform_validate): Describe that paralelsim is safe to use with

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tofu 1.10+

MaxymVlasov requested review from antonbabenko and yermulnik as code owners January 23, 2026 15:00

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Copilot started reviewing on behalf of MaxymVlasov January 23, 2026 15:01 View session

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Update README.md

9c7b53e

Co-authored-by: George Yermulnik (Georgii Iermulnik) <yz@yz.kiev.ua>

MaxymVlasov dismissed yermulnik’s stale review via 9c7b53e January 25, 2026 01:34

MaxymVlasov enabled auto-merge (squash) January 25, 2026 01:34

MaxymVlasov requested a review from yermulnik January 25, 2026 01:34

yermulnik approved these changes Jan 25, 2026

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MaxymVlasov merged commit 4692c17 into master Jan 25, 2026
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MaxymVlasov deleted the docs/tofu branch January 25, 2026 12:59

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docs(`terraform_validate`): Describe that paralelsim is safe to use with tofu 1.10+ #957

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