🐛 bug: Preserve session data map across resets #3968
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Note Other AI code review bot(s) detectedCodeRabbit has detected other AI code review bot(s) in this pull request and will avoid duplicating their findings in the review comments. This may lead to a less comprehensive review. WalkthroughReset now clears the existing session data map with Changes
Sequence Diagram(s)(omitted — changes are local memory-management and tests, not a multi-component control flow) Estimated code review effort🎯 3 (Moderate) | ⏱️ ~20 minutes Possibly related PRs
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Summary of ChangesHello @gaby, I'm Gemini Code Assist1! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed! This pull request optimizes the handling of session data maps by changing how they are reset. Instead of creating a new map each time, the existing map is now cleared, which allows its capacity to be retained. This change is particularly beneficial when these maps are managed within a pool, as it reduces memory allocations and improves overall efficiency. A new test case has been introduced to validate this behavior and prevent data leakage across map reuses. Highlights
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Code Review
This pull request introduces a performance optimization by using clear() to reset a session data map instead of reallocating it. This is a good change that preserves the map's capacity when objects are reused from a sync.Pool. The new regression test is thorough in verifying this behavior. I've added one comment with a suggestion to improve the robustness of the new test by restructuring it slightly, which should help prevent potential test flakiness.
middleware/session/data_test.go
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| func TestData_ResetReuseMap(t *testing.T) { | ||
| t.Parallel() | ||
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| t.Run("Reuse cleared map across pool cycles", func(t *testing.T) { | ||
| t.Parallel() | ||
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| d := acquireData() | ||
| originalPtr := mapPointer(d.Data) | ||
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| d.Set("key1", "value1") | ||
| d.Set("key2", "value2") | ||
| require.Equal(t, originalPtr, mapPointer(d.Data), "Expected map pointer to stay constant after writes") | ||
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| d.Reset() | ||
| require.Empty(t, d.Data, "Expected data map to be empty after reset") | ||
| require.Equal(t, originalPtr, mapPointer(d.Data), "Expected reset to preserve underlying map") | ||
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| d.Set("key3", "value3") | ||
| require.Nil(t, d.Get("key1"), "Expected cleared key not to leak after reset") | ||
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| d.Reset() | ||
| dataPool.Put(d) | ||
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| reused := acquireData() | ||
| t.Cleanup(func() { | ||
| reused.Reset() | ||
| dataPool.Put(reused) | ||
| }) | ||
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| require.Equal(t, originalPtr, mapPointer(reused.Data), "Expected pooled data to reuse cleared map") | ||
| require.Empty(t, reused.Data, "Expected pooled data to be empty after reuse") | ||
| require.Nil(t, reused.Get("key2"), "Expected no leakage of prior entries on reuse") | ||
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| reused.Set("key4", "value4") | ||
| require.Equal(t, "value4", reused.Get("key4"), "Expected pooled map to accept new values") | ||
| }) | ||
| } |
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This test combines verifying the Reset behavior with the sync.Pool reuse logic. This structure makes it difficult to ensure the acquired data object d is always returned to the pool if an assertion fails, as it's manually returned mid-test. A test failure before dataPool.Put(d) would leak the object, potentially causing flakiness in other parallel tests.
To improve robustness and clarity, consider splitting this into two more focused tests:
- A test to verify that
Resetclears the map while preserving the underlying allocation. - A separate test to verify that an object returned to the pool is correctly reused.
This separation makes each test's purpose clearer and allows for more straightforward resource management using t.Cleanup or defer.
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Pull request overview
This PR optimizes memory usage in the session middleware by replacing map reallocation with in-place clearing during reset operations. Instead of creating a new map with make(), the code now uses Go's clear() built-in (available since Go 1.21) to remove all entries while preserving the underlying map capacity.
Key Changes:
- Modified
Reset()method to clear map entries in-place rather than reallocating - Added comprehensive regression test to verify map reuse across pool cycles and prevent data leakage
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.
| File | Description |
|---|---|
| middleware/session/data.go | Changed Reset() to use clear(d.Data) instead of d.Data = make(map[any]any) to preserve map capacity |
| middleware/session/data_test.go | Added TestData_ResetReuseMap test and mapPointer helper to verify map pointer stability and proper clearing behavior across pool cycles |
Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## main #3968 +/- ##
==========================================
- Coverage 91.67% 91.59% -0.09%
==========================================
Files 119 119
Lines 10177 10194 +17
==========================================
+ Hits 9330 9337 +7
- Misses 536 543 +7
- Partials 311 314 +3
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Actionable comments posted: 1
📜 Review details
Configuration used: Repository UI
Review profile: CHILL
Plan: Pro
📒 Files selected for processing (1)
middleware/session/data_test.go
🧰 Additional context used
📓 Path-based instructions (2)
**/*_test.go
📄 CodeRabbit inference engine (AGENTS.md)
When adding Go tests, always invoke
t.Parallel()at the start of each test and subtest to maximize concurrency
Files:
middleware/session/data_test.go
**/*.go
📄 CodeRabbit inference engine (AGENTS.md)
Prefer
github.com/gofiber/utils/v2helpers (for example,utils.Trim) when performing common operations such as string manipulation, whenever it is practical and appropriate for the surrounding code
Files:
middleware/session/data_test.go
🧠 Learnings (8)
📓 Common learnings
Learnt from: sixcolors
Repo: gofiber/fiber PR: 3016
File: middleware/session/session.go:46-61
Timestamp: 2024-10-02T23:02:12.306Z
Learning: In this codebase, the `sessionPool` only contains `Session` instances, so type assertions without additional checks are acceptable.
Learnt from: sixcolors
Repo: gofiber/fiber PR: 3016
File: middleware/session/session.go:46-61
Timestamp: 2024-10-08T19:06:06.583Z
Learning: In this codebase, the `sessionPool` only contains `Session` instances, so type assertions without additional checks are acceptable.
📚 Learning: 2024-10-02T23:02:12.306Z
Learnt from: sixcolors
Repo: gofiber/fiber PR: 3016
File: middleware/session/session.go:46-61
Timestamp: 2024-10-02T23:02:12.306Z
Learning: In this codebase, the `sessionPool` only contains `Session` instances, so type assertions without additional checks are acceptable.
Applied to files:
middleware/session/data_test.go
📚 Learning: 2025-09-14T00:10:40.547Z
Learnt from: sixcolors
Repo: gofiber/fiber PR: 0
File: :0-0
Timestamp: 2025-09-14T00:10:40.547Z
Learning: The `session.Release()` method in the `middleware/session` package is responsible for returning the Session back to `sync.Pool` via `sessionPool.Put(s)`. It also calls Reset() to clear session data. Users must call Release() when done with the session, even after calling Save().
Applied to files:
middleware/session/data_test.go
📚 Learning: 2024-07-26T21:00:12.902Z
Learnt from: sixcolors
Repo: gofiber/fiber PR: 2922
File: middleware/cors/utils.go:63-71
Timestamp: 2024-07-26T21:00:12.902Z
Learning: The project uses the testify/assert package for assertions in unit tests.
Applied to files:
middleware/session/data_test.go
📚 Learning: 2024-10-08T19:06:06.583Z
Learnt from: sixcolors
Repo: gofiber/fiber PR: 3016
File: middleware/session/store.go:164-167
Timestamp: 2024-10-08T19:06:06.583Z
Learning: Unit tests in this project use testify require.
Applied to files:
middleware/session/data_test.go
📚 Learning: 2024-12-13T08:14:22.851Z
Learnt from: efectn
Repo: gofiber/fiber PR: 3162
File: hooks_test.go:228-228
Timestamp: 2024-12-13T08:14:22.851Z
Learning: In Go test files, prefer using the `require` methods from the `testify` package for assertions instead of manual comparisons and calls to `t.Fatal` or `t.Fatalf`.
Applied to files:
middleware/session/data_test.go
📚 Learning: 2025-10-16T07:19:52.418Z
Learnt from: grivera64
Repo: gofiber/fiber PR: 3807
File: adapter_test.go:118-144
Timestamp: 2025-10-16T07:19:52.418Z
Learning: In the Fiber codebase, the linter does not allow `require` assertions from within HTTP handlers (including net/http-style handlers). Use `t.Fatalf`, `t.Errorf`, or similar `testing.T` methods for error handling inside handler functions instead.
Applied to files:
middleware/session/data_test.go
📚 Learning: 2025-12-07T15:07:23.885Z
Learnt from: CR
Repo: gofiber/fiber PR: 0
File: AGENTS.md:0-0
Timestamp: 2025-12-07T15:07:23.885Z
Learning: Applies to **/*_test.go : When adding Go tests, always invoke `t.Parallel()` at the start of each test and subtest to maximize concurrency
Applied to files:
middleware/session/data_test.go
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- GitHub Check: unit (1.25.x, windows-latest)
🔇 Additional comments (2)
middleware/session/data_test.go (2)
4-4: LGTM: Necessary import for map pointer comparison.The
reflectimport is correctly added to support themapPointerhelper function used for verifying map identity across pool cycles.
238-240: LGTM: Clean reflection-based helper for map identity verification.The
mapPointerhelper correctly usesreflect.ValueOf(m).Pointer()to obtain the underlying map pointer, enabling precise verification that the same map instance is preserved across Reset operations and pool cycles.
Summary