Loader2 #3
Loader2 #3
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WalkthroughA backend loader feature was introduced to the cache implementation, allowing cache misses to trigger a fetch from a backend source. The documentation was updated to describe this feature and provide usage examples. New code defines the loader logic, integrates it with the cache, and adds tests to verify correct loader and cache behavior. Changes
Sequence Diagram(s)sequenceDiagram
participant Client
participant CacheWithLoader
participant Cache
participant Backend
Client->>CacheWithLoader: Get(key)
alt Loader is set
CacheWithLoader->>Backend: loader(key)
alt Value found in backend
Backend-->>CacheWithLoader: value, true
CacheWithLoader->>Cache: Set(key, value)
CacheWithLoader-->>Client: value, true
else Value not found
Backend-->>CacheWithLoader: zero, false
CacheWithLoader->>Cache: Get(key)
alt Value in cache
Cache-->>CacheWithLoader: value, true
CacheWithLoader-->>Client: value, true
else Not found
Cache-->>CacheWithLoader: zero, false
CacheWithLoader-->>Client: zero, false
end
end
else Loader not set
CacheWithLoader->>Cache: Get(key)
Cache-->>CacheWithLoader: value, found
CacheWithLoader-->>Client: value, found
end
Estimated code review effort2 (~18 minutes) Poem
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Actionable comments posted: 1
🧹 Nitpick comments (1)
loader.go (1)
46-46: Remove unnecessary blank line.There's an extra blank line that should be removed for cleaner code formatting.
-
📜 Review details
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Review profile: CHILL
Plan: Pro
📒 Files selected for processing (3)
README.md(3 hunks)loader.go(1 hunks)loader_test.go(1 hunks)
🧬 Code Graph Analysis (2)
loader_test.go (1)
loader.go (1)
NewWithLoader(14-24)
loader.go (1)
cache.go (2)
Cache(12-24)New(26-42)
🧰 Additional context used
🧬 Code Graph Analysis (2)
loader_test.go (1)
loader.go (1)
NewWithLoader(14-24)
loader.go (1)
cache.go (2)
Cache(12-24)New(26-42)
🔇 Additional comments (11)
README.md (3)
14-14: LGTM: Clear and concise feature description.The addition to the features list accurately describes the new backend loading capability.
24-25: Good organization with section headers.Adding section headers improves readability and helps users navigate between basic usage and advanced features.
58-99: Comprehensive usage example with proper error handling.The backend loader example demonstrates practical database integration and follows Go best practices with proper error handling and resource cleanup using
defer db.Close().loader_test.go (5)
7-24: Well-structured test setup.The test properly sets up an in-memory backend and loader function, creating a realistic testing scenario.
26-33: Good coverage of backend loading scenario.This test case correctly verifies that values can be loaded from the backend when not present in the cache.
35-45: Excellent validation of caching behavior.The test cleverly verifies that loaded values are cached by removing the key from the backend and confirming the value remains accessible from the cache.
47-51: Proper handling of non-existent keys.This test case correctly verifies the behavior when a key exists in neither the cache nor the backend.
53-67: Important test for cache precedence over loader.This test case validates that cached values take precedence over the loader, which is critical for performance and correctness.
loader.go (3)
3-5: Clear and well-documented function type.The LoaderFunc type definition is clean and the documentation clearly explains the return values.
7-11: Appropriate struct design using embedding.The CacheWithLoader struct effectively extends the base Cache functionality through embedding, following Go idioms.
13-24: Solid constructor with proper error propagation.The NewWithLoader function correctly delegates to the base cache constructor and properly propagates any errors.
| func (cl *CacheWithLoader[K, V]) Get(key K) (V, bool) { | ||
|
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||
| // If not in cache, try to load from backend | ||
| if cl.loader != nil { | ||
| value, found := cl.loader(key) | ||
| if found { | ||
| // Store the loaded value in the cache | ||
| cl.Cache.Set(key, value) | ||
| return value, true | ||
| } | ||
| } | ||
|
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| // Try to get from cache first | ||
| value, found := cl.Cache.Get(key) | ||
| if found { | ||
| return value, true | ||
| } | ||
|
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| // Return zero value if not found | ||
| var zero V | ||
| return zero, false | ||
| } No newline at end of file |
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Critical issue: Incorrect order of operations in Get method.
The current implementation checks the loader before checking the cache, which defeats the purpose of caching and will cause performance issues. The cache should be checked first, and the loader should only be called on cache misses.
Apply this diff to fix the logic:
func (cl *CacheWithLoader[K, V]) Get(key K) (V, bool) {
+ // Try to get from cache first
+ value, found := cl.Cache.Get(key)
+ if found {
+ return value, true
+ }
// If not in cache, try to load from backend
if cl.loader != nil {
value, found := cl.loader(key)
if found {
// Store the loaded value in the cache
cl.Cache.Set(key, value)
return value, true
}
}
- // Try to get from cache first
- value, found := cl.Cache.Get(key)
- if found {
- return value, true
- }
-
-
// Return zero value if not found
var zero V
return zero, false
}📝 Committable suggestion
‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.
| func (cl *CacheWithLoader[K, V]) Get(key K) (V, bool) { | |
| // If not in cache, try to load from backend | |
| if cl.loader != nil { | |
| value, found := cl.loader(key) | |
| if found { | |
| // Store the loaded value in the cache | |
| cl.Cache.Set(key, value) | |
| return value, true | |
| } | |
| } | |
| // Try to get from cache first | |
| value, found := cl.Cache.Get(key) | |
| if found { | |
| return value, true | |
| } | |
| // Return zero value if not found | |
| var zero V | |
| return zero, false | |
| } | |
| func (cl *CacheWithLoader[K, V]) Get(key K) (V, bool) { | |
| // Try to get from cache first | |
| value, found := cl.Cache.Get(key) | |
| if found { | |
| return value, true | |
| } | |
| // If not in cache, try to load from backend | |
| if cl.loader != nil { | |
| value, found := cl.loader(key) | |
| if found { | |
| // Store the loaded value in the cache | |
| cl.Cache.Set(key, value) | |
| return value, true | |
| } | |
| } | |
| // Return zero value if not found | |
| var zero V | |
| return zero, false | |
| } |
🤖 Prompt for AI Agents
In loader.go around lines 28 to 50, the Get method incorrectly calls the loader
before checking the cache, which undermines caching efficiency. To fix this,
first attempt to retrieve the value from the cache using cl.Cache.Get; if found,
return it immediately. Only if the cache lookup fails, call cl.loader to load
the value, store it in the cache if found, and then return it. This ensures the
cache is prioritized and the loader is used only on cache misses.
Summary by CodeRabbit
New Features
Documentation
Tests