Load function can be called multiple times for a single cache key before expiration #251
Description
This is related to #242, but the patch in #243 only partially fixed it. That patch makes sure that the load function can't be called twice for the same cache key at the same time, but doesn't do anything to prevent the load function from being called twice sequentially for the same cache key.
Steps for Reproduction
Here is a short standalone program to demonstrate the issue:
package main
import (
"context"
"fmt"
"os"
"time"
"runtime/debug"
"github.com/eko/gocache/lib/v4/cache"
gocacheStore "github.com/eko/gocache/store/go_cache/v4"
gocache "github.com/patrickmn/go-cache"
)
func main() {
// Verify dependency version
if bi, ok := debug.ReadBuildInfo(); ok {
for _, dep := range bi.Deps {
if dep.Path == "github.com/eko/gocache/lib/v4" {
fmt.Println(dep)
}
}
}
callCount := 0
loader := func(ctx context.Context, key any) (struct{}, error) {
fmt.Printf("loading cache for key %T %v\n", key, key)
callCount++
return struct{}{}, nil
}
cacheClient := gocache.New(5*time.Minute, 10*time.Minute)
cacheStore := gocacheStore.NewGoCache(cacheClient)
cache := cache.NewLoadable[struct{}](loader, cache.New[struct{}](cacheStore))
ctx := context.Background()
cache.Get(ctx, 1)
//time.Sleep(100 * time.Millisecond) // test passes if you uncomment this!
cache.Get(ctx, 1)
fmt.Printf("call count: got %v, want %v\n", callCount, 1)
if callCount != 1 {
os.Exit(1)
}
}&{github.com/eko/gocache/lib/v4 v4.1.6 h1:5WWIGISKhE7mfkyF+SJyWwqa4Dp2mkdX8QsZpnENqJI= <nil>}
loading cache for key int 1
loading cache for key int 1
call count: got 2, want 1
exit status 1
go.mod
module example.com/m
go 1.22
toolchain go1.22.3
require (
github.com/eko/gocache/lib/v4 v4.1.6
github.com/eko/gocache/store/go_cache/v4 v4.2.2
github.com/patrickmn/go-cache v2.1.0+incompatible
)
require (
github.com/beorn7/perks v1.0.1 // indirect
github.com/cespare/xxhash/v2 v2.1.2 // indirect
github.com/golang/mock v1.6.0 // indirect
github.com/golang/protobuf v1.5.2 // indirect
github.com/matttproud/golang_protobuf_extensions v1.0.1 // indirect
github.com/prometheus/client_golang v1.14.0 // indirect
github.com/prometheus/client_model v0.3.0 // indirect
github.com/prometheus/common v0.37.0 // indirect
github.com/prometheus/procfs v0.8.0 // indirect
golang.org/x/exp v0.0.0-20240416160154-fe59bbe5cc7f // indirect
golang.org/x/sync v0.7.0 // indirect
golang.org/x/sys v0.5.0 // indirect
google.golang.org/protobuf v1.33.0 // indirect
)
And here is a test case that you can add to loadable_test.go to reproduce it:
func TestLoadFuncOnlyCalledOnce(t *testing.T) {
ctrl := gomock.NewController(t)
ctx := context.Background()
cacheValue := struct{}{}
cache1 := NewMockSetterCacheInterface[any](ctrl)
cache1.EXPECT().Get(ctx, "my-key").Return(nil, errors.New("unable to find in cache 1"))
cache1.EXPECT().Get(ctx, "my-key").Return(nil, errors.New("unable to find in cache 1"))
cache1.EXPECT().Set(ctx, "my-key", cacheValue).AnyTimes().Return(nil)
callCount := 0
loadFunc := func(ctx context.Context, key any) (any, error) {
callCount++
return cacheValue, nil
}
cache := NewLoadable[any](loadFunc, cache1)
cache.Get(ctx, "my-key")
cache.Get(ctx, "my-key")
assert.Equal(t, callCount, 1)
}Or, comment out the time.Sleep(time.Millisecond * 10) in the existing test TestLoadableGetWhenAvailableInLoadFunc. Sleeping hides the bug!
Expected behavior
If cache.Get("my-key") is called, completes, and is called again before the cache entry expires, the loader should only be called once.
Actual behavior
The loader can be called many times.
Platforms
Tested on both Linux and macOS; I see the same bug in both places.
Versions
github.com/eko/gocache/lib/v4 v4.1.6 h1:5WWIGISKhE7mfkyF+SJyWwqa4Dp2mkdX8QsZpnENqJI=