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feat: support periodic preload #63

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94 changes: 63 additions & 31 deletions config.go
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Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@
package hot

import (
"errors"
"context"
"time"

"github.com/samber/hot/pkg/base"
Expand Down Expand Up @@ -67,7 +67,8 @@ type HotCacheConfig[K comparable, V any] struct {
cacheName string
collectors []metrics.Collector

warmUpFn func() (map[K]V, []K, error)
preloadFn func() (map[K]V, []K, error)
preloadPeriod time.Duration
loaderFns LoaderChain[K, V]
revalidationLoaderFns LoaderChain[K, V]
revalidationErrorPolicy revalidationErrorPolicy
Expand Down Expand Up @@ -140,37 +141,45 @@ func (cfg HotCacheConfig[K, V]) WithSharding(nbr uint64, fn sharded.Hasher[K]) H
return cfg
}

// WithWarmUp preloads the cache with data from the provided function.
// This is useful for initializing the cache with frequently accessed data.
func (cfg HotCacheConfig[K, V]) WithWarmUp(fn func() (map[K]V, []K, error)) HotCacheConfig[K, V] {
cfg.warmUpFn = fn
// WithPreload loads the cache with data from the provided loader.
// This is useful for eagerly set the cache with frequently access data.
func (cfg HotCacheConfig[K, V]) WithPreload(preloader Preloader[K, V]) HotCacheConfig[K, V] {
if preloader.Timeout > 0 {
cfg.preloadFn = func() (map[K]V, []K, error) {
done := make(chan struct{}, 1)

var result map[K]V
var missing []K
var err error

go func() {
result, missing, err = preloader.Fn()
done <- struct{}{}
close(done)
}()

select {
case <-time.After(preloader.Timeout):
return nil, nil, context.DeadlineExceeded
case <-done:
return result, missing, err
}
}
} else {
cfg.preloadFn = preloader.Fn
}
cfg.preloadPeriod = preloader.Period
return cfg
}

// WithWarmUpWithTimeout preloads the cache with data from the provided function with a timeout.
// This is useful when the inner callback does not have its own timeout strategy.
// Deprecated: Use [HotCacheConfig.WithPreload] instead.
func (cfg HotCacheConfig[K, V]) WithWarmUp(fn func() (map[K]V, []K, error)) HotCacheConfig[K, V] {
return cfg.WithPreload(Preloader[K, V]{Fn: fn})
}

// Deprecated: Use [HotCacheConfig.WithPreload] instead.
func (cfg HotCacheConfig[K, V]) WithWarmUpWithTimeout(timeout time.Duration, fn func() (map[K]V, []K, error)) HotCacheConfig[K, V] {
cfg.warmUpFn = func() (map[K]V, []K, error) {
done := make(chan struct{}, 1)

var result map[K]V
var missing []K
var err error

go func() {
result, missing, err = fn()
done <- struct{}{}
close(done)
}()

select {
case <-time.After(timeout):
return nil, nil, errors.New("WarmUp timeout")
case <-done:
return result, missing, err
}
}
return cfg
return cfg.WithPreload(Preloader[K, V]{Fn: fn, Timeout: timeout})
}

// WithoutLocking disables mutex for the cache and improves internal performance.
Expand Down Expand Up @@ -267,9 +276,14 @@ func (cfg HotCacheConfig[K, V]) Build() *HotCache[K, V] {
cfg.collectors,
)

if cfg.warmUpFn != nil {
if cfg.preloadFn != nil {
hot.preloadFn = cfg.preloadFn
// @TODO: Check error?
hot.WarmUp(cfg.warmUpFn) //nolint:errcheck
hot.Preload(cfg.preloadFn) //nolint:errcheck

if cfg.preloadPeriod > 0 {
hot.StartPeriodicPreload(cfg.preloadPeriod)
}
}

if cfg.janitorEnabled {
Expand Down Expand Up @@ -299,3 +313,21 @@ func (cfg *HotCacheConfig[K, V]) buildPrometheusCollector(mode base.CacheMode) f
return collector
}
}

// Preloader holds the configuration for preloading the cache.
type Preloader[K comparable, V any] struct {
// Fn is the function that returns the data to preload into the cache.
// It returns a map of key-value pairs to load, a list of missing keys, and
// an error if any.
Fn func() (map[K]V, []K, error)

// Timeout is an optional duration to limit how long the preload function
// can run.
// If zero, no timeout is applied.
Timeout time.Duration

// Period is an optional duration for periodic cache refresh.
// If set, the perload function will be called repeatedly at this interval
// to refresh the cache.
Period time.Duration
}
92 changes: 64 additions & 28 deletions config_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -35,7 +35,7 @@ func TestHotCacheConfig(t *testing.T) {
cacheAlgo: LRU, cacheCapacity: 42, missingSharedCache: false, missingCacheAlgo: "", missingCacheCapacity: 0,
ttl: 0, stale: 0, jitterLambda: 0, jitterUpperBound: 0, shards: 0, shardingFn: nil,
lockingDisabled: false, janitorEnabled: false, prometheusMetricsEnabled: false, cacheName: "",
warmUpFn: nil, loaderFns: nil, revalidationLoaderFns: nil, revalidationErrorPolicy: DropOnError,
preloadFn: nil, loaderFns: nil, revalidationLoaderFns: nil, revalidationErrorPolicy: DropOnError,
onEviction: nil, copyOnRead: nil, copyOnWrite: nil,
}, opts)

Expand All @@ -44,7 +44,7 @@ func TestHotCacheConfig(t *testing.T) {
cacheAlgo: LRU, cacheCapacity: 42, missingSharedCache: true, missingCacheAlgo: "", missingCacheCapacity: 0,
ttl: 0, stale: 0, jitterLambda: 0, jitterUpperBound: 0, shards: 0, shardingFn: nil,
lockingDisabled: false, janitorEnabled: false, prometheusMetricsEnabled: false, cacheName: "",
warmUpFn: nil, loaderFns: nil, revalidationLoaderFns: nil, revalidationErrorPolicy: DropOnError,
preloadFn: nil, loaderFns: nil, revalidationLoaderFns: nil, revalidationErrorPolicy: DropOnError,
onEviction: nil, copyOnRead: nil, copyOnWrite: nil,
}, opts)

Expand All @@ -53,7 +53,7 @@ func TestHotCacheConfig(t *testing.T) {
cacheAlgo: LRU, cacheCapacity: 42, missingSharedCache: false, missingCacheAlgo: LFU, missingCacheCapacity: 21,
ttl: 0, stale: 0, jitterLambda: 0, jitterUpperBound: 0, shards: 0, shardingFn: nil,
lockingDisabled: false, janitorEnabled: false, prometheusMetricsEnabled: false, cacheName: "",
warmUpFn: nil, loaderFns: nil, revalidationLoaderFns: nil, revalidationErrorPolicy: DropOnError,
preloadFn: nil, loaderFns: nil, revalidationLoaderFns: nil, revalidationErrorPolicy: DropOnError,
onEviction: nil, copyOnRead: nil, copyOnWrite: nil,
}, opts)

Expand All @@ -65,7 +65,7 @@ func TestHotCacheConfig(t *testing.T) {
cacheAlgo: LRU, cacheCapacity: 42, missingSharedCache: false, missingCacheAlgo: LFU, missingCacheCapacity: 21,
ttl: 42 * time.Second, stale: 0, jitterLambda: 0, jitterUpperBound: 0, shards: 0, shardingFn: nil,
lockingDisabled: false, janitorEnabled: false, prometheusMetricsEnabled: false, cacheName: "",
warmUpFn: nil, loaderFns: nil, revalidationLoaderFns: nil, revalidationErrorPolicy: DropOnError,
preloadFn: nil, loaderFns: nil, revalidationLoaderFns: nil, revalidationErrorPolicy: DropOnError,
onEviction: nil, copyOnRead: nil, copyOnWrite: nil,
}, opts)

Expand All @@ -84,7 +84,7 @@ func TestHotCacheConfig(t *testing.T) {
cacheAlgo: LRU, cacheCapacity: 42, missingSharedCache: false, missingCacheAlgo: LFU, missingCacheCapacity: 21,
ttl: 42 * time.Second, stale: 0, jitterLambda: 2, jitterUpperBound: time.Second, shards: 0, shardingFn: nil,
lockingDisabled: false, janitorEnabled: false, prometheusMetricsEnabled: false, cacheName: "",
warmUpFn: nil, loaderFns: nil, revalidationLoaderFns: nil, revalidationErrorPolicy: DropOnError,
preloadFn: nil, loaderFns: nil, revalidationLoaderFns: nil, revalidationErrorPolicy: DropOnError,
onEviction: nil, copyOnRead: nil, copyOnWrite: nil,
}, opts)

Expand All @@ -96,7 +96,7 @@ func TestHotCacheConfig(t *testing.T) {
cacheAlgo: LRU, cacheCapacity: 42, missingSharedCache: false, missingCacheAlgo: LFU, missingCacheCapacity: 21,
ttl: 42 * time.Second, stale: 0, jitterLambda: 2, jitterUpperBound: time.Second, shards: 0, shardingFn: nil,
lockingDisabled: true, janitorEnabled: false, prometheusMetricsEnabled: false, cacheName: "",
warmUpFn: nil, loaderFns: nil, revalidationLoaderFns: nil, revalidationErrorPolicy: DropOnError,
preloadFn: nil, loaderFns: nil, revalidationLoaderFns: nil, revalidationErrorPolicy: DropOnError,
onEviction: nil, copyOnRead: nil, copyOnWrite: nil,
}, opts)

Expand All @@ -105,7 +105,7 @@ func TestHotCacheConfig(t *testing.T) {
cacheAlgo: LRU, cacheCapacity: 42, missingSharedCache: false, missingCacheAlgo: LFU, missingCacheCapacity: 21,
ttl: 42 * time.Second, stale: 0, jitterLambda: 2, jitterUpperBound: time.Second, shards: 0, shardingFn: nil,
lockingDisabled: true, janitorEnabled: true, prometheusMetricsEnabled: false, cacheName: "",
warmUpFn: nil, loaderFns: nil, revalidationLoaderFns: nil, revalidationErrorPolicy: DropOnError,
preloadFn: nil, loaderFns: nil, revalidationLoaderFns: nil, revalidationErrorPolicy: DropOnError,
onEviction: nil, copyOnRead: nil, copyOnWrite: nil,
}, opts)

Expand Down Expand Up @@ -159,28 +159,64 @@ func TestWithWarmUpWithTimeout(t *testing.T) {
is := assert.New(t)
t.Parallel()

// Minimal test for backward compatibility - deprecated API
opts := NewHotCache[string, int](LRU, 42)

// Test successful warmup
warmUpFn := func() (map[string]int, []string, error) {
return map[string]int{"key1": 1, "key2": 2}, []string{"missing1"}, nil
preloadFn := func() (map[string]int, []string, error) {
return map[string]int{"key1": 1}, []string{}, nil
}

opts = opts.WithWarmUpWithTimeout(100*time.Millisecond, warmUpFn)
is.NotNil(opts.warmUpFn)
opts = opts.WithWarmUpWithTimeout(100*time.Millisecond, preloadFn)
is.NotNil(opts.preloadFn)
}

// Test timeout
slowWarmUpFn := func() (map[string]int, []string, error) {
time.Sleep(200 * time.Millisecond)
return map[string]int{"key1": 1}, []string{}, nil
func TestWithPreload(t *testing.T) {
is := assert.New(t)
t.Parallel()

counter := 0
preloadFn := func() (map[string]int, []string, error) {
counter++
if counter > 5 {
time.Sleep(200 * time.Millisecond)
}
return map[string]int{"key1": counter}, []string{}, nil
}

opts = opts.WithWarmUpWithTimeout(50*time.Millisecond, slowWarmUpFn)
result, missing, err := opts.warmUpFn()
is.Nil(result)
is.Nil(missing)
is.Error(err)
is.Contains(err.Error(), "WarmUp timeout")
cache := NewHotCache[string, int](LRU, 42).
WithTTL(500 * time.Millisecond).WithPreload(Preloader[string, int]{
Fn: preloadFn,
Timeout: 100 * time.Millisecond,
Period: 50 * time.Millisecond,
}).Build()

// Verify initial preload
v, ok, err := cache.Get("key1")
is.True(ok)
is.NoError(err)
is.Equal(1, v)

// Wait for periodic refresh
time.Sleep(200 * time.Millisecond)

// Verify cache was refreshed
v, ok, err = cache.Get("key1")
is.True(ok)
is.NoError(err)
is.Greater(v, 1)

// Stop periodic preload
cache.StopPeriodicPreload()
vAfterStop, ok, err := cache.Get("key1")
is.True(ok)
is.NoError(err)

time.Sleep(150 * time.Millisecond)

// Verify cache was NOT refreshed after stop
vFinal, ok, err := cache.Get("key1")
is.True(ok)
is.NoError(err)
is.Equal(vAfterStop, vFinal, "Cache should not be refreshed after StopPeriodicPreload")
}

func TestWithEvictionCallback(t *testing.T) {
Expand Down Expand Up @@ -272,23 +308,23 @@ func TestBuildWithJanitorAndLockingConflict(t *testing.T) {
})
}

func TestBuildWithWarmUp(t *testing.T) {
func TestBuildWithPreload(t *testing.T) {
is := assert.New(t)
t.Parallel()

warmUpFn := func() (map[string]int, []string, error) {
preloader := Preloader[string, int]{Fn: func() (map[string]int, []string, error) {
return map[string]int{"key1": 1, "key2": 2}, []string{"missing1"}, nil
}
}}

is.Panics(func() {
_ = NewHotCache[string, int](LRU, 42).
WithWarmUp(warmUpFn).
WithPreload(preloader).
Build()
})

cache := NewHotCache[string, int](LRU, 42).
WithMissingCache(LFU, 21).
WithWarmUp(warmUpFn).Build()
WithPreload(preloader).Build()
is.NotNil(cache)
}

Expand Down
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