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package main
import (
"context"
"errors"
"log"
"time"
"github.com/viccon/sturdyc"
)
type API struct {
*sturdyc.Client[string]
count int
}
func NewAPI(c *sturdyc.Client[string]) *API {
return &API{c, 0}
}
func (a *API) Get(ctx context.Context, key string) (string, error) {
fetchFn := func(_ context.Context) (string, error) {
a.count++
log.Printf("Fetching value for key: %s\n", key)
if a.count > 3 {
return "value", nil
}
return "", sturdyc.ErrNotFound
}
return a.GetOrFetch(ctx, key, fetchFn)
}
func main() {
// ===========================================================
// ===================== Basic configuration =================
// ===========================================================
// Maximum number of entries in the sturdyc.
capacity := 10000
// Number of shards to use for the sturdyc.
numShards := 10
// Time-to-live for cache entries.
ttl := 2 * time.Hour
// Percentage of entries to evict when the cache is full. Setting this
// to 0 will make set a no-op if the cache has reached its capacity.
evictionPercentage := 10
// ===========================================================
// =================== Stampede protection ===================
// ===========================================================
// Set a minimum and maximum refresh delay for the sturdyc. This is
// used to spread out the refreshes for entries evenly over time.
minRefreshDelay := time.Millisecond * 10
maxRefreshDelay := time.Millisecond * 30
// Set a synchronous refresh delay for when we want a refresh to happen synchronously.
synchronousRefreshDelay := time.Second * 30
// The base for exponential backoff when retrying a refresh.
retryBaseDelay := time.Millisecond * 10
// Create a cache client with the specified configuration.
cacheClient := sturdyc.New[string](capacity, numShards, ttl, evictionPercentage,
sturdyc.WithEarlyRefreshes(minRefreshDelay, maxRefreshDelay, synchronousRefreshDelay, retryBaseDelay),
sturdyc.WithMissingRecordStorage(),
)
// Create a new API instance with the cache client.
api := NewAPI(cacheClient)
// We are going to retrieve the values every 10 milliseconds, however the
// logs will reveal that actual refreshes fluctuate randomly within a 10-30
// millisecond range. Even if this loop is executed across multiple
// goroutines, the API call frequency will maintain this variability,
// ensuring we avoid overloading the API with requests.
for i := 0; i < 100; i++ {
val, err := api.Get(context.Background(), "key")
if errors.Is(err, sturdyc.ErrMissingRecord) {
log.Println("Record does not exist.")
}
if err == nil {
log.Printf("Value: %s\n", val)
}
time.Sleep(minRefreshDelay)
}
}
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