CDN-like, middleware memory cache for Go applications with integrated shielding and Go 1.18 Generics.
package main
import (
"context"
"fmt"
"time"
"github.com/AlexSSD7/cache"
)
type Person struct {
Name string
Age uint32
}
func fetchPerson(name string) (*Person, error) {
// Heavy task here, like a DB call.
// Shielding makes the fetch functions
// mutually exclusive, to prevent
// unncecessary duplicate calls
// if there is no cache in memory.
// For the purpose of this example though,
// we will just return sample objects.
switch name {
case "John":
return &Person{Name: "John", Age: 27}, nil
case "Steve":
return &Person{Name: "Steve", Age: 32}, nil
default:
return nil, fmt.Errorf("unknown person with name '%v'", name)
}
}
func main() {
// Create a new ShieldedCache instance with 5-second GC interval.
cache := cache.NewShieldedCache[*Person](time.Second * 5)
cacheCtx, cacheCtxCancel := context.WithCancel(context.Background())
defer cacheCtxCancel()
// Worker is a separate goroutine running in background.
// It is responsible for evicting old, expired objects.
cache.StartWorker(cacheCtx)
// If there is "person_john" object in cache, return it. Otherwise, execute fetchPerson("John").
ret, hit, err := cache.Fetch("person_john", time.Minute, func() (*Person, error) {
return fetchPerson("John")
})
fmt.Printf("result: %+v, hit: %v, err: %v\n", ret.Data, hit, err)
// result: &{Name:John Age:27}, hit: false, err: <nil>
ret, hit, err = cache.Fetch("person_john", time.Minute, func() (*Person, error) {
return fetchPerson("John")
})
fmt.Printf("result: %+v, hit: %v, err: %v\n", ret.Data, hit, err)
// result: &{Name:John Age:27}, hit: true, err: <nil>
ret, hit, err = cache.Fetch("person_steve", time.Minute, func() (*Person, error) {
return fetchPerson("Steve")
})
fmt.Printf("result: %+v, hit: %v, err: %v\n", ret.Data, hit, err)
// result: &{Name:Steve Age:32}, hit: false, err: <nil>
ret, hit, err = cache.Fetch("person_alice", time.Minute, func() (*Person, error) {
return fetchPerson("Alice")
})
fmt.Printf("result: %+v, hit: %v, err: %v\n", ret, hit, err)
// result: <nil>, hit: false, err: unknown person with name 'Alice'
}MIT