Merge pull request #202 from sacloud/bill-api-cache

billing APIをキャッシュする

platform/bill.go

@@ -19,27 +19,42 @@ import (
 	"errors"
 	"fmt"
 	"sync"
+	"time"
 
 	"github.com/sacloud/iaas-api-go"
 	"github.com/sacloud/iaas-api-go/types"
 )
 
+var (
+	BillAPIUpdateHourJST   = 4
+	BillAPIUpdateMinuteJST = 30
+)
+
 // BillClient calls SakuraCloud bill API
 type BillClient interface {
 	Read(context.Context) (*iaas.Bill, error)
 }
 
 func getBillClient(caller iaas.APICaller) BillClient {
-	return &billClient{caller: caller}
+	return &billClient{
+		caller: caller,
+		cache:  newCache(30 * time.Minute),
+	}
 }
 
 type billClient struct {
 	caller    iaas.APICaller
 	accountID types.ID
 	once      sync.Once
+	cache     *cache
 }
 
 func (c *billClient) Read(ctx context.Context) (*iaas.Bill, error) {
+	ca := c.cache.get()
+	if ca != nil {
+		return ca.(*iaas.Bill), nil
+	}
+
 	var err error
 	c.once.Do(func() {
 		var auth *iaas.AuthStatus
@@ -74,5 +89,36 @@ func (c *billClient) Read(ctx context.Context) (*iaas.Bill, error) {
 			bill = b
 		}
 	}
+
+	n, err := nextCacheExpiresAt()
+	if err != nil {
+		return nil, err
+	}
+	err = c.cache.set(bill, n)
+	if err != nil {
+		return nil, err
+	}
+
 	return bill, nil
 }
+
+// キャッシュの有効期限を算出する
+//
+// Billing APIは1日1回 AM4:30 (JST) にデータが更新される。
+// このため、現在時刻がAM4:30 (JST) よりも早ければ当日のAM4:30 (JST)、
+// 現在時刻がAM4:30 (JST) よりも遅ければ翌日のAM4:30 (JST) を有効期限として扱う。
+func nextCacheExpiresAt() (time.Time, error) {
+	jst, err := time.LoadLocation("Asia/Tokyo")
+	if err != nil {
+		return time.Time{}, err
+	}
+
+	// 実行環境のタイムゾーンは不定のためJSTを基準にする
+	now := time.Now().In(jst)
+	expiresAt := time.Date(now.Year(), now.Month(), now.Day(), BillAPIUpdateHourJST, BillAPIUpdateMinuteJST, 0, 0, jst)
+	if now.Equal(expiresAt) || now.After(expiresAt) {
+		expiresAt = expiresAt.Add(24 * time.Hour)
+	}
+
+	return expiresAt, nil
+}

platform/cache.go

@@ -0,0 +1,50 @@
+package platform
+
+import (
+	"errors"
+	"sync"
+	"time"
+)
+
+type cache struct {
+	cleanupInterval time.Duration
+	expiresAt       time.Time
+	item            any
+	mu              sync.Mutex
+}
+
+func newCache(cleanupInterval time.Duration) *cache {
+	c := &cache{
+		cleanupInterval: cleanupInterval,
+	}
+
+	return c
+}
+
+func (c *cache) set(item any, expiresAt time.Time) error {
+	if item == nil {
+		return errors.New("item is not set")
+	}
+	if expiresAt.IsZero() {
+		return errors.New("expiresAt is not set")
+	}
+
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	c.item = item
+	c.expiresAt = expiresAt
+
+	return nil
+}
+
+func (c *cache) get() any {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	if time.Now().After(c.expiresAt) {
+		return nil
+	}
+
+	return c.item
+}

platform/cache_test.go

@@ -0,0 +1,69 @@
+package platform
+
+import (
+	"testing"
+	"time"
+)
+
+func TestNewCache(t *testing.T) {
+	cleanupInterval := 10 * time.Minute
+	cache := newCache(cleanupInterval)
+	if cache.cleanupInterval != cleanupInterval {
+		t.Errorf("expected cleanupInterval %v, got %v", cleanupInterval, cache.cleanupInterval)
+	}
+}
+
+func TestCache_Set(t *testing.T) {
+	cleanupInterval := 10 * time.Minute
+	cache := newCache(cleanupInterval)
+
+	item := "dummy_item"
+	expiresAt := time.Now().Add(1 * time.Hour)
+	err := cache.set(item, expiresAt)
+	if err != nil {
+		t.Error(err)
+	}
+	if cache.item != item {
+		t.Errorf("item %v, got %v", item, cache.item)
+	}
+	if cache.expiresAt != expiresAt {
+		t.Errorf("expiresAt %v, got %v", expiresAt, cache.expiresAt)
+	}
+}
+
+func TestCache_Get_ItemNotExpired(t *testing.T) {
+	cleanupInterval := 10 * time.Minute
+	cache := newCache(cleanupInterval)
+
+	item := "dummy_item"
+	expiresAt := time.Now().Add(1 * time.Hour)
+	err := cache.set(item, expiresAt)
+	if err != nil {
+		t.Error(err)
+	}
+
+	cachedItem := cache.get()
+	if cachedItem != item {
+		t.Errorf("cachedItem %v, got %v", item, cachedItem)
+	}
+}
+
+func TestCache_Get_ItemExpired(t *testing.T) {
+	cleanupInterval := 1 * time.Second
+	cache := newCache(cleanupInterval)
+
+	item := "dummy_item"
+	expiresAt := time.Now().Add(1 * time.Second)
+	err := cache.set(item, expiresAt)
+	if err != nil {
+		t.Error(err)
+	}
+
+	// キャッシュの期限切れと削除が行われるのを待つ
+	time.Sleep(2 * time.Second)
+
+	cachedItem := cache.get()
+	if cachedItem != nil {
+		t.Errorf("cached item not cleared, got %v", cachedItem)
+	}
+}