我想使用 Go 从 SQS 向 AWS 发送请求。有在单一事件模式下执行此操作的示例,使用
sqs.SendMessageInput
SDK 中的 v2
,但我想改为批量发送。我创建了一个接口来从我的其余代码中抽象出实现细节,如下所示:
type UserRepository interface {
Save(context.Context, User) error
}
如您所见,该接口不是特定于 SQS 的,可以很容易地替换为例如一个 Postgres 实现。我真的很想保持界面尽可能干净。
使用 SQS 有一些我能想到的注意事项,可能还有一些我没有想到的。 需要发送一批:
n
次Save
请注意,不是发送到 SQS,这也应该以类似的方式写入控制台,这是我在示例中创建的。
这种设计可行吗?还是我的界面中总是必须有一个
Close
功能?
代码的问题是最后4个(nr_of_items % batch_size)不会被“保存”。
package main
import (
"context"
"fmt"
"os"
"os/signal"
"sync"
"time"
)
type LoggingBufferedUserRepository struct {
buffer []string
bufferSize int
bufferTimeout time.Duration
mutex sync.Mutex
closeChan chan struct{}
}
func NewLoggingBufferedUserRepository(
ctx context.Context, bufferSize int, bufferTimeout time.Duration,
) *LoggingBufferedUserRepository {
client := &LoggingBufferedUserRepository{
bufferSize: bufferSize,
bufferTimeout: bufferTimeout,
closeChan: make(chan struct{}),
}
go client.bufferMonitor(ctx)
return client
}
func (c *LoggingBufferedUserRepository) SendMessage(ctx context.Context, input string) {
c.mutex.Lock()
defer c.mutex.Unlock()
c.buffer = append(c.buffer, input)
if len(c.buffer) >= c.bufferSize {
go c.flush(ctx, c.buffer)
c.buffer = []string{}
}
return
}
func (c *LoggingBufferedUserRepository) flush(ctx context.Context, buffer []string) {
if len(buffer) == 0 {
return
}
// This is the actual batch 'save':
fmt.Printf("flushing buffer, size=%d, cid=%s, buffer=$%v\n", len(buffer), ctx.Value("cid"), buffer)
}
func (c *LoggingBufferedUserRepository) bufferMonitor(ctx context.Context) {
timeout := time.NewTimer(c.bufferTimeout)
for {
select {
case <-timeout.C:
c.flush(ctx, c.buffer)
c.buffer = []string{}
}
timeout.Reset(c.bufferTimeout)
}
}
func main() {
ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt, os.Kill)
defer stop()
g := NewLoggingBufferedUserRepository(ctx, 10, 1*time.Second)
wg := &sync.WaitGroup{}
for i := 0; i < 15; i++ {
wg.Add(1)
go func(i int) {
defer wg.Done()
fmt.Printf("sending message %d\n", i)
g.SendMessage(ctx, fmt.Sprintf("a%d", i))
}(i)
time.Sleep(100 * time.Millisecond)
}
wg.Wait()
fmt.Println("done")
}
有多种方法可以做到这一点。一般来说,基于超时刷新此类缓冲实现是不可取的,因为您无法控制如果事情失败会发生什么。
一种方法是进行显式批处理操作:
type UserRepository interface {
// Save single user
Save(context.Context, User) error
// Save batch
SaveBatch(context.Context) UserBatch
}
在哪里
type UserBatch interface {
Save(context.Context,User) error
Flush(context.Context) error
Close(context.Context) error
}
接口是否支持批量操作 需要关闭功能?UserRepository
是的,一种解决方案是在您的界面中使用不同的
Flush
函数,调用者可以使用该函数显式刷新任何剩余的缓冲项。你的界面:
type UserRepository interface {
Save(context.Context, User) error
Flush(context.Context) error
SaveAll(context.Context) error
}
根据您的喜好实施此
UserRepository
的一个示例,可能类似于playground:
// for SO testing, by JS
package main
import (
"context"
"fmt"
"sync"
"time"
)
type User struct {
ID int
Name string
}
type UserRepository interface {
Save(context.Context, User) error
Flush(context.Context) error
SaveAll(context.Context) error
}
type LoggingBufferedUserRepository struct {
buffer []string
bufferSize int
bufferTimeout time.Duration
mutex sync.Mutex
// we don't need close here now
}
// add the item to the buffer and flushes the buffer if it reaches the configured size
func (c *LoggingBufferedUserRepository) Save(ctx context.Context, user User) error {
// implement save functionality
fmt.Printf("Save called %v: %v\n", user.Name, user.ID)
return nil
}
// can - Flush function immediately flushes any buffered items
func (c *LoggingBufferedUserRepository) Flush(ctx context.Context) error {
// implement Flush functionality
fmt.Printf("Flush called\n")
return nil
}
// waits for any pending items to be saved before returning, and flushes any remaining buffered items if there are any
func (c *LoggingBufferedUserRepository) SaveAll(ctx context.Context) error {
// implement SaveAll functionality
fmt.Printf("SaveAll called\n")
return nil
}
func (c *LoggingBufferedUserRepository) flush(ctx context.Context) error {
if len(c.buffer) == 0 {
return nil
}
// This is your actual batch 'save':
fmt.Printf("flushing buffer, size=%d, cid=%s, buffer=$%v\n", len(c.buffer), ctx.Value("cid"), c.buffer)
c.buffer = []string{}
return nil
}
func main() {
repo := &LoggingBufferedUserRepository{
bufferSize: 5,
bufferTimeout: 1 * time.Second,
}
users := []User{
{ID: 1, Name: "Alice"},
{ID: 2, Name: "Bob"},
{ID: 3, Name: "Charlie"},
{ID: 4, Name: "Dave"},
{ID: 5, Name: "Eve"},
}
for _, user := range users {
if err := repo.Save(context.Background(), user); err != nil {
fmt.Printf("error saving user %v: %v\n", user, err)
}
}
fmt.Printf("Waiting for flushing... (5 seconds)\n")
time.Sleep(5 * time.Second)
// Save remaining items
if err := repo.SaveAll(context.Background()); err != nil {
fmt.Printf("error saving remaining items: %v\n", err)
}
// Flush remaining items
if err := repo.Flush(context.Background()); err != nil {
fmt.Printf("error flushing remaining items: %v\n", err)
}
}
这个输出应该是:
Save called Alice: 1
Save called Bob: 2
Save called Charlie: 3
Save called Dave: 4
Save called Eve: 5
Waiting for flushing... (5 seconds)
SaveAll called
Flush called
Program exited.