在Go语言中,有一个名为golang.org/x/sync/singleflight
的包,它提供了SingleFlight的实现,以确保多个调用只执行一次。。在处理多个组件或模块需要从后端获取数据的情况下,为了提高效率,我们也可以使用 SingleFlight 技巧,确保多个组件对相同接口的调用只发起一次请求,从而减少不必要的网络开销。本文将介绍如何在 Angular 应用中实现 SingleFlight,并为所有的 HTTP GET 请求添加该优化机制。Vue,React可以类似处理。
1. SingleFlightService 的创建
首先,我们需要创建一个 SingleFlightService
服务,该服务负责管理正在执行的请求。以下是 SingleFlightService
的基本实现:
typescript
// singleflight.service.ts
import { Injectable } from '@angular/core';
import { from, Observable } from 'rxjs';
import { shareReplay } from 'rxjs/operators';
@Injectable({
providedIn: 'root'
})
export class SingleFlightService {
private inFlightRequests: { [key: string]: Observable<any> } = {};
execute<T>(key: string, action: () => Observable<T>): Observable<T> {
console.log('execute key', key)
if (!this.inFlightRequests[key]) {
this.inFlightRequests[key] = from(action()).pipe(
shareReplay(1)
);
}
return this.inFlightRequests[key];
}
}
2. SingleFlightInterceptor 的创建
接下来,我们需要创建一个拦截器 SingleFlightInterceptor
,该拦截器负责拦截 HTTP GET 请求并利用 SingleFlightService
来实现单飞功能。以下是 SingleFlightInterceptor
的基本实现:
typescript
// singleflight.interceptor.ts
import { Injectable } from '@angular/core';
import { HttpInterceptor, HttpRequest, HttpHandler, HttpEvent } from '@angular/common/http';
import { Observable } from 'rxjs';
import { SingleFlightService } from './singleflight.service';
@Injectable()
export class SingleFlightInterceptor implements HttpInterceptor {
constructor(private singleFlightService: SingleFlightService) { }
intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
// Check if it's a GET request
if (req.method === 'GET') {
const key = req.url; // You can customize the key based on your requirements
return this.singleFlightService.execute(key, () => next.handle(req));
}
// For non-GET requests, proceed without modification
return next.handle(req);
}
}
3. 在模块中注册拦截器
最后,在你的应用程序模块中,将 SingleFlightInterceptor
添加到 HTTP_INTERCEPTORS
提供商列表,以便在整个应用程序中生效:
typescript
// app.module.ts
import { NgModule } from '@angular/core';
import { HttpClientModule, HTTP_INTERCEPTORS } from '@angular/common/http';
import { SingleFlightInterceptor } from './singleflight.interceptor';
@NgModule({
imports: [HttpClientModule],
providers: [
{
provide: HTTP_INTERCEPTORS,
useClass: SingleFlightInterceptor,
multi: true
}
]
})
export class YourAppModule { }
4.不想全局使用可以单独封装一个service
typescript
import { Injectable } from '@angular/core';
@Injectable({
providedIn: 'root'
})
export class SingleFlightService {
private inFlightRequests: { [key: string]: Promise<any> } = {};
execute<T>(key: string, action: () => Promise<T>): Promise<T> {
console.log('execute key', key)
if (!this.inFlightRequests[key]) {
this.inFlightRequests[key] = action().then(data => {
// Clear the in-flight flag once the promise is resolved
delete this.inFlightRequests[key];
return data;
}).catch(error => {
// Handle errors here if needed
console.error(`Error in single flight request for key ${key}:`, error);
// Clear the in-flight flag in case of an error
delete this.inFlightRequests[key];
throw error;
});
}
return this.inFlightRequests[key];
}
}
// 使用方式
this.singleFlightService.execute(someKey, ()=> somePromseReq());