NgxHttpRetryService

An Angular service that provides HTTP methods (GET, POST, PUT, DELETE) with built-in retry logic using RxJS's retry operator.

Table of Contents

• Installation
• Usage
  • Importing the Service
  • Available Methods
    • get
    • post
    • put
    • delete
  • Customizing Retries
• Retry Strategy
  • Non-Retryable Errors
  • Exponential Backoff
  • Custom Retry Conditions
• Error Handling
• Extending the Service
• FAQs
• Contributing
• License
• Author
• Changelog

Installation

Install the package via npm:

npm install ngx-http-retry

Usage

Importing the Service

Import NgxHttpRetryService into your Angular component or service:

import { NgxHttpRetryService } from 'ngx-http-retry';

@Component({
  // ...
})
export class YourComponent {
  constructor(private httpRetryService: NgxHttpRetryService) {}
}

Available Methods

The service provides the following methods, which mirror Angular's HttpClient methods but include retry logic:

• get<T>(url: string, options?: any, retries?: number, delayMs?: number): Observable<T>
• post<T>(url: string, body: any, options?: any, retries?: number, delayMs?: number): Observable<T>
• put<T>(url: string, body: any, options?: any, retries?: number, delayMs?: number): Observable<T>
• delete<T>(url: string, options?: any, retries?: number, delayMs?: number): Observable<T>

get

Performs a GET request with retry logic.

Parameters:

• url: string - The endpoint URL.
• options?: any - Optional HTTP options.
• retries?: number - Number of retry attempts (default: 3).
• delayMs?: number - Delay between retries in milliseconds (default: 1000).

Returns:

• Observable<T> - An observable of the response.

Example:

this.httpRetryService.get<User[]>('https://api.example.com/users')
  .subscribe(
    users => console.log(users),
    error => console.error('Request failed', error)
  );

post

Performs a POST request with retry logic.

Parameters:

• url: string - The endpoint URL.
• body: any - The payload to send.
• options?: any - Optional HTTP options.
• retries?: number - Number of retry attempts (default: 3).
• delayMs?: number - Delay between retries in milliseconds (default: 1000).

Returns:

• Observable<T> - An observable of the response.

Example:

const payload = { name: 'John Doe', email: 'john@example.com' };
this.httpRetryService.post<User>('https://api.example.com/users', payload)
  .subscribe(
    user => console.log('User created:', user),
    error => console.error('Request failed', error)
  );

put

Performs a PUT request with retry logic.

Parameters:

• url: string - The endpoint URL.
• body: any - The payload to update.
• options?: any - Optional HTTP options.
• retries?: number - Number of retry attempts (default: 3).
• delayMs?: number - Delay between retries in milliseconds (default: 1000).

Returns:

• Observable<T> - An observable of the response.

Example:

const updatedData = { name: 'Jane Doe' };
this.httpRetryService.put<User>('https://api.example.com/users/1', updatedData)
  .subscribe(
    user => console.log('User updated:', user),
    error => console.error('Request failed', error)
  );

delete

Performs a DELETE request with retry logic.

Parameters:

• url: string - The endpoint URL.
• options?: any - Optional HTTP options.
• retries?: number - Number of retry attempts (default: 3).
• delayMs?: number - Delay between retries in milliseconds (default: 1000).

Returns:

• Observable<T> - An observable of the response.

Example:

this.httpRetryService.delete<void>('https://api.example.com/users/1')
  .subscribe(
    () => console.log('User deleted'),
    error => console.error('Request failed', error)
  );

Customizing Retries

Customize the number of retries and delay between retries:

this.httpRetryService.get<User[]>('https://api.example.com/users', {}, 5, 2000)
  .subscribe(
    users => console.log(users),
    error => console.error('Request failed after retries', error)
  );

• Retries: 5
• Delay: 2000 milliseconds

Retry Strategy

The retry logic uses RxJS's retry operator with a custom strategy.

private retryStrategy<T>(retries: number, delayMs: number) {
  return retry<T>({
    count: retries,
    delay: (error: HttpErrorResponse, retryCount: number) => {
      if (this.isNonRetryableError(error)) {
        throw error;
      } else {
        console.warn(`Retry attempt #${retryCount}`);
        return timer(delayMs);
      }
    },
  });
}

Non-Retryable Errors

By default, the following HTTP errors are not retried:

• Client-side errors (4xx), except for 408 Request Timeout.

private isNonRetryableError(error: HttpErrorResponse): boolean {
  return error.status >= 400 && error.status < 500 && error.status !== 408;
}

Exponential Backoff

To implement exponential backoff, modify the retryStrategy:

private retryStrategy<T>(retries: number, delayMs: number) {
  return retry<T>({
    count: retries,
    delay: (error: HttpErrorResponse, retryCount: number) => {
      if (this.isNonRetryableError(error)) {
        throw error;
      } else {
        const backoffDelay = delayMs * Math.pow(2, retryCount - 1);
        console.warn(`Retry attempt #${retryCount} after ${backoffDelay}ms`);
        return timer(backoffDelay);
      }
    },
  });
}

Custom Retry Conditions

Customize retry conditions based on specific error codes or responses:

private retryStrategy<T>(retries: number, delayMs: number) {
  return retry<T>({
    count: retries,
    delay: (error: HttpErrorResponse, retryCount: number) => {
      if (this.isNonRetryableError(error) || retryCount > retries) {
        throw error;
      } else if (error.status === 500) {
        // Immediate retry for server errors
        return timer(0);
      } else {
        return timer(delayMs);
      }
    },
  });
}

Error Handling

Handle errors where you consume the service:

this.httpRetryService.get<User[]>('https://api.example.com/users')
  .subscribe(
    users => {
      // Successful response
    },
    error => {
      // Error after all retries
      console.error('Request failed', error);
    }
  );

Extending the Service

For extensive customization, extend NgxHttpRetryService:

@Injectable({
  providedIn: 'root',
})
export class CustomHttpRetryService extends NgxHttpRetryService {
  protected isNonRetryableError(error: HttpErrorResponse): boolean {
    // Custom logic (e.g., don't retry on 404)
    return error.status === 404;
  }
}

Use CustomHttpRetryService in your components:

constructor(private httpRetryService: CustomHttpRetryService) {}

FAQs

Does this service support Angular Universal (Server-Side Rendering)?

Yes, it is compatible with Angular Universal.

How is this different from using HttpClient directly?

NgxHttpRetryService wraps HttpClient methods and adds configurable retry logic.

Can I use this service for file uploads or downloads?

Yes, any HTTP request supported by HttpClient can be used.

Does it support HTTP interceptors?

Yes, any interceptors configured with HttpClient are applied.

Contributing

Contributions are welcome! Please submit issues or pull requests on GitHub.

License

This project is licensed under the MIT License. See the LICENSE file for details.

Author

Umar Draz

Changelog

v1.0.0

• Initial release with GET, POST, PUT, DELETE methods and retry logic.