Angular 14- Http Call with Retry

 

What is retry design pattern?

The retry pattern is a design pattern that can be used to handle errors and transient failures in a robust and fault-tolerant way. The basic idea behind the retry pattern is to automatically retry an operation in case of failure, with the hope that the operation will succeed on the next attempt.

The retry pattern typically involves the following steps:

• Attempt to perform the operation.
• If the operation fails, wait for a period of time before retrying.
• Retry the operation.
• If the operation still fails, increase the wait time before the next retry, or retry a fixed number of times before giving up.

The retry pattern can be implemented in various ways, such as using a loop with a fixed number of iterations or using a backoff algorithm that increases the wait time between retries exponentially.

The retry pattern can be useful in situations where the cause of the failure is transient, such as a temporary network outage or a temporary resource shortage. By retrying the operation, the system can automatically recover from these types of failures without the need for human intervention.

However, it's important to use the retry pattern carefully and with consideration to the specific use case. If a failure is likely to be permanent and not recoverable, retrying the operation will not be useful. Additionally, retrying too many times can cause additional load on the system and can also lead to an infinite loop

Here is an example of how you can retry an HTTP call in Angular 14 using the retryWhen operator from the rxjs library:

import { HttpClient } from '@angular/common/http';

import { retryWhen, delay, take } from 'rxjs/operators';

export class MyService {

  constructor(private http: HttpClient) {}

  getData() {

    return this.http.get('https://my-api.com/data').pipe(

      retryWhen(errors =>

        errors.pipe(

          delay(1000), // wait for 1 second before retrying

          take(5), // retry at most 5 times

          // if the error still persists after 5 retries, throw the error

          finalize(() => console.log("Retried 5 times, throwing error"))

        )

      )

    );

  }

}

In this example, the getData method makes a GET request to the specified URL and returns the response. The retryWhen operator is used to retry the request in case of an error. The errors observable passed to retryWhen emits an error event for each failed attempt. The errors observable is piped to delay operator which will wait for 1 second before retrying the request, take operator will retry the request at most 5 times, and finalize operator will log a message after retries are completed.

It is essential to set a maximum number of retries and a delay between retries to prevent an infinite loop of requests. In this example, we are retrying the request at most 5 times and waiting for 1 second between each retry. This helps avoid overwhelming the server with too many requests in a short time. Additionally, it is a good practice to log in or notify the user that the service is retrying the request, so they are aware of what is happening.

It is also important to note that retries should be used judiciously, as they may not always be the best solution for handling errors. In some cases, it may be better to handle the error and display a message to the user or take another action.