How to implement failover and retry of requests in FastAPI

How to implement request failure recovery and retry in FastAPI

Introduction:
In developing web applications, we often need to communicate with other services. However, these services may experience failures, such as temporary network outages or response timeouts. To keep our applications reliable, we need to recover from failures and retry when necessary. In this article, we will learn how to implement failover and retry of requests in FastAPI.

FastAPI is a modern web framework based on Python that provides simple and efficient request processing and routing functions. It uses an asynchronous method internally to process requests, which makes it easier to implement failure recovery and retries.

Implementation ideas for fault recovery and retry:
Before implementing the fault recovery and retry functions, we first need to understand some basic concepts.

1. Circuit Breaker mode:
   The circuit breaker is a design pattern that can prevent the spread of faults. When a service fails, the circuit breaker temporarily closes requests to the service for a certain period of time and returns the requests directly. This avoids further load on the failed service and gives the service some time to recover. When no fault occurs within a certain period of time, the circuit breaker will automatically recover and forward the request to the service again.
2. Retry mechanism:
   The retry mechanism is to resend the same request when the request fails, usually adding some delay time. The retry mechanism can ensure the reliability of the request and resend the request after failure recovery.

Based on the above ideas, we can achieve request failure recovery and retry by using the circuit breaker mode and retry mechanism.

Implementation steps:
The following code example demonstrates how to implement failure recovery and retry of requests in FastAPI:

from fastapi import FastAPI
import requests

app = FastAPI()

@app.get("/retry")
def retry():
    url = "http://example.com/api"  # 要请求的URL
    max_retries = 3  # 最大重试次数
    retry_interval = 1  # 重试间隔时间（秒）

    retries = 0
    while retries <= max_retries:
        try:
            response = requests.get(url)
            return response.json()
        except requests.exceptions.RequestException as error:
            print(f"Request failed: {error}")
            retries += 1
            time.sleep(retry_interval)

    return {"message": "Max retries exceeded"}

@app.get("/circuit-breaker")
def circuit_breaker():
    url = "http://example.com/api"  # 要请求的URL
    breaker = Breaker(url, max_failures=3, reset_timeout=10)

    try:
        response = breaker.execute(requests.get)
        return response.json()
    except BreakerOpenError:
        return {"message": "Service temporarily unavailable"}

class Breaker:
    def __init__(self, url, max_failures, reset_timeout):
        self.url = url
        self.max_failures = max_failures
        self.reset_timeout = reset_timeout
        self.failures = 0
        self.last_failure = None

    def execute(self, func):
        if self.failures >= self.max_failures:
            if self.last_failure and time.time() - self.last_failure < self.reset_timeout:
                raise BreakerOpenError()
            else:
                self.reset()

        try:
            response = func(self.url)
            self.failures = 0
            return response
        except requests.exceptions.RequestException as error:
            print(f"Request failed: {error}")
            self.failures += 1
            self.last_failure = time.time()

    def reset(self):
        self.failures = 0
        self.last_failure = None

class BreakerOpenError(Exception):
    pass

In the above code, we use retry and circuit_breaker are two routing examples to implement request failure recovery and retry. retryThe routing example uses a while loop to retry. When the request fails, it will wait for a period of time and then resend the request. circuit_breakerThe routing example uses a custom Circuit Breaker class, which will throw a custom BreakerOpenError exception after reaching the maximum number of failures.

Conclusion:
In this article, we learned how to implement failure recovery and retry of requests in FastAPI. By using the circuit breaker pattern and the retry mechanism, we can improve the reliability of the application and recover from failures. At the same time, we also demonstrated how to implement failure recovery and retry functions in FastAPI through sample code. I hope this article is helpful to you, thank you for reading!

The above is the detailed content of How to implement failover and retry of requests in FastAPI. For more information, please follow other related articles on the PHP Chinese website!