Serverless Backend with AWS Lambda & API Gateway · 课时

错误处理、重试与死信队列

通过理解错误如何传播、不同调用类型的重试机制，以及死信队列如何捕获失败，构建稳健的 Lambda 函数。

错误处理、重试与死信队列 是 CoddyKit 上的免费 Serverless Backend with AWS Lambda & API Gateway 课时。这是第 4 节课，共 4 节。你可以在下方免费阅读本课时的完整内容 — 然后在浏览器中使用内置代码编辑器和全天候 AI 导师进行实践。这是 Serverless Backend with AWS Lambda & API Gateway 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 Serverless Backend with AWS Lambda & API Gateway 课程共包含 4 节课。

本课时的部分内容尚未翻译，以英文显示。

Errors in Serverless Functions

When a function throws or times out, the platform treats it as a failed invocation. How that failure is handled depends on how the function was invoked.

Synchronous: error returns to the caller
Asynchronous: platform retries automatically
Stream/poll: behavior depends on the source

Synchronous Error Handling

For synchronous calls (like an API request) the error is returned immediately to the caller. The caller, such as API Gateway, decides how to map it to an HTTP status.

Asynchronous Retries

For asynchronous invocations the platform automatically retries failed events a couple of times with delay before giving up. Your code must be safe to run more than once.

Idempotency

Because retries can re-run an event, functions should be idempotent: processing the same event twice produces the same result without duplicate side effects.

def handler(event, context):
    key = event["id"]
    if already_processed(key):
        return "skip"
    process(key)
    mark_processed(key)
    return "ok"

Try/Except in the Handler

Catch expected errors and respond gracefully; let truly unexpected errors bubble up so the platform can retry or record them.

def handler(event, context):
    try:
        return do_work(event)
    except ValidationError as e:
        return {"statusCode": 400, "body": str(e)}

Dead-Letter Queues

A dead-letter queue (DLQ) captures events that still fail after all retries, so they are not lost. You can inspect and reprocess them later.

Attach an SQS queue or SNS topic as the DLQ
Failed events land there with metadata

Configuring a DLQ

You point the function at a DLQ target. After exhausting retries, the platform delivers the failed event there instead of dropping it.

aws lambda update-function-configuration \
  --function-name worker \
  --dead-letter-config TargetArn=arn:aws:sqs:...:failed-events

Destinations: Success and Failure

Beyond DLQs, destinations route the result of async invocations on success or failure to another service, with richer context than a DLQ provides.

Handling Stream Failures

For stream sources (like a queue or stream), a failing batch can block progress. Configure batch bisection or a maximum retry age so a single poison message does not stall the whole stream.

Timeouts vs Errors

A timeout is a kind of failure: the function did not finish in time. Set timeouts realistically and instrument long operations so you can tell timeouts apart from thrown errors.

Observability for Failures

Log errors with context, emit metrics for failure counts, and alarm on DLQ depth. A growing DLQ is an early signal that something is systematically broken.

Quick Check

Test your error-handling understanding.

Recap

You learned robust Lambda error handling: how errors propagate per invocation type, why idempotency matters with retries, how to use try/except wisely, and how dead-letter queues and destinations capture failures so events are never silently lost.

常见问题解答

「错误处理、重试与死信队列」课时是免费的吗？

是的 — 「错误处理、重试与死信队列」的完整文本可在网页上免费阅读。要进行交互式练习（内置代码编辑器和全天候 AI 导师）并解锁 Serverless Backend with AWS Lambda & API Gateway 课程的其余内容，请升级到 CoddyKit PRO。 Serverless Backend with AWS Lambda & API Gateway 课程共包含 4 节课。

「错误处理、重试与死信队列」这节课中我会学到什么？

通过理解错误如何传播、不同调用类型的重试机制，以及死信队列如何捕获失败，构建稳健的 Lambda 函数。你通过在浏览器中直接运行的动手代码来练习 Serverless Backend with AWS Lambda & API Gateway，全天候 AI 导师会在你学习这节课的过程中回答你的问题。

学习 Serverless Backend with AWS Lambda & API Gateway 需要有经验吗？

无需任何先前经验。CoddyKit 上的 Serverless Backend with AWS Lambda & API Gateway 课程适合初学者到高级学习者，你可以从这里开始或从头开始，按照自己的节奏学习。这是第 4 节课，共 4 节。

「错误处理、重试与死信队列」课时需要多长时间？

大多数 CoddyKit 课程大约需要 5–10 分钟。每节课都很精短且互动，所以你能稳步进步，并在网页和应用中从离开的地方继续。

我能在这节 Serverless Backend with AWS Lambda & API Gateway 课中编写并运行代码吗？

能。每节 Serverless Backend with AWS Lambda & API Gateway 课都包含内置代码编辑器，你可以在浏览器中直接编写并运行真实代码，并获得即时 AI 反馈 — 无需本地设置。

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