aws-cloud-patterns

AWS Cloud Patterns

Lambda 函数模式

import { APIGatewayProxyHandlerV2 } from "aws-lambda";
import { DynamoDBClient } from "@aws-sdk/client-dynamodb";
import { DynamoDBDocumentClient, GetCommand } from "@aws-sdk/lib-dynamodb";

const client = DynamoDBDocumentClient.from(new DynamoDBClient({}));

export const handler: APIGatewayProxyHandlerV2 = async (event) => {
  const id = event.pathParameters?.id;
  if (!id) {
    return { statusCode: 400, body: JSON.stringify({ error: "Missing id" }) };
  }

  const result = await client.send(
    new GetCommand({ TableName: process.env.TABLE_NAME!, Key: { pk: id } })
  );

  if (!result.Item) {
    return { statusCode: 404, body: JSON.stringify({ error: "Not found" }) };
  }

  return {
    statusCode: 200,
    headers: { "Content-Type": "application/json" },
    body: JSON.stringify(result.Item),
  };
};

在处理程序外初始化 SDK 客户端，以便在多次调用之间复用连接。

DynamoDB 单表设计

interface OrderItem {
  pk: string;          // USER#<userId>
  sk: string;          // ORDER#<orderId>
  gsi1pk: string;      // ORDER#<orderId>
  gsi1sk: string;      // ITEM#<itemId>
  entityType: string;  // "Order" | "OrderItem"
  data: Record<string, any>;
  ttl?: number;
}

const params = {
  TableName: "AppTable",
  KeyConditionExpression: "pk = :pk AND begins_with(sk, :prefix)",
  ExpressionAttributeValues: {
    ":pk": `USER#${userId}`,
    ":prefix": "ORDER#",
  },
};

先设计访问模式，再对键进行建模。使用 GSI 支持其他查询模式。

CDK 基础设施

import * as cdk from "aws-cdk-lib";
import { Construct } from "constructs";
import * as lambda from "aws-cdk-lib/aws-lambda-nodejs";
import * as dynamodb from "aws-cdk-lib/aws-dynamodb";
import * as apigateway from "aws-cdk-lib/aws-apigatewayv2";

export class ApiStack extends cdk.Stack {
  constructor(scope: Construct, id: string, props?: cdk.StackProps) {
    super(scope, id, props);

    const table = new dynamodb.Table(this, "AppTable", {
      partitionKey: { name: "pk", type: dynamodb.AttributeType.STRING },
      sortKey: { name: "sk", type: dynamodb.AttributeType.STRING },
      billingMode: dynamodb.BillingMode.PAY_PER_REQUEST,
      pointInTimeRecovery: true,
      removalPolicy: cdk.RemovalPolicy.RETAIN,
    });

    const fn = new lambda.NodejsFunction(this, "ApiHandler", {
      entry: "src/handler.ts",
      runtime: cdk.aws_lambda.Runtime.NODEJS_22_X,
      architecture: cdk.aws_lambda.Architecture.ARM_64,
      memorySize: 256,
      timeout: cdk.Duration.seconds(10),
      environment: { TABLE_NAME: table.tableName },
    });

    table.grantReadWriteData(fn);
  }
}

S3 事件处理

import { S3Event } from "aws-lambda";
import { S3Client, GetObjectCommand } from "@aws-sdk/client-s3";

const s3 = new S3Client({});

export async function handler(event: S3Event) {
  for (const record of event.Records) {
    const bucket = record.s3.bucket.name;
    const key = decodeURIComponent(record.s3.object.key.replace(/\+/g, " "));

    const obj = await s3.send(new GetObjectCommand({ Bucket: bucket, Key: key }));
    const body = await obj.Body?.transformToString();

    await processFile(key, body);
  }
}

反模式

• 硬编码 AWS 凭证，而不是使用 IAM 角色
• 未恰当设置 Lambda 超时和内存
• 在 DynamoDB 上使用相当于 SELECT * 的扫描，而不是使用带键条件的查询
• 为每个 CRUD 操作创建一个 Lambda，而不是按领域分组
• 未为错误率和限流设置 CloudWatch 警报
• 未在 DynamoDB 表上启用时间点恢复

检查清单

• 在 Lambda 处理程序外初始化 SDK 客户端
• IAM 角色遵循最小权限原则
• 在设计表架构前设计好 DynamoDB 访问模式
• Lambda 使用 ARM64 架构以节省成本
• S3 存储桶启用版本控制和生命周期策略
• 为 Lambda 错误、持续时间和限流设置 CloudWatch 警报
• 将基础设施定义为代码（CDK 或 Terraform）
• 将密钥存储在 Systems Manager Parameter Store 或 Secrets Manager 中