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模块3：故事API实现

Section titled “模块3：故事API实现”

StoryApi包含一个单独的APIgenerate_story，该API接收一个Game和用于上下文的Action列表来推进故事情节。我们将使用Python/FastAPI将此API实现为流式API，并演示如何对生成的代码进行调整以满足实际需求。

API实现

Section titled “API实现”

要创建API，首先需要安装两个额外的依赖项：

  • boto3用于调用Amazon Bedrock；
  • uvicorn与Lambda Web Adapter (LWA)配合使用来启动API；
  • copyfiles是npm依赖项，用于在更新bundle任务时支持跨平台文件复制。

运行以下命令安装这些依赖项：

Terminal window
pnpm nx run dungeon_adventure.story_api:add --args boto3 uvicorn
Terminal window
pnpm add -Dw copyfiles

现在替换packages/story_api/story_api目录中的以下文件内容：

import json


from boto3 import client
from fastapi.responses import PlainTextResponse, StreamingResponse
from pydantic import BaseModel


from .init import app, lambda_handler


handler = lambda_handler


bedrock = client('bedrock-runtime')


class Action(BaseModel):
    role: str
    content: str


class StoryRequest(BaseModel):
    genre: str
    playerName: str
    actions: list[Action]


async def bedrock_stream(request: StoryRequest):
    messages = [
        {"role": "user", "content": "Continue or create a new story..."}
    ]


    for action in request.actions:
        messages.append({"role": action.role, "content": action.content})


    response = bedrock.invoke_model_with_response_stream(
        modelId='anthropic.claude-3-sonnet-20240229-v1:0',
        body=json.dumps({
            "system":f"""
            You are running an AI text adventure game in the {request.genre} genre.
            Player: {request.playerName}. Return less than 200 characters of text.
            """,
            "messages": messages,
            "max_tokens": 1000,
            "temperature": 0.7,
            "anthropic_version": "bedrock-2023-05-31"
        })
    )


    stream = response.get('body')
    if stream:
        for event in stream:
            chunk = event.get('chunk')
            if chunk:
                message = json.loads(chunk.get("bytes").decode())
                if message['type'] == "content_block_delta":
                    yield message['delta']['text'] or ""
                elif message['type'] == "message_stop":
                    yield "\n"


@app.post("/story/generate",
          openapi_extra={'x-streaming': True},
          response_class=PlainTextResponse)
def generate_story(request: StoryRequest) -> str:
    return StreamingResponse(bedrock_stream(request), media_type="text/plain")

代码分析：

  • 使用x-streaming设置标记为流式API，在生成客户端SDK时保持类型安全的流式消费
  • API通过media_type="text/plain"和response_class=PlainTextResponse定义返回纯文本流

基础设施

Section titled “基础设施”

先前设置的基础设施假设所有API都通过API Gateway与Lambda函数集成。对于story_api，我们需要使用支持响应流式的Lambda函数URL来替代API Gateway。

更新CDK构造如下：

import { Duration, Stack, CfnOutput } from 'aws-cdk-lib';
import { IGrantable, Grant } from 'aws-cdk-lib/aws-iam';
import {
  Runtime,
  Code,
  Tracing,
  LayerVersion,
  FunctionUrlAuthType,
  InvokeMode,
  Function,
} from 'aws-cdk-lib/aws-lambda';
import { Construct } from 'constructs';
import url from 'url';
import { RuntimeConfig } from '../../core/runtime-config.js';


export class StoryApi extends Construct {
  public readonly handler: Function;


  constructor(scope: Construct, id: string) {
    super(scope, id);


    this.handler = new Function(this, 'Handler', {
      runtime: Runtime.PYTHON_3_12,
      handler: 'run.sh',
      code: Code.fromAsset(
        url.fileURLToPath(
          new URL(
            '../../../../../../dist/packages/story_api/bundle',
            import.meta.url,
          ),
        ),
      ),
      timeout: Duration.seconds(30),
      tracing: Tracing.ACTIVE,
      environment: {
        AWS_CONNECTION_REUSE_ENABLED: '1',
      },
    });


    const stack = Stack.of(this);
    this.handler.addLayers(
      LayerVersion.fromLayerVersionArn(
        this,
        'LWALayer',
        `arn:aws:lambda:${stack.region}:753240598075:layer:LambdaAdapterLayerX86:24`,
      ),
    );
    this.handler.addEnvironment('PORT', '8000');
    this.handler.addEnvironment('AWS_LWA_INVOKE_MODE', 'response_stream');
    this.handler.addEnvironment('AWS_LAMBDA_EXEC_WRAPPER', '/opt/bootstrap');
    const functionUrl = this.handler.addFunctionUrl({
      authType: FunctionUrlAuthType.AWS_IAM,
      invokeMode: InvokeMode.RESPONSE_STREAM,
      cors: {
        allowedOrigins: ['*'],
        allowedHeaders: [
          'authorization',
          'content-type',
          'x-amz-content-sha256',
          'x-amz-date',
          'x-amz-security-token',
        ],
      },
    });


    new CfnOutput(this, 'StoryApiUrl', { value: functionUrl.url });


    // Register the API URL in runtime configuration for client discovery
    RuntimeConfig.ensure(this).config.apis = {
      ...RuntimeConfig.ensure(this).config.apis!,
      StoryApi: functionUrl.url,
    };
  }


  public grantInvokeAccess(grantee: IGrantable) {
    Grant.addToPrincipal({
      grantee,
      actions: ['lambda:InvokeFunctionUrl'],
      resourceArns: [this.handler.functionArn],
      conditions: {
        StringEquals: {
          'lambda:FunctionUrlAuthType': 'AWS_IAM',
        },
      },
    });
  }
}

更新story_api以支持Lambda Web Adapter部署：

#!/bin/bash


PATH=$PATH:$LAMBDA_TASK_ROOT/bin \
    PYTHONPATH=$PYTHONPATH:/opt/python:$LAMBDA_RUNTIME_DIR \
    exec python -m uvicorn --port=$PORT story_api.main:app

部署与测试

Section titled “部署与测试”

首先构建代码库：

Terminal window
pnpm nx run-many --target build --all

运行以下命令部署应用：

Terminal window
pnpm nx run @dungeon-adventure/infra:deploy dungeon-adventure-infra-sandbox

部署过程约需2分钟。

点击查看同时部署所有堆栈的详细信息

部署完成后将看到类似输出（部分值已脱敏）：

Terminal window
dungeon-adventure-infra-sandbox
dungeon-adventure-infra-sandbox: deploying... [2/2]


 ✅  dungeon-adventure-infra-sandbox


✨  部署时间：354秒


输出：
dungeon-adventure-infra-sandbox.ElectroDbTableTableNameXXX = dungeon-adventure-infra-sandbox-ElectroDbTableXXX-YYY
dungeon-adventure-infra-sandbox.GameApiEndpointXXX = https://xxx.execute-api.region.amazonaws.com/prod/
dungeon-adventure-infra-sandbox.GameUIDistributionDomainNameXXX = xxx.cloudfront.net
dungeon-adventure-infra-sandbox.StoryApiStoryApiUrlXXX = https://xxx.lambda-url.ap-southeast-2.on.aws/
dungeon-adventure-infra-sandbox.UserIdentityUserIdentityIdentityPoolIdXXX = region:xxx
dungeon-adventure-infra-sandbox.UserIdentityUserIdentityUserPoolIdXXX = region_xxx

可通过以下方式测试API：

  • 启动FastAPI本地实例并使用curl调用
  • 直接调用已部署API（使用Sigv4签名curl）

运行以下命令启动FastAPI服务：

Terminal window
pnpm nx run dungeon_adventure.story_api:serve

服务启动后执行：

Terminal window
curl -N -X POST http://127.0.0.1:8000/story/generate \
  -d '{"genre":"superhero", "actions":[], "playerName":"UnnamedHero"}' \
  -H "Content-Type: application/json"

成功执行后将看到流式响应：

UnnamedHero迎风而立，披风猎猎作响....

恭喜！您已成功使用FastAPI构建并部署了首个流式API！🎉🎉🎉