cold start optimization

Author: devksingh4

cloudformation/iam.yml

@@ -143,6 +143,15 @@ Resources:
                 - lambda.amazonaws.com
 
       Policies:
+        - PolicyName: lambda-self-invoke
+          PolicyDocument:
+            Version: "2012-10-17"
+            Statement:
+              - Action:
+                  - lambda:invokeFunction
+                Effect: Allow
+                Resource:
+                  - Fn::Sub: "arn:aws:lambda:${AWS::Region}:${AWS::AccountId}:function:${LambdaFunctionName}"
         - PolicyName: lambda-generic
           PolicyDocument:
             Version: "2012-10-17"

cloudformation/main.yml

@@ -192,6 +192,16 @@ Resources:
             RestApiId: !Ref AppApiGateway
             Path: /{proxy+}
             Method: ANY
+        WarmingSchedule:
+          Type: Schedule
+          Properties:
+            Schedule: !If [
+              ShouldAttachVpc,
+              'rate(15 minutes)',
+              'rate(5 minutes)'
+              ]
+            Input: '{ "warmer":true,"concurrency":3 }'
+
 
   AppSqsLambdaFunction:
     Type: AWS::Serverless::Function

src/api/lambda.ts

@@ -1,12 +1,23 @@
 import "zod-openapi/extend";
 import awsLambdaFastify from "@fastify/aws-lambda";
 import init from "./index.js";
+import warmer from "lambda-warmer";
+import { type APIGatewayEvent, type Context } from "aws-lambda";
 
 const app = await init();
-const handler = awsLambdaFastify(app, {
+const realHandler = awsLambdaFastify(app, {
   decorateRequest: false,
   serializeLambdaArguments: true,
   callbackWaitsForEmptyEventLoop: false,
 });
+const handler = async (event: APIGatewayEvent, context: Context) => {
+  // if a warming event
+  if (await warmer(event, { correlationId: context.awsRequestId }, context)) {
+    return "warmed";
+  }
+  // else proceed with handler logic
+  return realHandler(event, context);
+};
+
 await app.ready(); // needs to be placed after awsLambdaFastify call because of the decoration: https://github.com/fastify/aws-lambda-fastify/blob/master/index.js#L9
 export { handler };

src/api/package.json

@@ -49,6 +49,7 @@
     "ioredis": "^5.6.1",
     "jsonwebtoken": "^9.0.2",
     "jwks-rsa": "^3.2.0",
+    "lambda-warmer": "^2.3.0",
     "moment": "^2.30.1",
     "moment-timezone": "^0.5.48",
     "node-cache": "^5.1.2",