serverless-aws-lambda


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> AWS Lambda dev tool for Serverless. Allows Express synthax in handlers. Supports packaging, local invoking and offline Application Load Balancer and API Gateway lambda server mocking.

- Plug & Play (easy to install, configure and use)
- Highly customizable
- Functions are bundled by esbuild
- Offline server uses NodeJS http module
- Packaging is made by node-archiver

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- NodeJS
- Python
- Ruby

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- Node v18.20.4+
- Serverless 2.0.0+ < 4.0

---

Table of Contents

- Installation
- Quick start
- Manual installation
- Usage
- Invoke
- Lifecycle
- Events
- AWS Test button
- Function URL
- Serverless Invoke local
- AWS SDK Lambda Client
- Stream Response
- Environment variables
- Package
- assets
- preserveDir
- files
- Deploy

- Advanced configuration
- Plugins
- Benchmarks

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#### Quick start

``bash
npx degit github:inqnuam/serverless-aws-lambda/templates/simple my-project
cd my-project && yarn install
yarn start
`

#### Manual installation

Usual node module installation...

`bash
yarn add -D serverless-aws-lambda


or


npm install -D serverless-aws-lambda
`

Then add the plugin to your serverless plugins list

`yaml
service: myapp

frameworkVersion: "3"
configValidationMode: error

plugins:
- serverless-aws-lambda
`

---

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Start the local server

`bash
SLS_DEBUG="*" sls aws-lambda -s dev
`

During development the env variable SLS_DEBUG="*" is strongly recommanded as it will print a bunch of useful information.
It is also possible to set server port from the CLI with --port or -p.

This will overwrite serverless.yml custom > serverless-aws-lambda > port value if it is set.
For more options see advanced configuration.

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#### Lambda execution lifecycles.

Succefull execution:
!lambda success
Failed execution:
!lambda error

#### Events

Offline server supports Application Load Balancer, API Gateway and Function URL endpoints out of box.
See plugins for more triggers (SNS, SQS, etc.).
Appropriate event object is sent to the handler based on your lambda declaration.

`yaml
functions:
myAwsomeLambda:
handler: src/handlers/awsomeLambda.default
events:
- alb:
listenerArn: arn:aws:elasticloadbalancing:eu-west-3:170838072631:listener/app/myAlb/bf88e6ec8f3d91df/e653b73728d04626
priority: 939
conditions:
path: "/paradise"
method: GET
`

All available local endpoints will be printed to the console when SLS_DEBUG="*" is set.

myAwsomeLambda is available at http://localhost:PORT/paradise

However if your declare both alb and http or httpApi inside a single lambda events with the same path you have to specify desired server by setting alb or apg inside your request's:

- header with X-Mock-Type.
- or in query string with x_mock_type.

Please note that invoking a lambda from sls CLI (sls invoke local -f myFunction) will not trigger the offline server. But will still make your handler ready to be invoked.

#### AWS Console Test button

To invoke your Lambda like with AWS Console's Test button, prefix your Lambda name by @invoke/.
Example:

`
http://localhost:3000/@invoke/myAwsomeLambda
`

#### Function URL

Function URL is available with @url/ prefix. (must be enabled inside lambda declaration).
Example:

`yaml
functions:
myAwsomeLambda:
handler: src/handlers/awsomeLambda.default
url: true
`

`
http://localhost:3000/@url/myAwsomeLambda
`

#### Serverless Invoke local

Works out of box.
see options
Example:

serverless invoke local -f myAwsomeLambda

#### AWS SDK

Invoking with aws-sdk Lambda Client requires to set client endpoint to local server host.

Example:

`js
import { LambdaClient, InvokeCommand } from "@aws-sdk/client-lambda";

const client = new LambdaClient({ region: "us-east-1", endpoint: "http://localhost:3000" });
const DryRun = "DryRun";
const Event = "Event";
const RequestResponse = "RequestResponse";

const cmd = new InvokeCommand({
FunctionName: "myAwsomeLambda",
InvocationType: RequestResponse,
Payload: Buffer.from(JSON.stringify({ foo: "bar" })),
});

client
.send(cmd)
.then((data) => {
data.Payload = new TextDecoder("utf-8").decode(data.Payload);
console.log(data);
})
.catch((error) => {
// 🥲
console.log("error", error);
});
`

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Stream responses are supported out of box through Function URL invoke or AWS SDK invoke.
See example:

`yaml
functions:
myAwsomeLambda:
handler: src/handlers/awsomeLambda.default
url: # required only for Function URL invoke
invokeMode: RESPONSE_STREAM
`

`ts
// awsomeLambda.ts
import stream from "stream";
import { promisify } from "util";
const pipeline = promisify(stream.pipeline);
import { createReadStream } from "fs";

export const handler = awslambda.streamifyResponse(async (event, responseStream, context) => {
responseStream.setContentType("image/png");
// https://svs.gsfc.nasa.gov/vis/a030000/a030800/a030877/frames/5760x3240_16x9_01p/BlackMarble_2016_928m_europe_labeled.png
const streamImage = createReadStream("BlackMarble_2016_928m_europe_labeled.png");

await pipeline(streamImage, responseStream);
});
`

Example with AWS SDK:

`ts
import { LambdaClient, InvokeWithResponseStreamCommand } from "@aws-sdk/client-lambda";

const client = new LambdaClient({
region: "eu-west-3",
endpoint: "http://localhost:3000",
});

const cmd = new InvokeWithResponseStreamCommand({
FunctionName: "myAwsomeLambda",
InvocationType: "RequestResponse",
Payload: Buffer.from(JSON.stringify({ hello: "world" })),
ClientContext: Buffer.from(JSON.stringify({ anything: "some value" })).toString("base64"),
});

const data = await client.send(cmd);

for await (const x of data.EventStream) {
if (x.PayloadChunk) {
console.log(x.PayloadChunk.Payload);
}
}
`

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Lambdas are executed in worker threads. \*Only variables declared in your serverless.yml are injected into process.env.

\*In local mode following env variables are set for sls invoke, serverless-offline and AWS SAM compatibility.

- IS_LOCAL
- IS_OFFLINE
- AWS_SAM_LOCAL

If NODE_ENV is present it will be injected in both local mode, while deploying also during bundle process for optimized output.

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serverless-aws-lambda bundles every (nodejs) handler separetly (with esbuild) and creates the artifact zip archive.
Archive will include bundeled handler and sourcemap (if enabled in esbuild).

#### - assets

By default bundle produced assets (css, png, svg etc.) are excluded.
To include all assets set assets to true.
For all functions set it at top-level package:

`yaml
package:
individually: true
assets: true # default false

functions:
myAwsomeLambda:
description: inherits assets from top-level package
handler: src/handlers/awsomeLambda.default
`

or by function:

`yaml
functions:
myAwsomeLambda:
package:
assets: false
description: don't includes assets
handler: src/handlers/awsomeLambda.default
`

include assets by file extension:

`yaml
functions:
myAwsomeLambda:
package:
assets: .css
description: include only css files
handler: src/handlers/awsomeLambda.default
`

`yaml
functions:
myAwsomeLambda:
package:
assets:
- .css
- .svg
description: include only css and svg files
handler: src/handlers/awsomeLambda.default
`

#### - preserveDir :

To preserve your project directories structure inside the archive set preserveDir globally or at function level.

`yaml
package:
individually: true
preserveDir: true # default true

functions:
myAwsomeLambda:
description: directories preserved
handler: src/handlers/awsomeLambda.default

dummyLambda:
package:
preserveDir: false
description: directories NOT preserved
handler: src/handlers/dummyLambda.default
`

#### - files

include additional files or directories into the package.

`yaml
functions:
myAwsomeLambda:
handler: src/handlers/awsomeLambda.default
package:
files:
- ./resources/some/file.png
- ./resources/anotherFile.pdf
- ./images
`

By default files are inherited from top level package's files.
This can be disabled with inheritFiles at function level.

`yaml
functions:
myAwsomeLambda:
handler: src/handlers/awsomeLambda.default
package:
inheritFiles: false
files:
- ./resources/some/file.png
- ./node_modules/my-module
`

files may be added to the archive with custom path:

`yaml
functions:
myAwsomeLambda:
handler: src/handlers/awsomeLambda.default
package:
files:
- { at: "./resources/some/file.png", as: "./documents/important.png" }
`

Adding files with a filter:

`yaml
functions:
myAwsomeLambda:
handler: src/handlers/awsomeLambda.default
package:
files:
- { pattern: "./resources/some/*.png" }
`

If you need to preserve pattern's directories structure inside the archive but search for files in another directory set dir value.
This will search for all .png files inside ./resources/images but only images directory will be created inside the archive.

`yaml
functions:
myAwsomeLambda:
handler: src/handlers/awsomeLambda.default
package:
files:
- { pattern: "images/*.png", dir: "./resources" }
`

Adding inline files:

`yaml
functions:
myAwsomeLambda:
handler: src/handlers/awsomeLambda.default
package:
files:
- { text: "Hello world", dir: "./documents/hello.txt" }
`

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Adding the param online: false will omit the deployement of your Lambda.

`yaml
functions:
myAwsomeLambda:
handler: src/handlers/awsomeLambda.default
online: false
`

To deploy a lambda by stage(s) set online's value to target stage(s)

`yaml
functions:
lambdaOnlyInDev:
handler: src/handlers/awsomeLambda.default
online: dev
`

`yaml
functions:
lambdaOnlyInDevAndTest:
handler: src/handlers/awsomeLambda.default
online:
- dev
- test
`

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- virtualEnvs
a key-value object which will only be available inside defineConfig.
by default virtualEnvs are inherited from custom > virtualEnvs if exists.

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To have more control over the plugin you can passe a config file via configPath param in plugin options:

`yaml
custom:
serverless-aws-lambda:
configPath: ./config.default
`

See defineConfig for advanced configuration.

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- AWS Local S3
- AWS Local SNS
- AWS Local SQS
- DocumentDB Local Streams
- DynamoDB Local Streams
- Jest
- Vitest

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Hardware and software:

- iMac Pro 2017 (10 cors, 32Gb RAM)
- macOS Ventura (13.2.1)
- NodeJS v18.16.0
- Serverless 3.32.2
- serverless-aws-lambda 4.5.9
- serverless-offline 12.0.4
- serverless-esbuild 1.45.1

Handler:

`js
// src/handlers/visitor.js
let count = 0;
export const handler = async () => {
count++;

return {
statusCode: 200,
body: Visit count ${count},
};
};
`

`yaml
functions:
visitor:
handler: src/handlers/visitor.handler
events:
- http: ANY /visitor
`

| 200 + 200 executions | Time (in seconds) | Memory used (mb) | CPU (core) usage | last invoke response | note |
| --------------------------------------------------------------------------------------- | ---------------------------------------- | ------------------------- | -------------------------- | -------------------- | ----------------------------------- |
| serverless-aws-lambda
cmd: serverless aws-lambda | sequential: 0.644
concurrent: 0.414 | idle: 125
peak: 169 | idle: 0,1%
peak: 15% | Visit count 400 | |
| serverless-offline + serverless-esbuild
cmd: serverless offline --reloadHandler` | sequential: 10.4
concurrent: 2.8 | idle: 110
peak: 3960 | idle: 0,1%
peak: 537% | Visit count 1 | most of concurrent invocations fail |

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See docs.