Serverless Express by
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1. DynamoDB Database
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# Serverless Express
Run REST APIs and other web applications using your existing [Node.js](https://nodejs.org/) application framework (Express, Koa, Hapi, Sails, etc.), on top of [AWS Lambda](https://aws.amazon.com/lambda/) and [Amazon API Gateway](https://aws.amazon.com/api-gateway/) or [Azure Function](https://docs.microsoft.com/en-us/azure/azure-functions/).
```bash
npm install @codegenie/serverless-express
```
## Quick Start/Example
Want to get up and running quickly? [Check out our basic starter example](examples/basic-starter-api-gateway-v1) that includes:
- Lambda function
- Express application
- [Serverless Application Model (SAM)](https://github.com/awslabs/serverless-application-model)/[CloudFormation](https://aws.amazon.com/cloudformation/aws-cloudformation-templates/) template
- Helper scripts to configure, deploy, and manage your application
If you want to migrate an existing application to AWS Lambda, it's advised to get the minimal example up and running first, and then copy your application source in.
## AWS
### Minimal Lambda handler wrapper
The only AWS Lambda specific code you need to write is a simple handler like below. All other code you can write as you normally do.
```js
// lambda.js
const serverlessExpress = require('@codegenie/serverless-express')
const app = require('./app')
exports.handler = serverlessExpress({ app })
```
### Async setup Lambda handler
If your application needs to perform some common bootstrap tasks such as connecting to a database before the request is forward to the API, you can use the following pattern (also available in [this example](https://github.com/CodeGenieApp/serverless-express/blob/mainline/examples/basic-starter-api-gateway-v2/src/lambda-async-setup.js)):
```js
// lambda.js
require('source-map-support/register')
const serverlessExpress = require('@codegenie/serverless-express')
const app = require('./app')
let serverlessExpressInstance
function asyncTask () {
return new Promise((resolve) => {
setTimeout(() => resolve('connected to database'), 1000)
})
}
async function setup (event, context) {
const asyncValue = await asyncTask()
console.log(asyncValue)
serverlessExpressInstance = serverlessExpress({ app })
return serverlessExpressInstance(event, context)
}
function handler (event, context) {
if (serverlessExpressInstance) return serverlessExpressInstance(event, context)
return setup(event, context)
}
exports.handler = handler
```
## Azure
### Async Azure Function v3/v4 handler wrapper
The only Azure Function specific code you need to write is a simple `index.js` and a `function.json` like below.
```js
// index.js
const serverlessExpress = require('@codegenie/serverless-express')
const app = require('./app')
const cachedServerlessExpress = serverlessExpress({ app })
module.exports = async function (context, req) {
return cachedServerlessExpress(context, req)
}
```
The _out-binding_ parameter `"name": "$return"` is important for Serverless Express to work.
```json
// function.json
{
"bindings": [
{
"authLevel": "anonymous",
"type": "httpTrigger",
"direction": "in",
"name": "req",
"route": "{*segments}"
},
{
"type": "http",
"direction": "out",
"name": "$return"
}
]
}
```
## 4.x
1. Improved API - Simpler for end-user to use and configure.
1. Promise resolution mode by default. Can specify `resolutionMode` to use `"CONTEXT"` or `"CALLBACK"`
1. Additional event sources - API Gateway V1 (REST API), API Gateway V2 (HTTP API), ALB, Lambda@Edge
1. Custom event source - If you have another event source you'd like to use that we don't natively support, check out the [DynamoDB Example](examples/custom-mapper-dynamodb)
1. Implementation uses mock Request/Response objects instead of running a server listening on a local socket. Thanks to @dougmoscrop from https://github.com/dougmoscrop/serverless-http
1. Automatic `isBase64Encoded` without specifying `binaryMimeTypes`. Use `binarySettings` to customize. Thanks to @dougmoscrop from https://github.com/dougmoscrop/serverless-http
1. `respondWithErrors` makes it easier to debug during development
1. Node.js 12+
1. Improved support for custom domain names
See [UPGRADE.md](UPGRADE.md) to upgrade from aws-serverless-express and @codegenie/serverless-express 3.x
## API
### binarySettings
Determine if the response should be base64 encoded before being returned to the event source, for example, when returning images or compressed files. This is necessary due to API Gateway and other event sources not being capable of handling binary responses directly. The event source is then responsible for turning this back into a binary format before being returned to the client.
By default, this is determined based on the `content-encoding` and `content-type` headers returned by your application. If you need additional control over this, you can specify `binarySettings`.
```js
{
binarySettings: {
isBinary: ({ headers }) => true,
contentTypes: ['image/*'],
contentEncodings: []
}
}
```
Any value you provide here should also be specified on API Gateway API. In SAM, this looks like:
```yaml
ExpressApi:
Type: AWS::Serverless::Api
Properties:
StageName: prod
BinaryMediaTypes: ['image/*']
```
### resolutionMode (default: `'PROMISE'`)
Lambda supports three methods to end the execution and return a result: context, callback, and promise. By default, serverless-express uses promise resolution, but you can specify 'CONTEXT' or 'CALLBACK' if you need to change this. If you specify 'CALLBACK', then `context.callbackWaitsForEmptyEventLoop = false` is also set for you.
```js
serverlessExpress({
app,
resolutionMode: 'CALLBACK'
})
```
### respondWithErrors (default: `process.env.NODE_ENV === 'development'`)
Set this to true to have serverless-express include the error stack trace in the event of an unhandled exception. This is especially useful during development. By default, this is enabled when `NODE_ENV === 'development'` so that the stack trace isn't returned in production.
## Advanced API
### eventSource
serverless-express natively supports API Gateway, ALB, and Lambda@Edge. If you want to use Express with other AWS Services integrated with Lambda you can provide your own custom request/response mappings via `eventSource`. See the [custom-mapper-dynamodb example](examples/custom-mapper-dynamodb).
```js
function requestMapper ({ event }) {
// Your logic here...
return {
method,
path,
headers
}
}
function responseMapper ({
statusCode,
body,
headers,
isBase64Encoded
}) {
// Your logic here...
return {
statusCode,
body,
headers,
isBase64Encoded
}
}
serverlessExpress({
app,
eventSource: {
getRequest: requestMapper,
getResponse: responseMapper
}
})
```
#### eventSourceRoutes
A single function can be configured to handle additional kinds of AWS events:
- SNS
- DynamoDB Streams
- SQS
- EventBridge Events (formerlly CloudWatch Events)
Assuming the following function configuration in `serverless.yml`:
```yaml
functions:
lambda-handler:
handler: src/lambda.handler
events:
- http:
path: /
method: get
- sns:
topicName: my-topic
- stream:
type: dynamodb
arn: arn:aws:dynamodb:us-east-1:012345678990:table/my-table/stream/2021-07-15T15:05:51.683
- sqs:
arn: arn:aws:sqs:us-east-1:012345678990:myQueue
- eventBridge:
pattern:
source:
- aws.cloudformation
```
And the following configuration:
```js
serverlessExpress({
app,
eventSourceRoutes: {
'AWS_SNS': '/sns',
'AWS_DYNAMODB': '/dynamodb',
'AWS_SQS': '/sqs'
'AWS_EVENTBRIDGE': '/eventbridge',
'AWS_KINESIS_DATA_STREAM': '/kinesis',
'AWS_S3': '/s3',
'AWS_STEP_FUNCTIONS': '/step-functions',
'AWS_SELF_MANAGED_KAFKA': '/self-managed-kafka',
}
})
```
Alternatively, to handle only SNS events (the keys in the map are **optional**)
```js
serverlessExpress({
app,
eventSourceRoutes: {
'AWS_SNS': '/sns',
}
})
```
Events will `POST` to the routes configured.
Also, to ensure the events propagated from an internal event and not externally, it is **highly recommended** to
ensure the `Host` header matches:
- SNS: `sns.amazonaws.com`
- DynamoDB: `dynamodb.amazonaws.com`
- SQS: `sqs.amazonaws.com`
- EventBridge: `events.amazonaws.com`
- KinesisDataStream: `kinesis.amazonaws.com`
### logSettings
Specify log settings that are passed to the default logger. Currently, you can only set the log `level`.
```js
{
logSettings: {
level: 'debug' // default: 'error'
}
}
```
### log
Provide a custom `log` object with `info`, `debug` and `error` methods. For example, you could override the default with a [Winston log](https://www.npmjs.com/package/winston) instance.
```js
{
log: {
info (message, additional) {
console.info(message, additional)
},
debug (message, additional) {
console.debug(message, additional)
},
error (message, additional) {
console.error(message, additional)
}
}
}
```
## Accessing the event and context objects
This package exposes a function to easily get the `event` and `context` objects Lambda receives from the event source.
```js
const { getCurrentInvoke } = require('@codegenie/serverless-express')
app.get('/', (req, res) => {
const { event, context } = getCurrentInvoke()
res.json(event)
})
```
## Why run Express in a Serverless environment
- Only pay for what you use
- No infrastructure to manage
- Auto-scaling with zero configuration
- [Usage Plans](http://docs.aws.amazon.com/apigateway/latest/developerguide/api-gateway-api-usage-plans.html)
- [Caching](http://docs.aws.amazon.com/apigateway/latest/developerguide/api-gateway-caching.html)
- [Authorization](http://docs.aws.amazon.com/apigateway/latest/developerguide/apigateway-control-access-to-api.html)
- [Staging](http://docs.aws.amazon.com/apigateway/latest/developerguide/how-to-deploy-api.html)
- [SDK Generation](http://docs.aws.amazon.com/apigateway/latest/developerguide/how-to-generate-sdk.html)
- [API Monitoring](http://docs.aws.amazon.com/apigateway/latest/developerguide/monitoring-cloudwatch.html)
- [Request Validation](http://docs.aws.amazon.com/apigateway/latest/developerguide/api-gateway-method-request-validation.html)
- [Documentation](http://docs.aws.amazon.com/apigateway/latest/developerguide/api-gateway-documenting-api.html)
## Loadtesting
`npx loadtest --rps 100 -k -n 1500 -c 50 https://xxxx.execute-api.us-east-1.amazonaws.com/prod/users`
# AWS Serverless Express is now under the stewardship of Vendia
On 11/30, the AWS Serverless Express library moved from AWS to [Vendia](https://github.com/CodeGenieApp/serverless-express) and will be rebranded to `@codegenie/serverless-express`. Similarly, the [`aws-serverless-express` NPM package](https://www.npmjs.com/package/aws-serverless-express) will be deprecated in favor of [@codegenie/serverless-express](https://www.npmjs.com/package/@codegenie/serverless-express).
[Brett Andrews](https://github.com/brettstack), the original creator of the Serverless Express library, will continue maintaining the repository and give it the attention and care it deserves. At the same time, we will be looking for additional contributors to participate in the development and stewardship of the Serverless Express library. AWS and the [SAM team](https://github.com/aws/aws-sam-cli) will remain involved in an administrative role alongside Vendia, Brett, and the new maintainers that will join the project.
We believe this is the best course of action to ensure that customers using this library get the best possible support in the future. To learn more about this move or become a maintainer of the new Serverless Express library, reach out to us through a GitHub issue on this repository.
Best,
The AWS Serverless team, Brett & the Vendia team