Lambda-local



Lambda-local lets you test NodeJS Amazon Lambda functions on your local machine, by providing a simplistic API and command-line tool.

It does not aim to be perfectly feature proof as projects like serverless-offline or docker-lambda, but rather to remain very light (it still provides a fully built Context, handles all of its parameters and functions, and everything is customizable easily).

The main target are unit tests and running lambda functions locally.

Install

``bash
npm install -g lambda-local
`

Build

`bash
make build
`
Or
`bash
npm install
npm install --only=dev
npm run build
`

Usage

- As an API: You can also use Lambda local directly in a script. For instance, it is interesting in a [MochaJS][1] test suite in order to get test coverage.
- As a command line tool: You can use Lambda-local as a command line tool.

If you're unsure about some definitions, see Definitions for terminology.

About: API

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API accessible with:
`js
const lambdaLocal = require("lambda-local");
`

Or on TypeScript (supported on 1.7.0+):

`js
import lambdaLocal = require("lambda-local");
`

#### lambdaLocal.execute(options)

Executes a lambda given the options object, which is a dictionary where the keys may be:

| Key name | Description |
| --- | --- |
| event|requested event as a json object|
| lambdaPath|requested path to the lambda function|
| lambdaFunc|pass the lambda function. You cannot use it at the same time as lambdaPath|
| profilePath|optional, path to your AWS credentials file|
| profileName|optional, aws profile name. Must be used with |
| lambdaHandler|optional handler name, default to handler|
| region|optional, AWS region, default to us-east-1|| callbackWaitsForEmptyEventLoop|optional, default to false. Setting it to True will wait for an empty loop before returning.|
| timeoutMs|optional, timeout, default to 3000 ms|
| esm|boolean, marks that the script is an ECMAScript module (use import), default false|
| environment|optional, extra environment variables for the lambda|
| envfile|optional, load an environment file before booting|
| envdestroy|optional, destroy added environment on closing, default to false|
| verboseLevel|optional, default 3. Level 2 dismiss handler() text, level 1 dismiss lambda-local text and level 0 dismiss also the result.|
| callback|optional, lambda third parameter [callback][1]. When left out a Promise is returned|
| clientContext|optional, used to populated clientContext property of lambda second parameter (context)

#### lambdaLocal.setLogger(logger)
#### lambdaLocal.getLogger()

Those functions allow to access the winston logger used by lambda-local.

API examples

A lot of examples, especially used among Mocha, may be found in the test files over: here

##### Basic usage: Using Promises

`js
const lambdaLocal = require('lambda-local');

var jsonPayload = {
'key': 1,
'another_key': "Some text"
}

lambdaLocal.execute({
event: jsonPayload,
lambdaPath: path.join(__dirname, 'path_to_index.js'),
profilePath: '~/.aws/credentials',
profileName: 'default',
timeoutMs: 3000
}).then(function(done) {
console.log(done);
}).catch(function(err) {
console.log(err);
});
`

#### Basic usage: using callbacks

`js
const lambdaLocal = require('lambda-local');

var jsonPayload = {
'key': 1,
'another_key': "Some text"
}

lambdaLocal.execute({
event: jsonPayload,
lambdaPath: path.join(__dirname, 'path_to_index.js'),
profilePath: '~/.aws/credentials',
profileName: 'default',
timeoutMs: 3000,
callback: function(err, data) {
if (err) {
console.log(err);
} else {
console.log(data);
}
},
clientContext: JSON.stringify({clientId: 'xxxx'})
});
`

About: CLI

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* -l, --lambda-path (required) Specify Lambda function file name.
* -e, --event-path (required --watch is not in use) Specify event data file name.
* -h, --handler (optional) Lambda function handler name. Default is "handler".
* -t, --timeout (optional) Seconds until lambda function timeout. Default is 3 seconds.
* --esm (optional) Load lambda function as ECMAScript module.
* -r, --region (optional) Sets the AWS region, defaults to us-east-1.
* -P, --profile-path (optional) Read the specified AWS credentials file.
* -p, --profile (optional) Use with -P: Read the AWS profile of the file.
* -E, --environment (optional) Set extra environment variables for the lambda
* --wait-empty-event-loop (optional) Sets callbackWaitsForEmptyEventLoop=True => will wait for an empty loop before returning. This is false by default because our implementation isn\'t perfect and only "emulates" it.
* --envdestroy (optional) Destroy added environment on closing. Defaults to false
* -v, --verboselevel <3/2/1/0> (optional) Default 3. Level 2 dismiss handler() text, level 1 dismiss lambda-local text and level 0 dismiss also the result.
* --envfile (optional) Set extra environment variables from an env file
* --inspect [[host:]port] (optional) Starts lambda-local using the NodeJS inspector (available in nodejs > 8.0.0)
* -W, --watch [port] (optional) Starts lambda-local in watch mode listening to the specified port [1-65535].

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`bash


Simple usage

lambda-local -l index.js -h handler -e examples/s3-put.js

Input environment variables

lambda-local -l index.js -h handler -e examples/s3-put.js -E '{"key":"value","key2":"value2"}'
`

#### Running lambda functions as a HTTP Server (Amazon API Gateway payload format version 2.0.)

A simple way you can run lambda functions locally, without the need to create any special template files (like Serverless plugin and SAM requires), just adding the parameter --watch. It will raise a http server listening to the specified port (default is 8008). You can then call the lambda as mentionned here:
https://docs.aws.amazon.com/lambda/latest/dg/urls-invocation.html

`bash
lambda-local -l examples/handler_gateway2.js -h handler --watch 8008

curl --request POST \
--url http://localhost:8008/ \
--header 'content-type: application/json' \
--data '{
"key1": "value1",
"key2": "value2",
"key3": "value3"
}'
{"message":"This is a response"}
`

You can also use the following format for your event, in order to avoid using the Amazon API Gateway format:
`
{
"event": {
"key1": "value1",
"key2": "value2",
"key3": "value3"
}
}
`

In this case, the event will be passed directly to the handler.

About: Definitions

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Event sample data are placed in examples folder - feel free to use the files in here, or create your own event data.
Event data are just JSON objects exported:

`js
// Sample event data
module.exports = {
foo: "bar"
};
`

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The context object has been sampled from what's visible when running an actual Lambda function on AWS, and the available documentation
They may change the internals of this object, and Lambda-local does not guarantee that this will always be up-to-date with the actual context object.

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As of version 2.0.0, lambda-local no longer packages AWS-SDK in its dependencies. To run a function that makes use of this module, make sure to install it as a dependency in your project.

Other links

- If you are willing to test an app based on the ASK-SDK, have a look at https://github.com/taimos/ask-sdk-test

Development

* Run make to install npm modules. (Required to develop & test lambda-local)
* Run make test to execute the mocha test.
* Run make clean` to reset the repository.

License

This library is released under the MIT license.

[1]: http://docs.aws.amazon.com/lambda/latest/dg/nodejs-prog-model-handler.html