simple-lambda-client

A simple, convenient way to invoke aws lambda functions with best practices.

Best practices:

• optional logDebug of input and output
• throw an error if response contains an error object

install

npm install --save simple-lambda-client

use

import { invokeLambdaFunction } from 'simple-lambda-client';

const service = 'svc-jobs';
const stage = getStage();

const getJobByUuid = (event: { uuid: string }): Promise<{ job: Job | null }> =>
  invokeLambdaFunction({ service, stage, function: 'getJobByUuid', event });

const getJobsByPostal = (event: { postal: string }): Promise<{ jobs: Job[] }> =>
  invokeLambdaFunction({ service, stage, function: 'getJobsByPostal', event });

// ...

export const svcJobs = {
  getJobByUuid,
  getJobsByPostal
}

details

invoke

simple-lambda-client exports a function that lets you invoke lambda functions with best practices.

You can use this function directly if you want...

import { invokeLambdaFunction } from 'simple-lambda-client';

const result = await invokeLambdaFunction({ service, stage, function, event });
// ...do amazing things with result...

type

But you'll probably want to create a reusable method with typedefs

export const getJobByUuid = (event: { uuid: string }) =>
  invokeLambdaFunction<{ job: Job | null }>({ service, stage, function: 'getJobByUuid', event });

Which makes using that a lot easier

const { job } = await getJobByUuid({ uuid: '__uuid__' });
// ...do amazing things with result...

namespace

You may also want to build a full representation of some lambda service under a namespace

export const svcJobs = {
  getJobByUuid,
  // ...other methods...
};

This adds extra context about "where" the methods lambdas invoking is coming from

import { svcJobs } from '../path/to/client';

const { job } = await svcJobs.getJobByUuid({ uuid: '__uuid__' });
// ...do amazing things with result...

features

errors

When this library detects that the lambda you called has thrown an error, it automatically parses it and throws an error of class LambdaInvocationError

For example

import { invokeLambdaFunction, LambdaInvocationError } from 'simple-lambda-client';

try {
  await invokeLambdaFunction({
    service: 'svc-does-not-exist', // 👈 assume this will cause an error
    function: 'doAwesomeThing',
    stage: 'dev',
    event: {},
  });
} catch (error) {
  expect(error).toBeInstanceOf(LambdaInvocationError) // 👈 error will be an instance of this class
}

logging

When given a logDebug method, this library emits input and output logs with best practices, to make debugging a breeze.

For example

await invokeLambdaFunction({
  service: 'svc-oceans',
  function: 'cleanup',
  stage: 'dev',
  event: {},
  logDebug: console.log, // 👈 will now emit logs to the console
});

caching

When given a cache instance, this library will wrap the lambda invocation with-simple-caching

For example

import { createCache } from 'simple-im-memory-cache';

await invokeLambdaFunction({
  service: 'svc-oceans',
  function: 'cleanup',
  stage: 'dev',
  event: {},
  cache: createCache(), // 👈 will now cache the response, with a key of [service, function, stage, event]
});

tips

lambda permissions

if you're using this client from inside a lambda, ensure that this lambda has permission to invoke other lambdas

# serverless.yml
iamRoleStatements:
  - Effect: Allow
    Action:
      - lambda:InvokeFunction
      - lambda:InvokeAsync
    Resource: '*' # TODO: constrain to a specific account, region, service, and stage