Lambda layers node_modules

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Solution 1

How are you running your lambda? If via sam cli, something like the below has worked for me as my template.yaml ...

example template

AWSTemplateFormatVersion: 2010-09-09
Transform: AWS::Serverless-2016-10-31
Description: example of node.js lambda function using layer for dependencies

Resources:

  ExampleFunction:
    Type: AWS::Serverless::Function
    Properties:
      Runtime: nodejs8.10
      CodeUri: nodejs/
      Handler: src/event.handler
      Layers:
        - !Ref NodeModulesLayer

  NodeModulesLayer:
    Type: AWS::Serverless::LayerVersion
    Properties:
      Description: full set of function dependencies
      ContentUri: ./
      CompatibleRuntimes:
        - nodejs6.10
        - nodejs8.10
      LicenseInfo: 'Available under the MIT-0 license.'
      RetentionPolicy: Retain

pointing to local layer

The SAM developer guide includes a page on Working with Layers. At the time I'm writing this, they don't really get into how to reference layers at local file paths, and instead focus on references to remotely hosted layers.

The aspect I found tricky is that the directory structure of a node.js layer is expected to be ...

nodejs/
  node_modules/

... which means that in order for your locally installed node_modules directory to work as a layer, your package.json file must be nested inside a folder named nodejs.

Note the paths in the above example template.yaml:

  1. ExampleFunction.Properties.CodeUri is set to nodejs/
  2. ExampleFunction.Properties.Handler should be set to the path to your handler file, relative to nodejs/.
  3. NodeModulesLayer.Properties.ContentUri is set to the folder that contains both the template.yaml file and the nodejs dir.

Which means my example is assuming the following structure ...

nodejs/
  node_modules/
  src/
    event.js
  package.json
template.yaml

preserve sam build support

One additional gotcha to be wary of ...

With respect to defining your function resource in template.yaml, there's some "flexibility" in terms of which parts of the path you put in CodeUri vs Handler. In some cases, doing ...

    Properties:
      CodeUri: nodejs/src/
      Handler: event.handler

... works just as well as doing ...

    Properties:
      CodeUri: nodejs/
      Handler: src/event.handler

BUT, if you're using the sam build command, the former will NOT work. That command expects to find package.json inside of the CodeUri directory. So, stick with CodeUri: nodejs/ and use the Handler value to navigate through any additional folder hierarchy necessary to reaching your handler.

Solution 2

Try this, simple example how to set up lambda layer in nodejs:

https://medium.com/@anjanava.biswas/nodejs-runtime-environment-with-aws-lambda-layers-f3914613e20e

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James Gunn
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James Gunn

Updated on September 15, 2022

Comments

  • James Gunn
    James Gunn about 1 year

    I am creating a lambda layer, bundling up some dependencies, including node_modules. I am successfully creating a layer but when i try to require a module from my code, the console is telling me that the module cannot be found. Here is the code

    var Promise = require('promise');
    module.exports.handler = function(event, context, callback) {   
      new Promise(function (resolve, reject) {
        setTimeout(function() {
          callback(null, "helloWorld2");
        }, 9000);
      });
    };
    

    How can I reference node modules from a layer???

    • James Gunn
      James Gunn almost 5 years
      What if i'm using an older version of node? I'm well aware that promises are built in to newer versions of node. please keep on topic
  • Naphtali Gilead
    Naphtali Gilead about 4 years
    This works great when I build, but when I pack it using sam, it packs the node_modules twice. Once into my function code and the other into a layer. @RH Becker, do you have a suggestion on how to resolve this?
  • RH Becker
    RH Becker about 4 years
    @NaphtaliGilead: I don't. My recent work hasn't involved sam. If, when I eventually get back to it, I come across any good approaches, I'll share. Please do the same, if you figure it out.