How to share a common file in all lambda functions

3
votes

I have some lambda functions(node.js) in AWS, that will connect to postgresql and doing some query and get the results back, so i am trying to make one configuration file for database which has the user, password, database name, port ... So what will be the best way to share a common configuration file to all lambda function?

3
node.jsamazon-web-servicesamazon-s3aws-lambda
docs.aws.amazon.com/lambda/latest/dg/env_variables.html - Jack Ryan
@JackRyan this i have to update in every lambda function, if i have any change in my db configuration then i have to go to every lambda function and change right? i am looking something like when i change in one place that will give effect in all lambda functions. - Developer

3 Answers

2
votes

It is possible to share common files between different Lambda Functions using Layers. You can create a zip file for the Layer pretty much the same way you do that for a Function.

The layer package will look more or less like this:

your-lambda-layer.zip
└ nodejs/node_modules/shared-package

In the code it can be referenced like this:

const shared = require('shared-package');

The shared-package can contain your code or configurations.

1
votes

AWS Provides two services for this purpose.

  1. AWS Secrets Manager
  2. AWS Systems Manager Parameter Store

AWS Secrets Manager is the latest service which has version controlled secrets and automatically rotates keys.

You can either store is as individual keys or combine all keys, store them as one key.

Secrets Manager Example:

https://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/SecretsManager.html#getSecretValue-property

var params = {
  SecretId: "MyTestDatabaseSecret", 
  VersionStage: "AWSPREVIOUS"
 };
 secretsmanager.getSecretValue(params, function(err, data) {
   if (err) console.log(err, err.stack); // an error occurred
   else     console.log(data);           // successful response
   /*
   data = {
    ARN: "arn:aws:secretsmanager:us-west-2:123456789012:secret:MyTestDatabaseSecret-a1b2c3", 
    CreatedDate: <Date Representation>, 
    Name: "MyTestDatabaseSecret", 
    SecretString: "{\n  \"username\":\"david\",\n  \"password\":\"BnQw&XDWgaEeT9XGTT29\"\n}\n", 
    VersionId: "EXAMPLE1-90ab-cdef-fedc-ba987SECRET1", 
    VersionStages: [
       "AWSPREVIOUS"
    ]
   }
   */
 });

Systems Manager Parameter Store:

https://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/SSM.html#getParameter-property

var params = {
  Name: 'STRING_VALUE', /* required */
  WithDecryption: true || false
};
ssm.getParameter(params, function(err, data) {
  if (err) console.log(err, err.stack); // an error occurred
  else     console.log(data);           // successful response
});

EDIT1:

For sharing common files from a common storage, it is not possible as now. You can store the file in s3 and pull from there. It is going to have a heavy cold start.

1
votes

Define your shared code in a AWS Lambda Layer using AWS::Lambda::LayerVersion or AWS::Serverless::LayerVersion and then reference to it in your lambda functions. For example with AWS SAM :

  MyFunction:
    Type: AWS::Serverless::Function
    Properties:
      CodeUri: function_code/
      Handler: app.lambda_handler
      Runtime: nodejs8.10
      Layers:
        - !Ref MySharedLayer
  MySharedLayer:
    Type: AWS::Serverless::LayerVersion
    Properties:
      LayerName: SharedLayerName
      Description: Some shared code
      ContentUri: layer_code/
      CompatibleRuntimes:
        - nodejs8.10
      LicenseInfo: 'My License'
      RetentionPolicy: Retain

The layer code will be available in the /opt folder and can be included in your lambda functions.