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07-lambda-layers.md

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Lambda Layers

This article outlines the steps involved in building a node js lambda using lambda layers for library dependencies.

The example will build a lambda function that will return current time using momentjs library. The lambda will not bundle momentjs via package.json, node_modules, as we did in previous tutorial (04-packaging-lambda-with-dependencies) but, will use momentjs via lambda layers.

What is a lambda layer ?

(Source: AWS Docs) : A layer is a ZIP archive that contains libraries, a custom runtime, or other dependencies. With layers, you can use libraries in your function without needing to include them in your deployment package.

(1) Publish the layer

(1.1) Create an empty nodejs project and add momentjs dependency.

> mkdir momentjs-lambda-layer
> cd momentjs-lambda-layer
> npm init -y
> yarn add moment

(1.2) Package momentjs and its node_module dependencies.

  • The packaging should use the folder structure shown below for nodejs lambda layers. This folder structure is a requirement from lambda layers.
  • Move the node_modules into nodejs subdirectory and package them as a zip archive file.
momentjs-lambda-layer.zip
└ nodejs/node_modules/moment

> mkdir -p dist/nodejs
> cp package.json dist/nodejs
> cd dist/nodejs
> yarn --production
> cd ..
> zip -r /tmp/momentjs-lambda-layer.zip nodejs

(1.3) Publish the momentjs as a lambda layer.

Note : Your AWS CLI is assumed to be setup. You can execute aws lambda list-layers --profile "$AWS_PROFILE" to get a response listing the layers. e.g., response

{ "Layers": [] }

We will publish the lambda layer under MIT license. We are not using S3, but directly pushing the zip file that was created earlier. Note :

  • You can publish as many times a layer and they will be automatically published as next version.
> aws lambda publish-layer-version --layer-name "momentjs-lambda-layer" \
  --description "NodeJS module of Moment JS library" \
  --license-info "MIT" \
  --compatible-runtimes "nodejs10.x" \
  --zip-file "fileb:////tmp/momentjs-lambda-layer.zip" \
  --profile "$AWS_PROFILE"

Output:

{
    "LayerVersionArn": "arn:aws:lambda:<AWS_REGION>:<AWS_ACCOUNT_ID>:layer:momentjs-lambda-layer:1",
    "Description": "NodeJS module of Moment JS library",
    "CreatedDate": "2019-11-15T00:00:00.000+0000",
    "LayerArn": "arn:aws:lambda:<AWS_REGION>:<AWS_ACCOUNT_ID>:layer:momentjs-lambda-layer",
    "Content": {
        "CodeSize": 743941,
        "CodeSha256": "aBcDEeFG1H2IjKlM3nOPQrS4Tuv5W6xYZaB+7CdEf8g=",
        "Location": "https://awslambda-ap-se-1-layers.s3.<AWS_REGION>.amazonaws.com/snapshots/<AWS_ACCOUNT_ID>/momentjs-lambda-layer-..."
    },
    "Version": 1,
    "CompatibleRuntimes": [
        "nodejs8.10"
    ],
    "LicenseInfo": "MIT"
}

The LayerVersionArn returned in above step will be used later.

(2) Create the 'CurrentTime' lambda.

(2.1) Create an empty nodejs project.

Note:

  • This example intentionally avoids ES6 import.
  • Move to the same level as the folder momentjs-lambda-layer and create current-time-lambda.
> mkdir current-time-lambda
> cd current-time-lambda
> npm init -y

Create the lambda file with momentjs dependency.

> echo "const moment = require('moment');

exports.handler = (event, context, callback) => {
  const time = moment().format('MMMM Do YYYY, h:mm:ss a');
  callback(null, { time });
};" > currentTimeLambda.js

Note :

  • The lambda source has reference to moment.js, but moment.js is not included in package.json.
  • We will attach the lambda layer that was created earlier to this lambda in following steps.

(2.2) Package the lambda source

Here, we only need the single js file containing the lambda function. The essential purpose of lambda layers - simplify the bundling of lambda and separate the node_modules (dependencies) concern.

> zip -r /tmp/currentTimeLambda.js.zip currentTimeLambda.js

(2.3) Deploy the lambda

aws lambda create-function \
    --region "$AWS_REGION" \
    --function-name currentTimeLambda \
    --handler 'currentTimeLambda.handler' \
    --runtime nodejs10.x \
    --role "$LAMBDA_ROLE_ARN" \
    --zip-file 'fileb:///tmp/currentTimeLambda.js.zip' \
    --profile "$AWS_PROFILE"

On successful creation of lambda, you should see a response similar to the one below.

{
    "TracingConfig": {
        "Mode": "PassThrough"
    },
    "CodeSha256": "aBcDEeFG1H2IjKlM3nOPQrS4Tuv5W6xYZaB+7CdEf8g=",
    "FunctionName": "currentTimeLambda",
    "CodeSize": 14236,
    "RevisionId": "a123b456-789c-0123-4def-g5hij6k789l0",
    "MemorySize": 128,
    "FunctionArn": "arn:aws:lambda:<AWS_REGION>:<AWS_ACCOUNT_ID>:function:currentTimeLambda",
    "Version": "$LATEST",
    "Role": "$LAMBDA_ROLE_ARN",
    "Timeout": 3,
    "LastModified": "2019-11-15T00:00:00.000+0000",
    "Handler": "currentTimeLambda.handler",
    "Runtime": "nodejs8.10",
    "Description": ""
}

Note : If you try executing the lambda function, it will throw error mentioning momentjs library missing.

(3) Update lambda to refer to lambda layer.

(3.1) Attach the lambda layer to the lambda function.

  • For this we need the LayerVersionArn that was returned by AWS when the lambda layer was created. Refer to step 1.4 above.
  • Layers and lambda runtimes compatibility should be checked when this association is done.
> aws lambda update-function-configuration \
  --function-name currentTimeLambda \
  --layers arn:aws:lambda:<AWS_REGION>:<AWS_ACCOUNT_ID>:layer:momentjs-lambda-layer:1 --profile "$AWS_PROFILE"

If the above command of lambda layer association was successful, you should see the layer listed in the lambda details as below.

{
    "Layers": [
        {
            "CodeSize": 743941,
            "Arn": "arn:aws:lambda:<AWS_REGION>:<AWS_ACCOUNT_ID>:layer:momentjs-lambda-layer:1"
        }
    ],
    "FunctionName": "currentTimeLambda",
    "LastModified": "2018-12-05T10:51:28.445+0000",
    "RevisionId": "a123b456-789c-0123-4def-g5hij6k789l0",
    "MemorySize": 128,
    "Version": "$LATEST",
    "Role": "arn:aws:iam::<AWS_ACCOUNT_ID>:role/AWS_ROLE_FOR_LAMBDA",
    "Timeout": 3,
    "Runtime": "nodejs8.10",
    "TracingConfig": {
        "Mode": "PassThrough"
    },
    "CodeSha256": "aBcDEeFG1H2IjKlM3nOPQrS4Tuv5W6xYZaB+7CdEf8g=",
    "Description": "",
    "CodeSize": 14236,
    "FunctionArn": "arn:aws:lambda:<AWS_REGION>:<AWS_ACCOUNT_ID>:function:currentTimeLambda",
    "Handler": "currentTimeLambda.handler"
}

(4) Invoke lambda

(4.1) Invoke the lambda

  • Now, we will invoke the lambda to verify that it uses lambda layer for momentjs dependency.
> aws lambda invoke 
    --function-name currentTimeLambda \
    --profile "$AWS_PROFILE" \
    --log-type Tail \
    --payload '{}' outputfile.txt

Successful invocation should list a response similar to the following.

{
  "LogResult": "A1BCDefghiJKLmnOPQRSt2OWZmMzMwMS0yY2IxLTQ5Y2ItOGJlMS0yMWQwNGZ...TYyLjk2IG1zCQo=",
  "ExecutedVersion": "$LATEST",
  "StatusCode": 200
}

(4.2) View the output

  • To ensure the current time is responded by lambda, view the contents of output.txt file. You should see the time.
> cat outputfile.txt
{"time":"November 18th 2019, 3:44:31 pm"}%

(5) Teardown

Lets remove the lambda layer momentjs-lambda-layer & the Lambda currentTimeLambda we created above.

➜ aws lambda delete-layer-version --layer-name "momentjs-lambda-layer" --version-number 1
➜ aws lambda delete-function --function-name currentTimeLambda --profile "$AWS_PROFILE"

🏁 If you have seen the timestamp, Congrats ! You got your first lambda layer working 🏁

Next: Version Lambda