Tag: AWS SAM

Console.log output not appearing – AWS SAM Node.js

Hi everyone,

I ran into a bit of an interesting issue today after updating AWS SAM. All of my node log output stopped appearing in my console locally.

For now, there’s a pretty simple workaround:

sam build --use-container && sam local start-api 2>&1 | tr "\r" "\n"

Append 2>&1 | tr “\r” “\n” (including quotes) to your start-api command and you should begin to see the output as expected:

Thanks to the following links for the info:

Adding a Custom Domain Name – AWS SAM

Hi everyone,

It’s been a long time but I’m messing around with AWS SAM again. I’m currently converting www.testerwidgets.com into an AWS SAM application. As part of this I needed to add a custom domain. Unfortunately, the doco on how to do this isn’t great so I’m going to share what ended up working for me just in case it helps someone else.

To start, these are the resources that you’ll need in your template.yaml:

Resources:

  ApiCertificate:
    Type: AWS::CertificateManager::Certificate
    Properties:
      DomainName: !Sub api-${Stage}.YOUR_DOMAIN.com
      ValidationMethod: DNS

  ApiGatewayApi:
    Type: AWS::Serverless::Api
    Properties:
      StageName: !Ref Stage
      # Allows www.YOUR_DOMAIN.com to call these APIs
      # SAM will automatically add AllowMethods with a list of methods for this API
      Cors: "'www.YOUR_DOMAIN.com'"
      EndpointConfiguration: REGIONAL
      Domain:
        DomainName: !Sub api-${Stage}.YOUR_DOMAIN.com
        CertificateArn: !Ref ApiCertificate
        Route53:
          HostedZoneName: "YOUR_DOMAIN.com." # NOTE: The period at the end is required

You’ll also need to make sure your reference the gateway from your function:

  # This lambda function handles is used to test endpoint availability.
  getPing:
    Type: AWS::Serverless::Function
    Properties:
      Handler: src/handlers/get-ping.getPingHandler
      Runtime: nodejs14.x
      Architectures:
        - x86_64
      MemorySize: 128
      Timeout: 30
      Events:
        Api:
          Type: Api
          Properties:
            Path: /ping2 # NOTE: AWS overrides the ping command.
            Method: GET
            RestApiId:
              Ref: ApiGatewayApi # NOTE: Make sure you have this referencing correctly.
      Description: Responds with 'Pong' if successful.

Now when you run AWS deploy it will continue as usual until it gets to the stage of creating your certificate:

Here it is looking for a specific DNS entry in order to confirm that you own the domain. You’ll need to go into Route53 (or whichever other DNS provider you’re using) and add a CNAME entry with the specified details:

Note that your name and value contents should come from the output of the ApiCertificate job (highlighted in the screenshot above).

Once that’s done you’ll need to wait about sixty seconds for the DNS records to propagate within AWS. You should then be able to access your api using the new domain:

Thanks to the follow github post for the pointers in the right direction: https://github.com/aws/aws-sam-cli/issues/2290

aws sam No hosted zones named found

Note that if you get the error above when trying to deploy please ensure that you’ve added the trailing “.” to your Route53 HostedZoneName in the api-gateway in your template.yaml:

Domain:
        DomainName: !Sub api-${Stage}.yourdomain.com
        CertificateArn: !Ref ApiCertificate
        Route53:
          HostedZoneName: "your-domain.com." # NOTE: The period at the end is required

Access to fetch from origin has been blocked by CORS policy – AWS SAM Local

Hi everyone,

I’ve been using AWS SAM local lately and ran into a bit of an issue with CORS. It took a looong time to find a solution that worked for all of my local scenarios so hopefully this will be able to help someone else out.

Access to fetch at 'http://127.0.0.1:3000' from origin 'http://localhost:3001' has been blocked by CORS policy: Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource. If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled.

The error above is fairly typical when working with APIs. The request will work from tools such as postman and fiddler but browsers will block it. These are a few good links that explain why CORS is necessary:
https://medium.com/@electra_chong/what-is-cors-what-is-it-used-for-308cafa4df1a
https://stackoverflow.com/a/29167709/522859

As for the solution, add the following to your template.yml:

  PreFlightFunction:
    Type: AWS::Serverless::Function
    Properties:
      Handler: functions/generic/cors.getPreflightHandler
      Runtime: nodejs8.10
      Events:
        GetEvent:
          Type: Api
          Properties:
            Path: /pages
            Method: options
            RestApiId: !Ref XXXApi
            Auth:
              Authorizer: NONE

If you haven’t already defined your api in your template.yml file there is a default/omitted one created for you. There are a few examples on the AWS github: https://github.com/awslabs/serverless-application-model/blob/release/v1.8.0/examples/2016-10-31/api_cognito_auth/template.yaml

The next thing to do is to create a handler for the options request:


/* Handles retrieving a specific page */
exports.getPreflightHandler = async (event, context, callback) => {
    callback(null, { body: {} }, headers: { 'content-type': 'application/json', 'Access-Control-Allow-Origin': '*', 'Access-Control-Allow-Headers': 'Content-Type,X-Amz-Date,Authorization,X-Api-Key,X-Amz-Security-Token', 'Access-Control-Allow-Methods': 'OPTIONS,GET,POST,PUT,PATCH,DELETE', 'Access-Control-Allow-Credentials': true }, statusCode: 200 })
};

I’ve moved all mine out to some helper methods but the above should be enough to get it working for you. Hopefully the AWS team will have a simpler solution soon but if you run into any issues in the meantime please let me know!

AWS SAM Request Extremely Slow – Fix

Hi everyone,

I’m currently using AWS SAM CLI with NodeJS and was surprised to find that the requests were significantly slower when run locally. Luckily, I came across a post that suggested adding –skip-pull-image to your start-api command:

sam local start-api --skip-pull-image

This brought my requests down to under a second. Thanks to the following link for the info: https://github.com/awslabs/aws-sam-cli/issues/134#issuecomment-406786704

Overriding Global Variables – AWS SAM Local

Hi everyone,

Today I’ve added local overrides to the global variables in my template.yml file. This was pretty finicky – a lot of conflicting suggestions out there unfortunately. These are the settings that ended up working for me.

local-env-var-overrides.json:

{
    "Parameters": {
        "RDS_HOSTNAME_TEST": "192.168.0.31"
    }
}

template.yaml

Globals:
  Function:
    Environment:
      Variables:        
        RDS_HOSTNAME_TEST:
          Type: String
          Default: 'DEFAULT'

aws sam local command:

sam local start-api --env-vars "local-env-var-overrides.json"

create.js

exports.createTrapHandler = async (event, context, callback) => {

	try {

        console.log("RDS_HOSTNAME_TEST: " + process.env.RDS_HOSTNAME_TEST)
        // Outputs: 192.168.0.31

This link ended up being pretty useful: https://www.npmjs.com/package/aws-sam-local

AWS SAM not re-creating DynamoDb Table that was manually deleted – CodeStar

Hi everyone,

I ran into a bit of an issue after deleting a DynamoDb table via the AWS Console that had been created via CloudFormation (using AWS SAM). After deleting it I had expected it to be re-created automatically on the next deploy. Unfortunately this didn’t happen.

I came across the following AWS article that does a pretty good job of summarising the issue: https://aws.amazon.com/premiumsupport/knowledge-center/failing-stack-updates-deleted/

To fix it, I removed all references to the table from my template.yml file (this includes the table definition and any !Ref tags). After pushing this changeset I returned all of the references and re-pushed.

Let me know if you have any issues!

Cheers,
Chris

Error: Invalid value for “–parameter-overrides”: ParameterKey=TABLE_NAME,ParameterValue=CatBreeds is not in valid format. It must look something like ‘ParameterKey=KeyPairName,ParameterValue=MyKey ParameterKey=InstanceType,ParameterValue=t1.micro’ – AWS SAM CLI

Hi everyone,

I ran into the following error while using the AWS SAM Cli:

Error: Invalid value for "--parameter-overrides": ParameterKey=PURPLE_FROG,ParameterValue=CatBreeds is not in valid format. It must look something like 'ParameterKey=KeyPairName,ParameterValue=MyKey ParameterKey=InstanceType,ParameterValue=t1.micro'

This is the command I was running:

sam local start-api --parameter-overrides "ParameterKey=PURPLE_FROG,ParameterValue=CatBreeds"

The error message is unfortunately very misleading. After a fair bit of testing I found that the cause is actually the underscore in the parameter key and has nothing to do with the command format. Renaming all of the parameters to something like “PURPLEFROG” works.

Cheers,
Chris

AWS SAM Cheat Sheet/Quick Reference

Hi everyone,

This will just be a living cheat sheet or quick reference for using AWS SAM with nodejs. I’ll add to it as I find things that are useful or I might need again.

General AWS SAM Info:

Description Example More
Validate template sam validate
Start AWS Sam Locally https://docs.aws.amazon.com/serverless-application-model/latest/developerguide/serverless-quick-start.html
Access config variable in Lambda const CAT_BREED_TABLE = process.env.CAT_BREED_TABLE; https://stackoverflow.com/a/48491845/522859
Dynamically reference another resource in template.yml CAT_BREED_TABLE: !Ref DynamoDbCatBreedTable https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/intrinsic-function-reference-ref.html

Dynamo DB Local Info:

Description Example More
Create table aws dynamodb create-table –table-name CatBreeds –attribute-definitions AttributeName=CatBreedId,AttributeType=S –key-schema AttributeName=CatBreedId,KeyType=HASH –provisioned-throughput ReadCapacityUnits=5,WriteCapacityUnits=5
–endpoint-url http://192.168.0.31:8000 		https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Tools.CLI.html
List Tables aws dynamodb list-tables –endpoint-url http://192.168.0.31:8000 https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Tools.CLI.html
List All Rows in Table aws dynamodb scan –table-name PestinatorTable –endpoint-url http://192.168.0.31:8000 https://stackoverflow.com/a/52236600/522859

Node.js Info:

Description Example More
Run tests npm test –

Create DynamoDB Table – AWS CLI

Hi everyone,

A quick example of how to create a dynamodb table using the AWS CLI:

aws dynamodb create-table --table-name CatBreeds --attribute-definitions AttributeName=CatBreedId,AttributeType=S --key-schema AttributeName=CatBreedId,KeyType=HASH --provisioned-throughput ReadCapacityUnits=5,WriteCapacityUnits=5

For more info the following AWS page helped me: https://docs.aws.amazon.com/cli/latest/reference/dynamodb/create-table.html

Check if Running Locally – AWS SAM & NodeJS

Hi everyone,

Just a quick post on how to check if code is being run locally with AWS SAM and NodeJS:

// 8+
isRunningLocally = () => {
    return process.env.AWS_SAM_LOCAL === 'true';
}

// 6+
function isRunningLocally() {
    return process.env.AWS_SAM_LOCAL === 'true';
}