Serve Binary responses via ALB and Lambda Integration

Question

AWS just announced a new feature Invoking Lambda functions using Application Loadbalancers. This is great news as we don't have to configure all those mappings for API gateway just to get a simple response from my lambda function.

We have an image resizing service running on lambda via API gateway. I am wondering if we can replace API gateway with ALB. The way it works now we have to send a base64 encoded image to api gateway which in return converts it to a binary and send back to our clients.

If we were to replace API gateway with ALB how would we be serving images/binary responses what will be the needed changes we have to do to our existing infrastructure.

score 3 · Answer 1 · answered Dec 17 '18 at 18:14

if you haven't figured out yet, you can provide binary data from your Lambda function in the same way you did for API GW. ALB also supports the same "isBase64Encode" flag that can be set in the response JSON. ALB b64 decodes the body if that flag is set.

From the documentation: { "statusCode": 200, "statusDescription": "HTTP OK", **"isBase64Encoded": False,** "headers": { "server": "my-server", "set-cookie": "name=value", "Content-Type": "text/html; charset=utf-8" }, "body": "Welcome" }

Basically, just b64 encode your body and set that flag, ALB will decode it for you, make sure the content type is set correctly.

score 2 · Accepted Answer · answered Dec 11 '18 at 06:48

Receive Events From the Load Balancer is the Use Case:

Now Application load balancer supports Lambda invocation for requests over both HTTP and HTTPS. If the content type is one of the following types, the load balancer sends the body to the Lambda function as is and sets isBase64Encoded to false: text/*, application/json, application/javascript, and application/xml. For all other types, the load balancer Base64 encodes the body and sets isBase64Encoded to true

The following is an example event.

{
    "requestContext": {
     "elb": {
     "targetGroupArn":
     "arn:awscn:elasticloadbalancing:region:123456789012:targetgroup/my-target- group/6d0ecf831eec9f09" // ALB reference
          }
          },
"httpMethod": "GET",
"path": "/",
"queryStringParameters": {parameters},
"headers": {
"accept": "text/html,application/xhtml+xml",
"accept-language": "en-US,en;q=0.8",
"content-type": "text/plain",
"cookie": "cookies",
"host": "lambda-846800462-us-east-2.elb.amazonaws.com", //this is where Lambda CNAME is declared
"user-agent": "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_6)",
"x-amzn-trace-id": "Root=1-5bdb40ca-556d8b0c50dc66f0511bf520",
"x-forwarded-for": "72.21.198.66",
"x-forwarded-port": "443",
"x-forwarded-proto": "https"
      },
"isBase64Encoded": false,
"body": "request_body"
 }

following Official AWS Guide which will describe your use case

score -1 · Answer 3 · answered Dec 07 '18 at 07:25

-1

In my view that way ALB will invoke Lambda function is application path based routing. let's say, you application has a path /imageprocessing so when your client will access the said resource ALB will call LAMBDA function as your target.

now with this new feature, you have a capability to use ALB or Gateway or both. New capability makes easy to extend your existing service now.

answered Dec 07 '18 at 07:25

Yash Bindlish

560
5
15

Thanks @yash for your response. The question was how to server images/binary content via ALB. Currently with API gateway and Lambda integration lambda function will return a base64 encoded image object which will be converted to binary blob by api gateway. So, how we will achieve the same with ALB and Lambda. – Umer Dec 11 '18 at 06:33
@Umer i have just posted the example and detailed description as another answer to your use case. i hope this will help – Yash Bindlish Dec 11 '18 at 06:50

Serve Binary responses via ALB and Lambda Integration

3 Answers3