Support for golang lambda functions

[wolfgangmeyers]

AWS now offers official support for golang lambda functions: https://aws.amazon.com/blogs/compute/announcing-go-support-for-aws-lambda/

Any idea on how to make these work with localstack? If they're not yet supported, where would be the best place to look if I wanted to add support?

[HoneyryderChuck]

+1, I'd be definitely interested in this

[wolfgangmeyers]

In case in helps anyone else, I've worked around this for now by implementing a webhook wrapper around the lambda handler that simulates a direct sns->lambda invocation. It handles subscription confirmation requests, but as far as I've seen a confirmation request isn't ever sent by localstack. This example uses the gin framework for http handling:

// SNSPayload represents the expected JSON formation from
// SNS that would be delivered to a webhook
type SNSPayload struct {
	Type         string // SubscriptionConfirmation | Notification
	SubscribeURL string
	Message      string
}

// Start up a replication webhook to fill in for lack of go lambda support in localstack
func webhook() {
	// Set environment variables that lambda task will expect
	os.Setenv("AWS_REGION", *awsRegion)
	os.Setenv("AWS_HOST", *awsHost)
	os.Setenv("AWS_PREFIX", *awsPrefix)

	r := gin.New()
	// GET / supports a check from the subscription tool to make sure
	// that the webhook is up before proceeding with the sns subscription
	r.GET("/", func(ctx *gin.Context) {
		ctx.String(http.StatusOK, "UP!")
	})
	r.POST("/", func(ctx *gin.Context) {
		// This is either subcription confirmation or a replication event is being sent
		snsPayload := &SNSPayload{}
		err := ctx.BindJSON(snsPayload)
		if snsPayload.Type == "SubscriptionConfirmation" {
			logger.Info("Handling subscription confirmation")
			_, err = http.Get(snsPayload.SubscribeURL)
			if err != nil {
				logger.Errorf("Error confirming subscription: %v", err.Error())
			}
		} else {
			// Simulate a normal SNS invocation of lambda
			err = replication.Handler(events.SNSEvent{
				Records: []events.SNSEventRecord{
					events.SNSEventRecord{
						SNS: events.SNSEntity{
							Message: snsPayload.Message,
						},
					},
				},
			})
			if err != nil {
				logger.Errorf("Error invoking lambda function: %v", err.Error())
			}
		}
	})
	addr := fmt.Sprintf(":%v", *appPort)
	logger.Infof("Starting up on %v", addr)
	http.ListenAndServe(addr, r)
}

[whummer]

lambci/docker-lambda recently added support for Go Lambda functions, see this example: https://github.com/lambci/docker-lambda/blob/master/examples/go1.x/handler.go .

Since we're already using the lambci Docker images for Java/Node/Python, it should be fairly straightforward to add support for Go. @wolfgangmeyers @HoneyryderChuck would you be able to look into into this? I'd be happy to help out where needed. This is a good starting point: lambda_executors.py

[wolfgangmeyers]

@whummer Thanks for the help on this. I looked at lambda_executors.py and lambda_api.py, and after some digging, it seems that the runtime that is passed to lambci comes from the create_function api:

localstack/localstack/services/awslambda/lambda_api.py

Line 453 in 2be88f5

func_details.runtime = data['Runtime']

It appears that lambci is downloaded automatically by docker, so I think that should just work if the runtime is configured when creating the function. We might need to configure the correct executor here when the function code is updated:

localstack/localstack/services/awslambda/lambda_api.py

Line 310 in 2be88f5

def set_function_code(code, lambda_name):

[wolfgangmeyers]

I'll try to see if I can get this working when I have time

[wolfgangmeyers]

@whummer I've made some progress. I've made some local changes so that the handler doesn't get a .py added to it, set up the LAMBDA_EXECUTOR=docker. The lambda executor seems to be attempting to use lambci now to run the task, but I'm hitting an error:

localstack_1  | 2018-02-16T19:27:12:WARNING:localstack.services.awslambda.lambda_api: Error executing Lambda function: Lambda process returned error status code: 1. Output:
localstack_1  | Unable to find image 'lambci/lambda:go1.x' locally
localstack_1  | go1.x: Pulling from lambci/lambda
localstack_1  | 5be106c3813f: Pulling fs layer
localstack_1  | e240967675e1: Pulling fs layer
localstack_1  | 5448b9eca4b0: Pulling fs layer
localstack_1  | 3bc1caac25ba: Pulling fs layer
localstack_1  | 3bc1caac25ba: Waiting
localstack_1  | e240967675e1: Verifying Checksum
localstack_1  | e240967675e1: Download complete
localstack_1  | 5448b9eca4b0: Verifying Checksum
localstack_1  | 5448b9eca4b0: Download complete
localstack_1  | 3bc1caac25ba: Verifying Checksum
localstack_1  | 3bc1caac25ba: Download complete
localstack_1  | 5be106c3813f: Verifying Checksum
localstack_1  | 5be106c3813f: Download complete
localstack_1  | 5be106c3813f: Pull complete
localstack_1  | e240967675e1: Pull complete
localstack_1  | 5448b9eca4b0: Pull complete
localstack_1  | 3bc1caac25ba: Pull complete
localstack_1  | Digest: sha256:d77adf847c45dcb5fae3cd93283447fad3f3d51ead024aed0c866a407a206e7c
localstack_1  | Status: Downloaded newer image for lambci/lambda:go1.x
localstack_1  | START RequestId: 7519261c-3b1f-1f6d-3d12-5144c6c5d86b Version: $LATEST
localstack_1  | END RequestId: 7519261c-3b1f-1f6d-3d12-5144c6c5d86b
localstack_1  | REPORT RequestId: 7519261c-3b1f-1f6d-3d12-5144c6c5d86b  Duration: 3.96 ms       Billed Duration: 100 ms Memory Size: 1536 MB   Max Memory Used: 6 MB
localstack_1  | {
localstack_1  |   "errorMessage": "fork/exec /var/task/my-go-task: permission denied",
localstack_1  |   "errorType": "PathError"
localstack_1  | }
localstack_1  |  Traceback (most recent call last):
localstack_1  |   File "/opt/code/localstack/localstack/services/awslambda/lambda_api.py", line 255, in run_lambda
localstack_1  |     event, context=context, version=version, async=async)
localstack_1  |   File "/opt/code/localstack/localstack/services/awslambda/lambda_executors.py", line 130, in execute
localstack_1  |     result, log_output = self.run_lambda_executor(cmd, environment, async)
localstack_1  |   File "/opt/code/localstack/localstack/services/awslambda/lambda_executors.py", line 67, in run_lambda_executor
localstack_1  |     (return_code, log_output))

[wolfgangmeyers]

Similar issue reported here on a different project - aws/aws-sam-cli#274

[wolfgangmeyers]

I printed out the command that is running in order to launch docker:

localstack.services.awslambda.lambda_executors: CONTAINER_ID="$(docker create  -e AWS_LAMBDA_EVENT_BODY="$AWS_LAMBDA_EVENT_BODY" -e LOCALSTACK_HOSTNAME="$LOCALSTACK_HOSTNAME" -e HOSTNAME="$HOSTNAME" "lambci/lambda:go1.x" "my-go-task")";docker cp "/tmp/localstack/zipfile.1c5caf40/." "$CONTAINER_ID:/var/task";docker start -a "$CONTAINER_ID";

Going to see if I can run this outside of localstack and get more details

[wolfgangmeyers]

So I was able to take one of the stopped containers and recreate it with docker commit and launched it with bash as the entrypoint. I've confirmed that the executable permissions of the handler are gone, and that's why the patherror is being returned. Somewhere in the process of unzipping/copying the permissions are being lost.

[wolfgangmeyers]

Docs for docker cp state that file permission are preserved, so I'm going to look over the unzipping code - https://docs.docker.com/engine/reference/commandline/cp/#extended-description

[wolfgangmeyers]

Looks like the problem is with the behavior of ZipFile.extractall - I found a solution, will update the code: https://www.burgundywall.com/post/preserving-file-perms-with-python-zipfile-module

[wolfgangmeyers]

I think it worked...? I can't seem to get any kind of output from the task, just a statuscode. But the process seems to be executing normally now.

$ aws lambda create-function --endpoint="http://localhost:4574"  --function-name="hello" --runtime="go1.x"--handler="hello" --role="foobar" --zip-file=fileb://hello.zip
{
    "FunctionName": "hello",
    "FunctionArn": "arn:aws:lambda:us-east-1:000000000000:function:hello",
    "Runtime": "go1.x",
    "Role": "foobar",
    "Handler": "hello",
    "VpcConfig": {
        "SubnetIds": [
            null
        ],
        "SecurityGroupIds": [
            null
        ]
    },
    "Environment": {
        "Variables": {},
        "Error": {}
    },
    "TracingConfig": {}
}
$ aws lambda --endpoint="http://localhost:4574" invoke --function-name=hello --payload='{"Name": "Wolfgang"}' test
{
    "StatusCode": 200
}