Send message from Lambda to SQS in Go-CodePudding

I'm looking to send a message to an SQS queue from a Lambda function written in Go, which in the AWS console I have configured so that the SQS queue is connected as a Destination.

The code sample I've seen (here) suggests I need to load a config, create a client and get a queueURL before issuing the message via a call to SendMsg. This approach works fine when running the code locally, but seems unnecessary within the Lambda given I'm connecting the SQS queue in the console. Do I need to tell my Lambda to find the queueURL when I've connected to it as a destination already?

As an aside, I tried this approach but was receiving the following error when running the code from within the Lambda. Invoking the code outside of a Lambda locally would find the queueURL without issue.

{
  "errorMessage": "operation error SQS: GetQueueUrl, https response error StatusCode: 400, RequestID: 2f725471-ec4e-5380-99ed-0f708c1fcfa4, AWS.SimpleQueueService.NonExistentQueue: ",
  "errorType": "OperationError"
}

This led me to look at the flip side, where I have a Lambda which is consuming from the queue and thereby has the SQS queue configured as a trigger. I simply need to iterate over the sqsEvent.Records without having to specify config, client or queueURL as I presume this is handled in the console behind the scenes, i.e.

package main

import (
    "context"
    "fmt"
    "github.com/aws/aws-lambda-go/events"
    "github.com/aws/aws-lambda-go/lambda"
)

func handler(ctx context.Context, sqsEvent events.SQSEvent) error {

    for _, message := range sqsEvent.Records {
        fmt.Printf("The message %s for event source %s = %s \n", message.MessageId, message.EventSource, message.Body)
    }

    return nil
}

func main() {
    lambda.Start(handler)
}

Is there a way of sending a message to a queue from within the Lambda without having to find the queueURL first?

CodePudding user response：

I have configured so that the SQS queue is connected as a Destination.

Sending a message doesn't need you to define a destination per se - destinations are for passing asynchronous Lambda function invocation results. Basically - if you don't explicitly need them (and you know when you do), they won't be what you need.

Give your Lambda permission to send messages to the queue, & use SendMessage using the AWS SDK to send messages. No destinations needed.

AWS.SimpleQueueService.NonExistentQueue

The error message suggests it's not finding the queue, maybe double-check if you're looking in the right region.

I simply need to iterate over the sqsEvent.Records without having to specify config, client or queueURL as I presume this is handled in the console behind the scenes, i.e.

Yes, this is abstracted away - ultimately, your Lambda function is invoked by events and setting Amazon SQS as a trigger allows it to pass events to your function.

Is there a way of sending a message to a queue from within the Lambda without having to find the queueURL first?

Let's rephrase it as - is there a way of sending a letter to someone without having to find their address? Of course not, as we need to know where the letter needs to go.

The same concept applies to SQS queues.