QqsClient.SendMessageAsync without await doesn't work

Question

I have a Lambda function and that lambda function is supposed to send messages to multiple queues in SQS and then exit,

If I add await, then messages are sent to all queues,

var sqsClient = ServerlessHelper.GetAmazonSqsClient();
foreach (var item in items)
{
    await sqsClient.SendMessageAsync(item.QueueUrl, item.Message);
}

But if I remove await from the code, then none of messages are sent to queues. I want to send messages in parallel. But due to await I have function cannot send messages in parallel. I am trying to do something like this,

var sqsClient = ServerlessHelper.GetAmazonSqsClient();
foreach (var item in items)
{
    sqsClient.SendMessageAsync(item.QueueUrl, item.Message);
}
// wait until are messages are sent to queues.

Is it possible to do this?

Answer 1

I'm guessing sqsClient.SendMessageAsync(item.QueueUrl, item.Message); returns a Task since it is an async function?

You need to save the task instances then use Task.WhenAll as in this example.

Answer 2

Yes, it is possible like this:

await Promise.all(
    items.map(item => 
        sqsClient.SendMessageAsync(item.QueueUrl, item.Message)
    )
)

The map function will create an array of promises. This array can be wrapped in a single promise by the Promise.all function, for which you can wait. This way, the promises will be resolved concurrently.