Batch methods

[CallumNZ]

Changes proposed in this pull request:

• Add methods for SQS batch requests

Production Changes

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• None

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[wilsonjord]

I suspect it would be more complicated, but since []string is being passed to SendBatchN, perhaps instead of returning a slice of failed bodies, a slice of failed indexes could done? Returning body copies seems inefficient.

[wilsonjord]

issue: error handling not quite as clean as it could be; seems to me that I need to check the Info field for empty, before knowing how to handle the error, which seems a little backwards. I also don't know why the fields aren't simply exported. Would you consider wrapping the general err, and separating it out from "partial message failure"? Something like:

var SendBatchPartialError = errors.New("partial message failure")

type SendBatchError struct {
    Err error
    Info []SendBatchResultErrorEntry
}

func (e *SendBatchError) Unwrap() error {
    return e.Err
}

void main() {
    err := sqs.SendBatch(payload)
    if errors.Is(err, SendBatchPartialError) {
        // deal with err.Info
    } else if err != nil {
        // general error, I can should be able to access wrapped error if desired
    }
}

[wilsonjord]

question: why this if we know message is too big?

[CallumNZ]

@wilsonjord an example of using it: https://github.com/GeoNet/tilde/blob/b4cd55a4a5dd930bcfe78cc6034de4a27ff7788c/cmd/tilde-router/sqs-batcher.go#L59

The current idea is:

If there's an HTTP error, all elements of batch are added to Info.
If there's a partial error, just the failed elements of batch are added to Info.

So, if there's any sort of error, the user will be looping over Info to see which elements failed.

[bpeng]

Looks good