Nil de-reference panic from attempts to access nil Retryer provider of Request object

[CMLivingston]

Companion issue for aws/aws-dax-go#18

Version of AWS SDK for Go?

v1.25.9

Version of Go (go version)?

go1.12.9 darwin/amd64

What issue did you see?

Nil-dereference panics from attempts to access nil retryer function r.MaxRetries() of request object here: https://github.com/aws/aws-sdk-go/blob/master/aws/request/request.go#L557
This a result of passing a nil retryer to NewDaxRequest in aws-dax-go as described in aws/aws-dax-go#18.

Steps to reproduce

Use dax go client to read from a dynamo table and force a server error from Dynamo. For us, we set read capacity to 1 read unit and started getting throttled event errors from Dynamo.

A potential solution is to ensure all accesses of r.MaxRetries() only happen if aws.BoolValue(r.Retryable) is true:
https://github.com/aws/aws-sdk-go/blob/master/aws/request/request.go#L557

We also filed against the dax go project as a fix in both places would make dep management much easier for consumers of both libraries.

[diehlaws]

Hi @CMLivingston, thanks for reaching out to us about this. Unfortunately I haven't been able to reproduce this using the sample code for aws/aws-dax-go modified to send GetItem requests instead of PutItem - I'm able to elicit ProvisionedThroughputExceededException errors without the client panicking on a nil dereference. Can you provide a code sample that exhibits this behavior so we can better understand how you're running into this?

[VasilyFomin]

In order to reproduce it you have to do the following:

cfg := dax.
cfg.HostPorts = []string{endpoint}
cfg.Region = region
client := dax.New(cfg)
in := &dynamodb.GetItemInput{
    TableName: aws.String(table),
    Key:       key,
}
r, _ := client.GetItemRequest(in)
r.Send()

so the key point here is to use Request.Send method, which we actually don't use in our examples

[jasdel]

Thanks for letting us know about this issue. I've merged in PR #2934 which patches the ability of the SDK to more cleanly handle a nil Retryer value. This change will be included in our next tagged release.

[CMLivingston]

Thanks!