upgrade aws-sdk-go to 1.28.8

[deepthi]

This fixes a problem with vttablet consuming too much memory during a restore from backup when running with option -s3_backup_log_level LogDebugWithRequestRetries

Signed-off-by: deepthi deepthi@planetscale.com

[deepthi]

Tested the following cases with a 250G shard:

1. restore a backup taken with a previous build
2. take a backup with new build and restore
3. restore with -s3_backup_log_level=LogDebugWithRequestRetries

There was no difference in memory usage between 2 & 3.

[rafael]

For completeness, prior to this change, were you able to reproduce the issues we were seeing with the memory leak?

[enisoc]

LGTM

[deepthi]

For completeness, prior to this change, were you able to reproduce the issues we were seeing with the memory leak?

I did not try the older version with -s3_backup_log_level=LogDebugWithRequestRetries which was identified as the culprit by the team at slack.

EDIT[Feb 3, 2020]:
I restored with the older build and reproduced the OOM, so now we can be completely certain that upgrading the library fixes the problem.