Fixing the follower checkpoint updation in follower stats API

[gbbafna]

Summary : We need to update followerCheckpoint after writing to the follower index.
Currently, we are not waiting for the writes and updating it with soon-to-be stale values

Signed-off-by: Gaurav Bafna gbbafna@amazon.com

Description

Correctly updating follower_stats at two places :

1. At start of replication , reading it from shard itself.
2. After every write, again updating it from shard itself.

Issues Resolved

431

Check List

• New functionality includes testing.
  • All tests pass
• New functionality has been documented.
  • New functionality has javadoc added
• Commits are signed per the DCO using --signoff

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.
For more information on following Developer Certificate of Origin and signing off your commits, please check here.

[ankitkala]

LGTM

[opensearch-trigger-bot]

The backport to 1.1 failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add .worktrees/backport-1.1 1.1
# Navigate to the new working tree
cd .worktrees/backport-1.1
# Create a new branch
git switch --create backport/backport-438-to-1.1
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 6130d6feda5075a695bc384b2702a76d4db383a6
# Push it to GitHub
git push --set-upstream origin backport/backport-438-to-1.1
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-1.1

Then, create a pull request where the base branch is 1.1 and the compare/head branch is backport/backport-438-to-1.1.