Establish seed node connections in async during node bootstrap

[ankitkala]

Description

Establish seed node connections in async during node bootstrap

Related Issues

Resolves #7950

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
• Commit changes are listed out in CHANGELOG.md file (See: Changelog)

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.

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: FAILURE ❌
• URL: https://build.ci.opensearch.org/job/gradle-check/17425/
• CommitID: 628efa9
  Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green.
  Is the failure a flaky test unrelated to your change?

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: FAILURE ❌
• URL: https://build.ci.opensearch.org/job/gradle-check/17428/
• CommitID: 60f96b9
  Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green.
  Is the failure a flaky test unrelated to your change?

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: FAILURE ❌
• URL: https://build.ci.opensearch.org/job/gradle-check/17438/
• CommitID: 91fe701
  Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green.
  Is the failure a flaky test unrelated to your change?

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: FAILURE ❌
• URL: https://build.ci.opensearch.org/job/gradle-check/17439/
• CommitID: adc95ad
  Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green.
  Is the failure a flaky test unrelated to your change?

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: UNSTABLE ❕
• TEST FAILURES:

      1 org.opensearch.search.backpressure.SearchBackpressureIT.testSearchShardTaskCancellationWithHighCpu
      1 org.opensearch.remotestore.RemoteStoreRefreshListenerIT.testRemoteRefreshRetryOnFailure

• URL: https://build.ci.opensearch.org/job/gradle-check/17442/
• CommitID: 5ef6976
  Please review all flaky tests that succeeded after retry and create an issue if one does not already exist to track the flaky failure.

[codecov]

Codecov Report

Merging #8038 (5ef6976) into main (bf3cf71) will decrease coverage by 0.10%.
The diff coverage is 100.00%.

❗ Current head 5ef6976 differs from pull request most recent head ee815c6. Consider uploading reports for the commit ee815c6 to get more accurate results

@@             Coverage Diff              @@
##               main    #8038      +/-   ##
============================================
- Coverage     70.92%   70.83%   -0.10%     
+ Complexity    56636    56575      -61     
============================================
  Files          4721     4721              
  Lines        267514   267470      -44     
  Branches      39212    39210       -2     
============================================
- Hits         189745   189454     -291     
- Misses        61770    62016     +246     
- Partials      15999    16000       +1     

Impacted Files	Coverage Δ
...org/opensearch/transport/RemoteClusterService.java	86.79% <100.00%> (+4.69%)	⬆️
...ava/org/opensearch/transport/TransportService.java	80.03% <100.00%> (+0.46%)	⬆️

... and 454 files with indirect coverage changes

[krishna-ggk]

So one consequence of this could be that node is up while remote connection establishment is still in progress in which case any outbound cross-cluster requests could fail with "no such remote" right?

Could this also impact CCR?

[Bukhtawar]

The one common problem with async connection handling is the race around connection and disconnection. See #4874. Want to ensure we don't run into a similar issue going forward

[shwetathareja]

@ankitkala can you please highlight the implication of moving the remote connection to async. As i understand today also there is no guarantee that connection would be established in sync in 10secs. What happens in case a CCR/ CCS request comes. What is the error thrown?

[ankitkala]

So one consequence of this could be that node is up while remote connection establishment is still in progress in which case any outbound cross-cluster requests could fail with "no such remote" right?

Could this also impact CCR?

@ankitkala can you please highlight the implication of moving the remote connection to async. As i understand today also there is no guarantee that connection would be established in sync in 10secs. What happens in case a CCR/ CCS request comes. What is the error thrown?

This should not impact any of the cross cluster calls. For each such call, Remote cluster client invokes a blocking call to remoteClusterService.ensureConnected to ensure that the connection is established here (ensureConnected and connectImpl)
This code change makes the connect as async only during node bootstrap. Cross cluster calls and Seed node updates aren't affected by this change.

[ankitkala]

The one common problem with async connection handling is the race around connection and disconnection. See #4874. Want to ensure we don't run into a similar issue going forward

Thanks. I took a cursory look at the issue above.
This change isn't modifying the behaviour of how the connection is established/disconnected. So I don't expect any issues there.

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: UNSTABLE ❕
• TEST FAILURES:

      1 org.opensearch.remotestore.SegmentReplicationUsingRemoteStoreIT.testRestartPrimary
      1 org.opensearch.remotestore.RemoteStoreRefreshListenerIT.testRemoteRefreshRetryOnFailure

• URL: https://build.ci.opensearch.org/job/gradle-check/17552/
• CommitID: 35cede2
  Please review all flaky tests that succeeded after retry and create an issue if one does not already exist to track the flaky failure.

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: UNSTABLE ❕
• TEST FAILURES:

      1 org.opensearch.search.backpressure.SearchBackpressureIT.testSearchTaskCancellationWithHighCpu

• URL: https://build.ci.opensearch.org/job/gradle-check/17579/
• CommitID: ee815c6
  Please review all flaky tests that succeeded after retry and create an issue if one does not already exist to track the flaky failure.

[opensearch-trigger-bot]

The backport to 2.x failed:

The process '/usr/bin/git' failed with exit code 128

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-2.x 2.x
# Navigate to the new working tree
pushd ../.worktrees/backport-2.x
# Create a new branch
git switch --create backport/backport-8038-to-2.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 cb4361c00107e113c82f87103307c3626583e940
# Push it to GitHub
git push --set-upstream origin backport/backport-8038-to-2.x
# Go back to the original working tree
popd
# Delete the working tree
git worktree remove ../.worktrees/backport-2.x

Then, create a pull request where the base branch is 2.x and the compare/head branch is backport/backport-8038-to-2.x.