Change abstraction point for transport protocol

[andrross]

The previous implementation had a transport switch point in InboundPipeline when the bytes were initially pulled off the wire. There was no implementation for any other protocol as the canHandleBytes method was hardcoded to return true. I believe this is the wrong point to switch on the protocol. This change makes NativeInboundBytesHandler protocol agnostic beyond the header. With this change, a complete message is parsed from the stream of bytes, with the header schema being unchanged from what exists today. The protocol switch point will now be at InboundHandler::inboundMessage. The header will indicate what protocol was used to serialize the the non-header bytes of the message and then invoke the appropriate handler based on that field.

Check List

• Functionality includes testing.
• API changes companion pull request created, if applicable.
• Public documentation issue/PR created, if applicable.

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[andrross]

@reta It was easier to illustrate the change here as a PR as opposed to describing it in an issue. The key changes here are basically:

• Remove protocol-specific types from NativeInboundBytesHandler (this class is now mis-named, but I didn't rename yet it to avoid polluting the diff).
• Make ProtocolInboundMessage an abstract class containing the non-protocol-specific parts of the message. Essentially only the StreamInput part is in NativeInboundMessage now.

The upshot of the change here is that the "header" part of the transport protocol remains unchanged, but they payload of each message is what now can be different protocols. The server will be able to freely exchange a mix of protocols on one connection at runtime (required for bwc anyway). The following code is where we will switch to the appropriate payload handler based on the protocol specified in the header:

OpenSearch/server/src/main/java/org/opensearch/transport/InboundHandler.java

Lines 110 to 122 in 0138b6e

	void inboundMessage(TcpChannel channel, ProtocolInboundMessage message) throws Exception {
	final long startTime = threadPool.relativeTimeInMillis();
	channel.getChannelStats().markAccessed(startTime);
	messageReceivedFromPipeline(channel, message, startTime);
	}
	private void messageReceivedFromPipeline(TcpChannel channel, ProtocolInboundMessage message, long startTime) throws IOException {
	ProtocolMessageHandler protocolMessageHandler = protocolMessageHandlers.get(message.getTransportProtocol());
	if (protocolMessageHandler == null) {
	throw new IllegalStateException("No protocol message handler found for protocol: " + message.getTransportProtocol());
	}
	protocolMessageHandler.messageReceived(channel, message, startTime, slowLogThresholdMs, messageListener);
	}

[github-actions]

❌ Gradle check result for 0138b6e: FAILURE

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?

[dblock]

This looks right to me!

[reta]

This looks right to me!

Double it!

[github-actions]

❕ Gradle check result for d4217c1: UNSTABLE

• TEST FAILURES:

      1 org.opensearch.cluster.MinimumClusterManagerNodesIT.testThreeNodesNoClusterManagerBlock

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

Attention: Patch coverage is 84.09091% with 21 lines in your changes missing coverage. Please review.

Project coverage is 71.88%. Comparing base (f5da8c8) to head (f6d5ce9).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
.../org/opensearch/transport/InboundBytesHandler.java	88.40%	0 Missing and 8 partials ⚠️
.../java/org/opensearch/transport/InboundMessage.java	84.61%	4 Missing and 2 partials ⚠️
...transport/nativeprotocol/NativeInboundMessage.java	0.00%	3 Missing ⚠️
...in/java/org/opensearch/transport/TcpTransport.java	0.00%	2 Missing ⚠️
.../java/org/opensearch/transport/InboundHandler.java	50.00%	1 Missing ⚠️
...va/org/opensearch/transport/TransportProtocol.java	80.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main   #15432      +/-   ##
============================================
+ Coverage     71.79%   71.88%   +0.09%     
- Complexity    63263    63305      +42     
============================================
  Files          5231     5233       +2     
  Lines        296526   296526              
  Branches      42832    42827       -5     
============================================
+ Hits         212900   213171     +271     
+ Misses        66121    65782     -339     
- Partials      17505    17573      +68     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[github-actions]

❌ Gradle check result for 95eeaf0: FAILURE

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 result for 4c6b24f: FAILURE

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 result for 39c14fd: SUCCESS

[github-actions]

✅ Gradle check result for c3c7a27: SUCCESS

[github-actions]

❌ Gradle check result for 27a7a59: FAILURE

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 result for 8580ace: UNSTABLE

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 result for f6d5ce9: FAILURE

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 result for f6d5ce9: SUCCESS

[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:

# Navigate to the root of your repository
cd $(git rev-parse --show-toplevel)
# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add ../.worktrees/OpenSearch/backport-2.x 2.x
# Navigate to the new working tree
pushd ../.worktrees/OpenSearch/backport-2.x
# Create a new branch
git switch --create backport/backport-15432-to-2.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 5663b4ae5c5553b358226f15f17b89aa843f9479
# Push it to GitHub
git push --set-upstream origin backport/backport-15432-to-2.x
# Go back to the original working tree
popd
# Delete the working tree
git worktree remove ../.worktrees/OpenSearch/backport-2.x

Then, create a pull request where the base branch is 2.x and the compare/head branch is backport/backport-15432-to-2.x.

[dblock]

@andrross backport manually pls?