feat(java): implement Async Connection Pooling using FixedChannelPool by rythm-sachdeva · Pull Request #2606 · apache/iggy

rythm-sachdeva · 2026-01-24T09:23:48Z

Description

Implements connection pooling for AsyncTcpConnection using Netty's FixedChannelPool to handle concurrent async operations efficiently.

Changes

Connection Pooling: Replaced single channel with FixedChannelPool for concurrent request handling
Pool Metrics: Added PoolMetrics class to track:
- Active connections
- Total requests and errors
- Wait times (min/max/average in nanoseconds, microseconds, and milliseconds)
- Error rate percentage
Configuration: Added TCPConnectionPoolConfig with builder pattern for customizing:
- Max connections (default: 5)
- Max pending acquires (default: 1000)
- Acquire timeout (default: 3000ms)
Request Correlation: Implemented FIFO queue-based request/response matching using ConcurrentLinkedQueue
Broadcast Operations: Added broadcastAsync() method to execute commands across all pooled connections (useful for authentication)
Client Integration: Exposed pool configuration via AsyncIggyTcpClient.Builder.connectionPoolSize()

Implementation Details

Uses Netty's FixedChannelPool with ChannelHealthChecker.ACTIVE
Each channel has its own IggyResponseHandler with a response queue
Pool automatically releases channels after request completion
Handles connection errors gracefully with proper cleanup

Testing

Added integration test testConnectionPoolMetrics() to verify metrics tracking
Existing async integration tests validate concurrent operations
Pool properly handles concurrent sends and polls

ex172000 · 2026-01-27T05:01:27Z

foreign/java/java-sdk/src/main/java/org/apache/iggy/client/async/tcp/AsyncIggyTcpClient.java

+                connectionPoolSize.orElse(5), // Default to 5 if not provided
+                1000, // maxPendingAcquires
+                connectionTimeout.map(Duration::toMillis).orElse(3000L) // map Duration to millis


Do we want to 1) make the params configurable? 2) or put them as static final constants?
Also seems we have the default provided by the builder already?

Yes

Yes

Yes

@rythm-sachdeva please address this comment. The numeric values should be declared as static final. If any value has a default in the builder, it should be aligned in both places. Also, please remove the inline comments, the code is self-explanatory.

ex172000 · 2026-01-27T05:04:59Z

foreign/java/java-sdk/src/main/java/org/apache/iggy/client/async/tcp/AsyncTcpConnection.java


    /**
-     * Connects to the server asynchronously.
+     * BroadCast Command to each connection


very minor nit: Broadcasts to keep it consistent :)

ex172000 · 2026-01-27T05:06:32Z

foreign/java/java-sdk/src/main/java/org/apache/iggy/client/async/tcp/AsyncTcpConnection.java

+            lastFuture.add(sendAsync(commandCode, payload.retainedDuplicate()));
+        }
+        // 2. Return the last Future (caller can treat this like a single request)
+        return lastFuture.get(lastFuture.size() - 1);


Not sure if I understand correctly, but how does the last future guarantee on the behavior of all futures?

Does not guarantee, I assumed that if last request is fulfilled the previous requests have been successful. Though not a good approach. If there is any better approach you suggest I am happy to take feedback and implement it in an optimal way.

ex172000 · 2026-01-27T05:15:53Z

foreign/java/java-sdk/src/main/java/org/apache/iggy/client/async/tcp/AsyncTcpConnection.java

+    // private final AtomicLong requestIdGenerator = new AtomicLong(0);
+    // private final ConcurrentHashMap<Long, CompletableFuture<ByteBuf>> pendingRequests = new ConcurrentHashMap<>();


Do we want to remove them?

If this code isn't being used, please remove it rather than leaving it commented out.

github-actions · 2026-02-04T00:34:55Z

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed in 7 days if no further activity occurs.

If you need a review, please ensure CI is green and the PR is rebased on the latest master. Don't hesitate to ping the maintainers - either @core on Discord or by mentioning them directly here on the PR.

Thank you for your contribution!

rythm-sachdeva · 2026-02-09T14:21:08Z

Hi @mmodzelewski Can you please review .

mmodzelewski · 2026-02-09T21:20:40Z

Hi @mmodzelewski Can you please review .

Hey @rythm-sachdeva, I will, but I need some time. I might not get round to it until the beginning of next week.

slbotbm · 2026-02-17T17:46:03Z

@rythm-sachdeva Please see why CI is failing and fix the errors.

mmodzelewski · 2026-02-17T18:17:26Z

@rythm-sachdeva Please see why CI is failing and fix the errors.

@rythm-sachdeva I've added a verification if all ByteBufs are properly released (not leaked) and it appears that the new code does not release all resources. See the logs, or run the tests locally, you'll see reports of the leaks in there.

fix(java-sdk):Added Missing PoolMetrics and linting issues fix(java):fixed connection error fix(java):Fixed Linting Issues fix(java):fixed builder issues fix(java):fixed ci issues fix(java): fixed memory leaks

ex172000 reviewed Jan 27, 2026

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mmodzelewski linked an issue Jan 27, 2026 that may be closed by this pull request

[Java SDK] Implement Connection Pooling for Async Client #2232

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github-actions bot added the stale Inactive issue or pull request label Feb 4, 2026

hubcio changed the title ~~feat(java): Implemented Async Connection Pooling using FixedChannelPool (#2232)~~ feat(java): implement Async Connection Pooling using FixedChannelPool Feb 4, 2026

github-actions bot removed the stale Inactive issue or pull request label Feb 5, 2026

rythm-sachdeva force-pushed the feature/async-connection-pool branch 2 times, most recently from 2cdb131 to 50e8a36 Compare February 7, 2026 06:56

rythm-sachdeva force-pushed the feature/async-connection-pool branch from 50e8a36 to ca4583f Compare February 17, 2026 15:08

rythm-sachdeva force-pushed the feature/async-connection-pool branch from ca4583f to 17832af Compare February 18, 2026 00:50

feat(java): Implemented Async Connection Pooling using FixedChannelPool

8a80d3d

fix(java-sdk):Added Missing PoolMetrics and linting issues fix(java):fixed connection error fix(java):Fixed Linting Issues fix(java):fixed builder issues fix(java):fixed ci issues fix(java): fixed memory leaks

rythm-sachdeva force-pushed the feature/async-connection-pool branch from 17832af to 8a80d3d Compare February 18, 2026 15:34

		// private final AtomicLong requestIdGenerator = new AtomicLong(0);
		// private final ConcurrentHashMap<Long, CompletableFuture<ByteBuf>> pendingRequests = new ConcurrentHashMap<>();

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rythm-sachdeva commented Jan 24, 2026

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github-actions bot commented Feb 4, 2026

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rythm-sachdeva commented Feb 9, 2026

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mmodzelewski commented Feb 9, 2026

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slbotbm commented Feb 17, 2026

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mmodzelewski commented Feb 17, 2026

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