[ISSUE #6339]🚀Add producer batch send examples

[mxsm]

Which Issue(s) This PR Fixes(Closes)

• Fixes [Feature🚀] Add producer send to queue examples #6339

Brief Description

How Did You Test This Change?

Summary by CodeRabbit

• New Features
  • Added a new example demonstrating how to send messages to specific RocketMQ queues. The example showcases five different sending patterns: direct send, send with timeout, send with callback, send with callback and timeout, and one-way send. This provides practical guidance for queue-specific message publishing scenarios.

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Walkthrough

Adds a new RocketMQ producer example demonstrating queue-specific message sending. The example showcases five sending patterns: direct send, send with timeout, send with callback, send with callback and timeout, and one-way send. Updates the Cargo.toml manifest to register the new example.

Changes

Cohort / File(s)	Summary
Example Registration rocketmq-example/Cargo.toml	Added [[example]] entry registering "producer-send-to-queue" example pointing to the new send_to_queue.rs file.
Queue Sending Example rocketmq-example/examples/producer/send_to_queue.rs	New example file demonstrating five queue-specific message sending methods via DefaultMQProducer: basic send, send with timeout, send with callback, send with callback and timeout, and one-way send. Includes producer initialization, queue selection, and proper shutdown.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Poem

🐰 A queue of messages, neat and grand,
Five ways to send them, hand in hand,
With callbacks waiting, timeouts set,
A producer's path, we won't forget! 🚀

🚥 Pre-merge checks | ✅ 5 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Title check	⚠️ Warning	Title mentions 'batch send examples' but changes add only 'send to queue' examples. The title does not accurately reflect the actual implementation.	Update PR title to '[ISSUE #6339] Add producer send to queue examples' to match the actual changes made.

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Linked Issues check	✅ Passed	The linked issue #6339 requests examples for producer send to queue functionality, and the PR implements exactly that with five send-to-queue methods.
Out of Scope Changes check	✅ Passed	All changes are directly related to the linked issue objective: a new producer send-to-queue example file and corresponding Cargo.toml entry. No unrelated changes detected.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
Merge Conflict Detection	✅ Passed	✅ No merge conflicts detected when merging into main

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch feat-6339

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No actionable comments were generated in the recent review. 🎉

🧹 Recent nitpick comments

rocketmq-example/examples/producer/send_to_queue.rs (3)

32-36: Constants don't need pub visibility in an example binary.

Since this is a standalone example binary (not a library), the pub qualifier on these constants is unnecessary. Plain const would suffice.

♻️ Suggested diff

-pub const PRODUCER_GROUP: &str = "producer_send_to_queue";
-pub const DEFAULT_NAMESRVADDR: &str = "127.0.0.1:9876";
-pub const TOPIC: &str = "SendToQueueTestTopic";
-pub const TAG: &str = "QueueTag";
-pub const TIMEOUT_MS: u64 = 3000;
+const PRODUCER_GROUP: &str = "producer_send_to_queue";
+const DEFAULT_NAMESRVADDR: &str = "127.0.0.1:9876";
+const TOPIC: &str = "SendToQueueTestTopic";
+const TAG: &str = "QueueTag";
+const TIMEOUT_MS: u64 = 3000;

---

140-154: Duplicate callback closures across send_to_queue_with_callback and send_to_queue_with_callback_timeout.

The callback closure on lines 144–148 is identical to lines 177–181. For an example file, inline duplication can be acceptable for readability, but extracting a small helper would reduce copy-paste drift if the example evolves.

♻️ Suggested approach

Define a reusable callback function at the bottom of the file:

fn on_send_complete(result: Option<&SendResult>, error: Option<&dyn std::error::Error>) {
    match (result, error) {
        (Some(r), None) => println!("   Callback: Success - {:?}", r),
        (None, Some(e)) => println!("   Callback: Error - {}", e),
        _ => println!("   Callback: Unknown state"),
    }
}

Then pass on_send_complete in place of the inline closure in both call sites.

Also applies to: 173-188

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1-1: Copyright year says 2023 for a file created in 2026.

Very minor nit — the header reads Copyright 2023 but this is a brand-new file. Consider updating to 2026 (or confirming this is the project's standard boilerplate).

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[rocketmq-rust-bot]

LGTM - All CI checks passed ✅