fix: script leak and shut down and remove per-message goroutine

[hpsing]

• safe drain
• remove per message goroutine (fan-out in subscribe)
• fix error/cancel in publish/subsribe worker

Summary by CodeRabbit

• Bug Fixes

  • Corrected several command-line error messages for clearer feedback.

• Improvements

  • Added stricter input validation with clearer failures for publish/subscribe options.
  • Improved error aggregation so worker failures stop the run and surface consistently.
  • Enhanced file-output behavior to ensure orderly flushing and a final "all data flushed" notice.
  • Simplified and made message reception more reliable.

• Documentation

  • Updated usage examples and Docker Compose port guidance for multi-node runs; added notes on index ranges and a new data-size option.

[coderabbitai]

📝 Walkthrough

Walkthrough

Refactors CLI clients to centralize per-worker error aggregation and cancellation, simplifies subscribe receive loops, validates input flags, and updates file-writing to a cancellable writer with header and filename parameters. No public API additions.

Changes

Cohort / File(s)	Summary
Multi-publish grpc_p2p_client/cmd/multi-publish/main.go	Added input validation, derived randomByteLen, per-worker error channel (errCh) and context cancellation on worker error; moved header/writer init to top-level; changed sendMessages to return nil on ctx cancel and localize data buffer.
Multi-subscribe grpc_p2p_client/cmd/multi-subscribe/main.go	Fixed flag help text, added errCh to aggregate worker errors and cancel on failure; receiveMessages now returns an error and reads stream.Recv() directly; removed internal msg channel/goroutine and simplified logging and shutdown sequence.
Single command grpc_p2p_client/cmd/single/main.go	Replaced goroutine+channel+select receive pattern with direct stream.Recv() loop and inline HandleResponse; fixed flag help text formatting.
Shared utilities grpc_p2p_client/shared/utils.go	ReadIPsFromFile validates non-empty filename; WriteToFile signature changed to accept filename and header, is context-aware (select over ctx.Done/dataCh), drains remaining data on shutdown, and signals completion via done.
Docs docs/guide.md, readme.md	Documentation and examples updated for multi-node Docker port mappings, new flags (-datasize), and index-range usage in examples.

Sequence Diagram(s)

mermaid
sequenceDiagram
participant Main
participant Worker
participant ErrCollector
participant FileWriter
participant Context
Main->>Worker: spawn worker (publish/subscribe)
Worker->>ErrCollector: send error (if any)
ErrCollector->>Main: notify error
Main->>Context: cancel()
Main->>FileWriter: close / stop writer (signal done)
FileWriter-->>Main: flush complete / done

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

• fix: refactor grpc_p2p_client to resolve multiple main() conflict #57: Modifies the same cmd/* clients and shared/utils.go file-writing and IP-reading logic; strongly related to the write/ReadIPs refactor in this PR.

Suggested reviewers

• paiva

Poem

🐇 I hopped through streams and channel lanes,

Collected errors, calmed the strains,
Writers hush when contexts cry,
Messages now pass in a simpler sigh,
Code hops light beneath spring rains.

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title directly addresses the main changes: removing per-message goroutines and fixing error/cancellation handling in publish/subscribe workers, which aligns with the changeset's core refactoring efforts.

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✨ Finishing touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch singh/minor-fixe

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[coderabbitai]

Actionable comments posted: 1

🤖 Fix all issues with AI agents

In `@grpc_p2p_client/shared/utils.go`:
- Around line 246-250: Move the error check so you verify the result of
writer.WriteString(data + "\n") before calling writer.Flush(), and also handle
the error returned by writer.Flush(); specifically, after calling
writer.WriteString in the current function (where writer.WriteString and
writer.Flush are used) check if err != nil and log/return immediately, then call
writer.Flush() and check its error too (log/return if non-nil). Reference the
existing symbols writer.WriteString and writer.Flush to locate the code to
change.

🧹 Nitpick comments (1)

grpc_p2p_client/shared/utils.go (1)

247-247: Consider batching flushes for better performance.

Calling Flush() after every write negates the benefits of buffered I/O. For high-throughput scenarios, this could be a performance bottleneck. Consider flushing periodically (e.g., every N writes or on a timer) or relying on the deferred Flush() at function exit.

[swarna1101]

LGTM!