fix: [Geneva uploader] Optimize upload path by using Bytes to eliminate unnecessary clones (specifically for retry scenario)

[lalitb]

Changes

Replaces Vec<u8> with bytes::Bytes for compressed telemetry data to eliminate expensive memory clones in the upload path, especially critical for retry scenarios.

Problem

The upload_batch() method was cloning the entire compressed payload (potentially MBs) on every upload attempt:

// Before: client.rs:141
self.uploader.upload(batch.data.clone(), ...) //  Vec::clone() copies entire 1+ MB buffer

Impact for a 1 MB batch with 3 retry attempts:

• 3 MB of unnecessary heap allocations (one per retry)
• ~300 µs wasted on memcpy operations

Solution

Changed EncodedBatch.data from Vec to bytes::Bytes:

  // After: client.rs:141
  self.uploader.upload(batch.data.clone(), ...) // Bytes::clone() is O(1) refcount increment

How it works:

1. Bytes::from(Vec<u8>) does NOT copy - it takes ownership of the Vec's allocation and wraps it in a reference-counted container (zero-copy conversion)
2. Bytes::clone() just increments an atomic refcount - no data is copied
3. Both original and cloned Bytes point to the same underlying buffer

Why Bytes instead of Arc?

While Arc<Vec<u8>> would also provide cheap cloning, Bytes is the better choice for our HTTP upload use case:

1. Native reqwest integration: reqwest::Body has impl From<Bytes> that wraps the buffer directly without copying (used at uploader.rs:242). With Arc, we'd need to pass .as_ref() (giving &[u8]), which causes reqwest to allocate internally when converting to Body.
2. Industry standard for async I/O: Bytes is the standard type for byte buffers in Rust's async ecosystem (tokio, hyper, reqwest), ensuring optimal integration.
3. Future optimizations: Bytes::slice() provides zero-copy views into the buffer, which could be useful for - Optimizing Bond encoding pipeline (bond_encoder.rs, central_blob.rs) if we identify unnecessary intermediate copies during schema/event serialization.

Merge requirement checklist

• CONTRIBUTING guidelines followed
• Unit tests added/updated (if applicable)
• Appropriate CHANGELOG.md files updated for non-trivial, user-facing changes
• Changes in public API reviewed (if applicable)

[codecov]

Codecov Report

❌ Patch coverage is 75.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 53.9%. Comparing base (1ee6a9c) to head (7c510f9).

Files with missing lines	Patch %	Lines
...eneva/geneva-uploader/src/ingestion_service/mod.rs	0.0%	1 Missing ⚠️

Additional details and impacted files

@@          Coverage Diff          @@
##            main    #470   +/-   ##
=====================================
  Coverage   53.9%   53.9%           
=====================================
  Files         71      71           
  Lines      11220   11220           
=====================================
  Hits        6057    6057           
  Misses      5163    5163           

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[Copilot]

Pull Request Overview

This PR optimizes the Geneva uploader's upload path by replacing Vec<u8> with bytes::Bytes for compressed telemetry data to eliminate expensive memory clones during retry scenarios.

• Changes EncodedBatch.data field from Vec<u8> to bytes::Bytes for zero-copy cloning
• Updates all related function signatures and test code to use Bytes
• Adds bytes dependency to enable reference-counted buffer sharing

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
Cargo.toml	Adds bytes = "1.5" dependency
client.rs	Updates EncodedBatch.data field type and adds bytes import
otlp_encoder.rs	Converts Vec<u8> to Bytes in batch creation and adds import
uploader.rs	Updates upload method parameter from Vec<u8> to Bytes
mod.rs	Updates test structures to use Bytes instead of Vec<u8>

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