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Introduce load-balanced channel for OpenTelemetry exporters#2175

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dkostyrev wants to merge 1 commit intoTraceMachina:mainfrom
joomcode:feature/balanced-channel
Open

Introduce load-balanced channel for OpenTelemetry exporters#2175
dkostyrev wants to merge 1 commit intoTraceMachina:mainfrom
joomcode:feature/balanced-channel

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@dkostyrev dkostyrev commented Feb 23, 2026 •
edited by MarcusSorealheis
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Summary

This PR introduces client-side load balancing for OpenTelemetry (OTLP) gRPC connections using the ginepro library. When the NL_OTEL_ENDPOINT (name to be discussed, maybe boolean flag?) environment variable is set, NativeLink will create a load-balanced channel for exporting logs, traces, and metrics, distributing requests across multiple backend endpoints resolved via DNS. This change allows to distribute OTLP traffic across multiple OTLP collector instances.

Changes

Load-balanced OTLP exports:

  • Added ginepro dependency to provide client-side load balancing for gRPC channels used by OpenTelemetry exporters
  • Introduced NL_OTEL_ENDPOINT environment variable to configure the OTLP endpoint for load-balanced connections
  • Changed init_tracing() from synchronous to async to support balanced channel initialization
  • Updated OpenTelemetry dependencies from v0.29 to v0.30 to support the new channel configuration
  • All three exporters (logs, traces, metrics) now share the same load-balanced channel when configured

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@dkostyrev dkostyrev force-pushed the feature/balanced-channel branch from eb9bfe9 to b86f6d1 Compare February 23, 2026 16:21
@dkostyrev dkostyrev force-pushed the feature/balanced-channel branch from b86f6d1 to 9533feb Compare February 23, 2026 16:27
@dkostyrev dkostyrev force-pushed the feature/balanced-channel branch from 9533feb to 6406230 Compare February 23, 2026 16:35
@MarcusSorealheis MarcusSorealheis requested a review from palfrey March 5, 2026 15:28
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MarcusSorealheis commented Mar 5, 2026

@dkostyrev Than you for this awesome PR. I have finally had a bit of time to explore it and now I understand quite a bit.

This is fantastic.

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MarcusSorealheis commented Mar 5, 2026

@amankrx when you get a chance, please help with the merge conflict here.

MarcusSorealheis
MarcusSorealheis approved these changes Mar 5, 2026
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src/bin/redis_store_tester.rs
.block_on(async {
// The OTLP exporters need to run in a Tokio context.
spawn!("init tracing", async { init_tracing() })
spawn!("init tracing", async { init_tracing().await })
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@MarcusSorealheis MarcusSorealheis Mar 5, 2026

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oof! Good catch.

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palfrey commented Mar 6, 2026

That coverage issue is interesting. mold: error: undefined symbol: __memcpy_chk is the sort of problem we used to be having before the fixes in #2192 that removes the hardeningDisable bit that was a workaround to this before. Not quite sure why this is hitting here now, but might need to re-add the workaround.

@dkostyrev dkostyrev force-pushed the feature/balanced-channel branch from 29cb3d7 to dff32cd Compare March 6, 2026 12:34
@dkostyrev dkostyrev force-pushed the feature/balanced-channel branch from 31d41d4 to 892ecee Compare March 16, 2026 13:48
@dkostyrev
Introduce load-balanced channel for OpenTelemetry exporters
1eb7f46 
Add client-side load balancing to OTLP gRPC connections using ginepro.
When NL_OTEL_ENDPOINT is set, the telemetry system creates a load-balanced
channel shared across log, trace, and metric exporters. This enables better
distribution of telemetry traffic across multiple OTLP collector instances
and improves overall system resilience.

- Add ginepro dependency for gRPC load balancing
- Upgrade OpenTelemetry dependencies from 0.29 to 0.30
- Change init_tracing() to async to support channel initialization
- Add NL_OTEL_ENDPOINT environment variable for configuration
- Update all OTLP exporters to use shared load-balanced channel
@dkostyrev dkostyrev force-pushed the feature/balanced-channel branch from 892ecee to 1eb7f46 Compare March 16, 2026 13:59
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MarcusSorealheis commented Mar 16, 2026

This is looking good.

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dkostyrev commented Mar 16, 2026

Thanks for the review, still trying to pass failed CI checks

@palfrey palfrey mentioned this pull request Mar 30, 2026
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palfrey commented Mar 30, 2026

I think this is actually hitting https://users.rust-lang.org/t/undefined-reference-to-memcpy-chk-with-target-x86-64-unknown-linux-musl/113567 as it's building a linked zstd, not the vendored one. Upstream has a PR that would sort this out, and I've just prodded them on that.

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@MarcusSorealheis MarcusSorealheis MarcusSorealheis approved these changes

@amankrx amankrx amankrx approved these changes

@palfrey palfrey Awaiting requested review from palfrey

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@dkostyrev @MarcusSorealheis @palfrey @amankrx