grpc/grpc-java

Cardinality of grpc_target attribute for grpc.client.* metrics is too large

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#12322 opened on Aug 28, 2025

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enhancementhelp wanted

Description

What version of gRPC-Java are you using?

1.71.0

What is your environment?

OS: Linux JDK: 21

What did you expect to see?

No warnings when enabling default OpenTelemetry metrics.

What did you see instead?

WARNING: Instrument grpc.client.attempt.started has exceeded the maximum allowed cardinality (1999).
WARNING: Instrument grpc.client.attempt.rcvd_total_compressed_message_size has exceeded the maximum allowed cardinality (1999).
WARNING: Instrument grpc.client.attempt.sent_total_compressed_message_size has exceeded the maximum allowed cardinality (1999).
WARNING: Instrument grpc.client.call.duration has exceeded the maximum allowed cardinality (1999).
WARNING: Instrument grpc.client.attempt.duration has exceeded the maximum allowed cardinality (1999).

This is caused by the grpc_target attribute having a very large cardinality.

I see that this attribute is listed for these metrics at https://github.com/grpc/proposal/blob/master/A66-otel-stats.md. However, for very large deployments this can be problematic. Is there a way to turn this attribute off?

Steps to reproduce the bug

Have a client which connects to 2000+ servers (either at once or over time).

Contributor guide

Tech stack
javaopentelemetry
Domain
backendobservability
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
gRPC Java basicsOpenTelemetry instrumentationJava programming
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
40
Research direction
Examine the gRPC Java implementation of OpenTelemetry metrics, specifically the grpc target attribute in client metrics. Look for where the attribute is set (likely in the client call instrumentation) and consider adding a configuration option to disable it. Review the proposal A66 otel stats.md for context on the attribute's purpose. Also check if there are existing configuration flags for cardinality control in the gRPC Java codebase.