grpc/grpc-java

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

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#12,322 opened on Aug 28, 2025

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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

Research direction
Investigate how to reduce the cardinality of the grpc target attribute, possibly by adding a configuration option to disable it or by using a different attribute like target name without port. Check the OpenTelemetry metrics specification and the gRPC Java codebase for existing mechanisms to control metric attributes.
Tech stack
java
Domain
backendapi
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
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
GitJavagRPC basics
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
60