Agent limits metric name length to 63

[tomilchik]

Description OTEL Agent 1.28.0 applies rule "metric name not to exceed 63 characters" and drops metrics (does not push them to Collector) that break this rule.

Steps to reproduce Build a Java web app that uses Spring Security 6.*. Attach OTEL Agent v1.24.0+. Call app's http endpoint (any) to trigger execution of Spring Security filter chain.

What did you expect to see? No WARN logs from OTEL Agent re: length of metric names

What did you see instead? Observed: WARN entries in app log similar to this: [otel.javaagent ] WARN io.opentelemetry.sdk.metrics.internal.InstrumentNameValidator - Instrument name "spring.security.filterchain.WebAsyncManagerIntegrationFilter.after" is invalid, returning noop instrument. Instrument names must consist of 63 or fewer characters including alphanumeric, _, -, -, and start with a letter"

What version and what artifacts are you using? Artifacts:

• io.opentelemetry.javaagent:opentelemetry.javaagent:jar:1.28.0. Metrics exporter: otlp
• org.springframework.boot:spring-boot-starter-security:jar:3.0.5 (pulls transitive Spring Security 6.0.2 dependencies)

How did you reference these artifacts? (excerpt from your build.gradle, pom.xml, etc) As dependency in pom.xml

Environment Compiler: java 17.0.6 2023-01-17 LTS OS: RHEL 8.8 Runtime (if different from JDK above): same as compiler OS (if different from OS compiled on): same

Additional context After inet searches - the number 63 looks to come from OTEL spec: https://opentelemetry.io/docs/specs/otel/metrics/api/ So - this might be considered "a feature, not a bug". If that is the case: please count my vote for increasing this number in the OTEL implementation (against the spec); the number is 1)arbitrary, and 2)too low. Non-OTEL metric collection implementations (e.g. metrics scraped from Spring Boot actuator/prometheus and delivered to a Prometheus instance with Grafana UI on top) do not seem to have this limitation, at least not at 63.

[trask]

see https://github.com/open-telemetry/opentelemetry-specification/issues/3422

we are hoping to get this restriction lifted

[tomilchik]

That's a good news! Any estimates on when/version?

[trask]

sorry, no

[jkwatson]

closing this, as it's not an issue we can address without a spec change.