Using Otel 1.26.0, getting Failed to connect to localhost/127.0.0.1:4317 error

[itsmaneesh]

I have been using Opentelemetry-javaagent:1.10.0 with the following env variables and auto-instrumentation was working fine and no error in the app logs or issue in exporting the spans. (Note, I have NOT configured the env var for metrics exporter i.e.: OTEL_METRICS_EXPORTER)

JAVA_TOOL_OPTIONS:                                                          -javaagent:/app/libs/opentelemetry-javaagent-1.10.0.jar
OTEL_EXPORTER_JAEGER_ENDPOINT:                                              http://jaeger.cluster.local:14250
OTEL_TRACES_EXPORTER:                                                       jaeger

But, I was trying to use Opentelemetry-java-agent:1.26.0 with the following env variables and auto-instrumentation works fine however there is continuous error in app logs in exporting metrics. (Note, I have NOT configured the env var for metrics exporter i.e.: OTEL_METRICS_EXPORTER)

JAVA_TOOL_OPTIONS:                                                          -javaagent:/app/libs/opentelemetry-javaagent-1.26.0.jar
OTEL_EXPORTER_JAEGER_ENDPOINT:                                              http://jaeger.cluster.local:14250
OTEL_TRACES_EXPORTER:                                                       jaeger

Error in app logs:

[otel.javaagent 2023-06-13 18:34:27:440 +0000] [OkHttp http://localhost:4317/...] ERROR io.opentelemetry.exporter.internal.grpc.OkHttpGrpcExporter - Failed to export metrics. The request could not be executed. Full error message: Failed to connect to localhost/127.0.0.1:4317

Question is:

1. Why do I see the error in case of Opentelemetry-javaagent:1.26.0 and not in with Opentelemetry-javaagent:1.10.0 ? Was this due to the env var OTEL_METRICS_EXPORTER defaulted to none earlier in version 1.10.0 of javaagent and now its defaulted otlp (change introduced in 1.13.0)? If so, what was the rationale to do so?

Ref: https://github.com/open-telemetry/opentelemetry-java/pull/4355/files#diff-77389189e1151331dcf90859f30c3ffc8f9fef10b73c600e84db953446e878ff

2. If my metrics export is prometheus then can I configure the below env var to resolve this issue?

• OTEL_METRICS_EXPORTER=prometheus
• OTEL_EXPORTER_PROMETHEUS_PORT=<prometheus_port>
• OTEL_EXPORTER_PROMETHEUS_HOST=<prometheus_host_name>

Thanks

[trask]

1. Why do I see the error in case of Opentelemetry-javaagent:1.26.0 and not in with Opentelemetry-javaagent:1.10.0 ? Was this due to the env var OTEL_METRICS_EXPORTER defaulted to none earlier in version 1.10.0 of javaagent and now its defaulted otlp (change introduced in 1.13.0)? If so, what was the rationale to do so?

yes

If so, what was the rationale to do so?

metrics were enabled by default once they became stable

2. If my metrics export is prometheus then can I configure the below env var to resolve this issue?

check out https://github.com/open-telemetry/opentelemetry-java/blob/main/sdk-extensions/autoconfigure/README.md#prometheus-exporter