serverless quarkus opentelemetry support

[hamburml]

Hello,

we use quarkus for serverless apps. With OpenTelemetry we monitor the application and also send metrics. The guide mentions quarkus.otel.simple=true to disable batching.

It works but sometimes we miss metrics and I am not sure why. I checked https://github.com/quarkusio/quarkus/blob/main/extensions/opentelemetry/runtime/src/main/java/io/quarkus/opentelemetry/runtime/exporter/otlp/sender/VertxHttpSender.java#L129C25-L129C37 and the usage of CompletionStage looks suspicious to me. I also do not find the usage of quarkus.otel.simple in that class.

Any advice?
@brunobat I saw some PRs concerning Otel from you so I thought I could ping you :)

[hamburml]

I did some more debugging.

I found out that there is an initial delay to send metrics. https://github.com/open-telemetry/opentelemetry-java/blob/release/v1.44.x/sdk/metrics/src/main/java/io/opentelemetry/sdk/metrics/export/PeriodicMetricReaderBuilder.java#L25

I also found out that quarkus uses an interval and when that time is gone all metrics are send out via otel.

What I want is: Send the Otel metric directly when i created it with

counter.add(1,
                Attributes.of(
                        AttributeKey.stringKey("timestamp"), DATE_TIME_FORMATTER.format(ZonedDateTime.now())));

Is that possible? It would be also okay if I could directly after this call a method from the MetricsExporter to export all metrics.

https://github.com/open-telemetry/opentelemetry-java/blob/release/v1.44.x/sdk/metrics/src/main/java/io/opentelemetry/sdk/metrics/export/PeriodicMetricReader.java#L84

Can I get the Instance of the MetricReader in quarkus? forceFlush is public and should do exactly what I want.

[brunobat]

@hamburml your findings make sense to me. Let me think about the implications.

[brunobat]

Created this issue from this discussion: #50826