Delete prometheus-client-bridge

[jack-berg]

Component(s)

prometheus-client-bridge

What happened?

The functionality is implemented in opentelemetry-java in https://github.com/open-telemetry/opentelemetry-java/pull/6015, which allows you to associate your own PrometheusRegistry with PrometheusHttpServer.

Component version

latest

Log output

No response

Additional context

No response

[jkwatson]

I'm not sure that PR is a full replacement. I'm using the PrometheusServlet to serve up prometheus data. That uses the default registry, and the bridge lets me just let the default registry collect OTel metrics. I don't see how that PR will replace that usage, but I might be missing something.

[jack-berg]

I'm using the PrometheusServlet to serve up prometheus data.

You should be able to do this via PrometheusHttpServerBuilder#setPrometheusRegistry(PrometheusRegistry.defaultRegistry), no? The code registers an OTEL implementation of MultiCollector with whatever prometheus registry you configure: https://github.com/open-telemetry/opentelemetry-java/pull/6015/files#diff-6c5e18c7125e4889e56b4ba2225ca3a3d36e61d4a19a44b2c7cb06a4c9f43af8R62

In doing so, I think you should be able to define your own handler which reads from all the collectors associated with the registry.

[jkwatson]

I'm using the PrometheusServlet to serve up prometheus data.

You should be able to do this via PrometheusHttpServerBuilder#setPrometheusRegistry(PrometheusRegistry.defaultRegistry), no? The code registers an OTEL implementation of MultiCollector with whatever prometheus registry you configure: https://github.com/open-telemetry/opentelemetry-java/pull/6015/files#diff-6c5e18c7125e4889e56b4ba2225ca3a3d36e61d4a19a44b2c7cb06a4c9f43af8R62

In doing so, I think you should be able to define your own handler which reads from all the collectors associated with the registry.

But, I'm not using a Prometheus Http server...I'm using the built-in tomcat from spring-boot, with the prometheus servlet serving up the metrics.

[jack-berg]

Ah I think if I understand correctly, you would need to use PrometheusMetricReader and register it with both SdkMeterProvider and PrometheusRegistry.defaultRegistry.

I was going to say that we would have to make the new PrometheusMetricReader class public, but it looks like that's already the case. So https://github.com/open-telemetry/opentelemetry-java/pull/6015 actually defines two MetricReader implementations:

• PrometheusMetricReader, which implements MultiCollector and doesn't do anything until you do something with it which calls MetricSnapshots collect()
• PrometheusHttpServer, which uses PrometheusMetricReader internally, starts up an HTTP server, and calls PrometheusMetricReader#collect() to serve up responses to metric requests

Side note - if we go with this approach, we'll need to be careful to document that most users will want PrometheusHttpServer, NOT PrometheusMetricReader.

[jkwatson]

Oh! 🤔 I'd be happy to try that out, once it's merged and released; if it works, then I'm 👍🏽 on this proposal.