OpenTelemetry should not fail on context reloads

[frommeyerc]

Describe the bug
When using the spring-autoconfiguration integration and restarting the spring context (e.g. user spring-dev-tools) the new context fails to start. the reason is that the open-tracing integration tries to create and register a new version of the opentracing sdk. As this is build as enforced singleton an exception is thrown.

Interestingly there is a method called #resetForTest() that actually nulls the static field holding the globalOpenTelemetry.

Steps to reproduce

• Add the spring autoconfiguration to a spring-boot project
• Configure the spring-dev-tools
• Start the server
• Change code to trigger a hot reload
• Observe issue.

What did you expect to see?
I expected the context to come up again without issue.

What did you see instead?
The context failing with a BeanInstatiationException

What version are you using?
1.4.1-alpha

Environment
Compiler: Eclipse Java 11
OS: "Ubuntu 20.04"

[jkwatson]

Interesting. I suspect that the spring integration shouldn't be setting the global at all.

[anuraaga]

I'm not too familiar with how the reload works but am reading this

https://docs.spring.io/spring-boot/docs/current/reference/html/using.html#using.devtools.restart.customizing-the-classload

It seems to imply that only projects open in the IDE are loaded in the restart classloader. Since we'd expect our library to be included as a build dependency jar, it should be in the base classloader. Any idea why the Otel configuration is restarted or an approach to prevent it?

[trask]

@frommeyerc can you provide a repro for this issue that we can use to investigate?

[frommeyerc]

I should be able to compile s.th. in a couple of days.

[frommeyerc]

I created a repository here: https://github.com/frommeyerc/otel-demo/tree/master/opentelemetry-refresh
The simple Spring-Boot application does nothing but exposing a hello world http endpoint. If started with

mvn spring-boot:run

from the command line it will start on port 8080. If you modify the code it will automatically try to reload the context and fail with an exception.

[iNikem]

Fixed by #4051