CAUSEWAY-3975: Open Telemetry Integration

[andi-huber]

• Proof of Concept (using micrometer API internally)
• Figure out how to configure (OTLP)
• Govern via ENV var whether to enable Observation
• Usage Guide (ADOC)

Task-Url: https://issues.apache.org/jira/browse/CAUSEWAY-3975

Proposal: make observation an opt-in choice based on profile observation being active, which allows to opt-in only for deployment scenarios where observation is desired

Minimal Setup (for Applications)

Maven

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-opentelemetry</artifactId>
</dependency>
<dependency>
    <groupId>io.micrometer</groupId>
    <artifactId>micrometer-registry-otlp</artifactId>
</dependency>

Config

spring:
  application:
    name: <name of service>
  
management:
  tracing:
    sampling:
      probability: 1  
  opentelemetry:
    tracing:
      export:
        otlp:
          endpoint: http://<my-endpoint>:4318/v1/traces

Spring

Disables metric export (we are currently only using traces).

@Bean
OtlpConfig otlpConfig() {
    return new OtlpConfig() {
        @Override public @Nullable String get(final String key) { return null;}
        @Override public boolean enabled() { return false; }
    };
}

Docker

One of many options is to use Jaeger as telemetry collector.

docker run -d --name jaeger \
-p 16686:16686 \
-p 4317:4317 \
-p 4318:4318 \
-p 5778:5778 \
-p 9411:9411 \
cr.jaegertracing.io/jaegertracing/jaeger

Then Jaeger's UI is at http://<my-endpoint>:16686.

[andi-huber]

I don't like that as the final answer, because we don't really know how to handle potential exceptions of the runnable.

[andi-huber]

why needed? if done wrong, could be registered too early for other configurations to have a chance