I am building microservices using Spring Boot for building microservices and Kubernetes for implementing the microservices patterns. In this regards, I am looking for alternate for Spring cloud sleuth. What options do I have to replace Sleuth for distributed tracing. The idea here is to inject the timestamp, trace and span outside of the spring boot application as a sidecar container.
Echoing the previous answer suggesting Jaeger. You should also look at the OpenTelemetry Java instrumentation. The cloud sleuth API is also supported by the Java instrumentation in OpenTemeletry. The auto instrumentation will work outside of the application code, but it still needs to run inside the JVM. There is no way to do distributed tracing without instrumenting the code, hence a sidecar doesn't work for generating span data.