Specify sampler probability using annotations or programmatically using Spring Cloud Sleuth?

We’re using Spring Boot 2.7.0, Spring cloud 2021.0.3 in GCP and have added these dependencies:

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-sleuth</artifactId>
</dependency>
<dependency>
    <groupId>com.google.cloud</groupId>
    <artifactId>spring-cloud-gcp-starter-trace</artifactId>
</dependency>
<dependency>
    <groupId>com.google.cloud</groupId>
    <artifactId>spring-cloud-gcp-starter-logging</artifactId>
</dependency>

We have specified the generic sample probability in our properties file like this:

spring.sleuth.sampler.probability=0.1
spring.sleuth.web.skipPattern=(^/admin/.*|.+favicon.*|^/ping$)

But for some methods we’d like to use a different sampler probability (e.g. we always want to generate a trace for some methods).

Questions:

1. Is it possible to specify the sample rate probability of a method when using annotations from the Spring Sleuth (or related) projects?
2. If not, is it possible to specify the sample rate probability of a method programmatically (without annotations)?
3. If not, is it possible to configure different sample rates in the spring property file / yaml file?

>Solution :

You can create a bean of type org.springframework.cloud.sleuth.exporter.SpanFilter. There you have access to FinishedSpan basing on which you can return true if you want to export the span or not.