support for customizing the tracing sampler on a per-task basis.

{
    "task-name": {
        "active": bool
    }
}

a task is basically the "span name" based on the work being performed.
a task can be an API endpoint interaction, a gorm query, etc. see: https://opentelemetry.io/docs/specs/otel/trace/api/#span

if a task is not represented in the configuration file then the task will be treated normally, with tracing enabled.

consider the following example configuration files:

Example 1

this will enable all tracing.

{}

Example 2

this will enable all tracing except for the /health endpoint.

{
    "/health": {
        "active": false
    }
}

Example 3

{
    "/health": {
        "active": false
    },
    "/api/v1/deployments/:org/:repo": {
        "active": false
    },
    "/api/v1/:worker": {
        "active": true
    },
    "gorm.query": {
        "active": false
    }
}

/health with active: false will disable tracing on /health.

/api/v1/deployments/:org/:repo with active: false will disable tracing on /api/v1/deployments/:org/:repo for ALL :org and :repo parameters.

/api/v1/:worker with active: true will do nothing at this point, because any tasks that are not present in the configuration file will automatically be sampled normally.
for now this is slightly confusing, but in the future there will be more configuration fields that will determine how an active: true task is sampled.

gorm.query with active: false would disable tracing for raw gorm queries. this is meant to show that the config applies to all trace tasks and not just API/HTTP endpoints.

all other tasks will be sampled as normal using the parent rate limit sampler! this includes all api endpoints and gorm queries.

Potential Enhancements

planning future enhancements like per-task ratio-sampling and per-endpoint method restrictions.

consider the following stretch goal configuration file:

{
    "/health": {
        "active": false
    },
    "/api/v1/deployments/:org/:repo": {
        "active": true,
        "ratio": 0.3, // record only 30% 
        "methods": [ "get", "put" ], // record particular methods
        "query_parameters": [ "event=push" ] // record particular queries
    },