M
- The type that uniquely identifies this method, specifically for tracing. Most often a
trace annotation, but could also be a Method
or another declarative
reference such as javax.ws.rs.container.ResourceInfo
.public final class DeclarativeSampler<M> extends Object
Example: A user defines an annotation, for example com.myco.Traced
, and a lookup
function for its rate (could be simple as reading a field, or even a constant). An interceptor
uses this sampler on each invocation of a potentially annotated target. The result decides
whether a new trace should be started or not.
No runtime parameters are considered here, but that doesn't mean you can't achieve
parameterized sampling using this. If your method is annotated such that it only accepts a
fraction of requests, adding a custom @Traced
annotation would apply to that subset. For
example, if you have a JAX-RS method, it is already qualified by method and likely path. A user
can add and inspect their own grouping annotation to override whatever the default rate is.
Under the scenes, a map of samplers by method is maintained. The size of this map should not be a problem when it directly relates to declared methods. For example, this would be invalid if annotations were created at runtime and didn't match.
Modifier and Type | Class | Description |
---|---|---|
static interface |
DeclarativeSampler.RateForMethod<M> |
Modifier and Type | Method | Description |
---|---|---|
static <M> DeclarativeSampler<M> |
create(DeclarativeSampler.RateForMethod<M> rateForMethod) |
|
SamplingFlags |
sample(M method) |
public static <M> DeclarativeSampler<M> create(DeclarativeSampler.RateForMethod<M> rateForMethod)
public SamplingFlags sample(@Nullable M method)
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