Class DeclarativeSampler<M>
- java.lang.Object
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- brave.sampler.DeclarativeSampler<M>
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- Type Parameters:
M
- The type that uniquely identifies this method, specifically for tracing. Most often a trace annotation, but could also be aMethod
or another declarative reference such asjavax.ws.rs.container.ResourceInfo
.
- All Implemented Interfaces:
SamplerFunction<M>
public abstract class DeclarativeSampler<M> extends Object implements SamplerFunction<M>
This is an implementation of how to decide whether to trace a request using annotations on a java method. It is not an implementation of aspect-oriented or otherwise declarative tracing. See the test cases for this class for example implementations.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.
- Since:
- 4.4
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Nested Class Summary
Nested Classes Modifier and Type Class Description static interface
DeclarativeSampler.ProbabilityOfMethod<M>
static interface
DeclarativeSampler.RateForMethod<M>
Deprecated.since 5.8, useDeclarativeSampler.ProbabilityOfMethod
static interface
DeclarativeSampler.RateOfMethod<M>
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Deprecated Methods Modifier and Type Method Description static <M> DeclarativeSampler<M>
create(DeclarativeSampler.RateForMethod<M> rateForMethod)
Deprecated.since 5.8, usecreateWithProbability(ProbabilityOfMethod)
static <M> DeclarativeSampler<M>
createWithProbability(DeclarativeSampler.ProbabilityOfMethod<M> probabilityOfMethod)
static <M> DeclarativeSampler<M>
createWithRate(DeclarativeSampler.RateOfMethod<M> rateOfMethod)
SamplingFlags
sample(M method)
Deprecated.Since 5.8, usetrySample(Object)
Sampler
toSampler(M method)
Deprecated.Since 5.8, useTracer.startScopedSpan(String, SamplerFunction, Object)
Sampler
toSampler(M method, Sampler fallback)
Deprecated.Since 5.8, useTracer.startScopedSpan(String, SamplerFunction, Object)
Boolean
trySample(M method)
Returns an overriding sampling decision for a new trace.
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Method Detail
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createWithProbability
public static <M> DeclarativeSampler<M> createWithProbability(DeclarativeSampler.ProbabilityOfMethod<M> probabilityOfMethod)
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createWithRate
public static <M> DeclarativeSampler<M> createWithRate(DeclarativeSampler.RateOfMethod<M> rateOfMethod)
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trySample
@Nullable public Boolean trySample(@Nullable M method)
Returns an overriding sampling decision for a new trace. Returning null is typically used to defer to thetrace ID sampler
.- Specified by:
trySample
in interfaceSamplerFunction<M>
- Parameters:
method
- parameter to evaluate for a sampling decision. null input results in a null result- Returns:
- true to sample a new trace or false to deny. Null defers the decision.
- Since:
- 5.8
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create
public static <M> DeclarativeSampler<M> create(DeclarativeSampler.RateForMethod<M> rateForMethod)
Deprecated.since 5.8, usecreateWithProbability(ProbabilityOfMethod)
- Since:
- 4.4
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toSampler
@Deprecated public Sampler toSampler(M method)
Deprecated.Since 5.8, useTracer.startScopedSpan(String, SamplerFunction, Object)
- Since:
- 4.4
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toSampler
@Deprecated public Sampler toSampler(M method, Sampler fallback)
Deprecated.Since 5.8, useTracer.startScopedSpan(String, SamplerFunction, Object)
- Since:
- 4.19
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sample
@Deprecated public SamplingFlags sample(@Nullable M method)
Deprecated.Since 5.8, usetrySample(Object)
- Since:
- 4.4
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