Sampler (Brave 5.17.0 API)

java.lang.Object
- brave.sampler.Sampler

Direct Known Subclasses:

BoundarySampler, CountingSampler, RateLimitingSampler
```
public abstract class Sampler
extends Object
```
Sampler is responsible for deciding if a particular trace should be "sampled", i.e. whether the overhead of tracing will occur and/or if a trace will be reported to the collection tier.
Zipkin v1 uses before-the-fact sampling. This means that the decision to keep or drop the trace is made before any work is measured, or annotations are added. As such, the input parameter to zipkin v1 samplers is the trace ID (lower 64-bits under the assumption all bits are random).
The instrumentation sampling decision happens once, at the root of the trace, and is propagated downstream. For this reason, the algorithm needn't be consistent based on trace ID.

Field Summary

Fields
Modifier and Type Field Description

static Sampler ALWAYS_SAMPLE

static Sampler NEVER_SAMPLE

Constructor Summary

Constructors
Constructor Description

Sampler()

Method Summary

All Methods Static Methods Instance Methods Abstract Methods Concrete Methods
Modifier and Type	Method	Description
`static Sampler`	`create(float probability)`	Returns a sampler, given a probability expressed as a percentage.
`abstract boolean`	`isSampled(long traceId)`	Returns true if the trace ID should be measured.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - ALWAYS_SAMPLE
```
public static final Sampler ALWAYS_SAMPLE
```
  - NEVER_SAMPLE
```
public static final Sampler NEVER_SAMPLE
```
- Constructor Detail
  - Sampler
```
public Sampler()
```
- Method Detail
  - isSampled
```
public abstract boolean isSampled(long traceId)
```
    Returns true if the trace ID should be measured.
    
    Parameters:
    
    traceId - The trace ID to be decided on, can be ignored
  - create
```
public static Sampler create(float probability)
```
    Returns a sampler, given a probability expressed as a percentage.
    The sampler returned is good for low volumes of traffic (<100K requests), as it is precise. If you have high volumes of traffic, consider BoundarySampler.
    
    Parameters:
    
    probability - probability a trace will be sampled. minimum is 0.01, or 1% of traces