CollectorSampler (Collector: Core Library 2.18.2 API)

java.lang.Object
- zipkin2.collector.CollectorSampler

```
public abstract class CollectorSampler
extends java.lang.Object
```
CollectorSampler decides if a particular trace should be "sampled", i.e. recorded in permanent storage. This involves a consistent decision based on the span's trace ID with one notable exception: Debug spans are always stored.
Implementation

Accepts a percentage of trace ids by comparing their absolute value against a potentially dynamic boundary. eg isSampled == abs(traceId) <= boundary
While idempotent, this implementation's sample rate won't exactly match the input rate because trace ids are not perfectly distributed across 64bits. For example, tests have shown an error rate of 3% when 100K trace ids are random.

Field Summary

Fields
Modifier and Type Field Description

static CollectorSampler ALWAYS_SAMPLE

Constructor Summary

Constructors
Modifier Constructor Description

protected CollectorSampler()

Method Summary

All Methods Static Methods Instance Methods Abstract Methods Concrete Methods
Modifier and Type	Method	Description
`protected abstract long`	`boundary()`
`static CollectorSampler`	`create(float rate)`
`boolean`	`isSampled(java.lang.String hexTraceId, boolean debug)`	Returns true if spans with this trace ID should be recorded to storage.
`java.lang.String`	`toString()`

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

- Field Detail
  - ALWAYS_SAMPLE
```
public static final CollectorSampler ALWAYS_SAMPLE
```
- Constructor Detail
  - CollectorSampler
```
protected CollectorSampler()
```
- Method Detail
  - create
```
public static CollectorSampler create(float rate)
```
    Parameters:
    
    rate - minimum sample rate is 0.0001, or 0.01% of traces
  - boundary
```
protected abstract long boundary()
```
  - isSampled
```
public boolean isSampled(java.lang.String hexTraceId,
                         boolean debug)
```
    Returns true if spans with this trace ID should be recorded to storage.
    Zipkin v1 allows storage-layer sampling, which can help prevent spikes in traffic from overloading the system. Debug spans are always stored.
    This uses only the lower 64 bits of the trace ID as instrumentation still send mixed trace ID width.
    
    Parameters:
    
    hexTraceId - the lower 64 bits of the span's trace ID are checked against the boundary
    
    debug - when true, always passes sampling
  - toString
```
public java.lang.String toString()
```
    Overrides:
    
    toString in class java.lang.Object