All Known Implementing Classes:

InMemoryCollectorMetrics
```
public interface CollectorMetrics
```
Instrumented applications report spans over a transport such as Kafka. Zipkin collectors receive these messages, decoding them into spans, apply sampling, and queues them for storage.
Callbacks on this type are invoked by zipkin collectors to improve the visibility of the system. A typical implementation will report metrics to a telemetry system for analysis and reporting.
Spans Collected vs Queryable Spans

A span queried may be comprised of multiple spans collected. While instrumentation should report complete spans, Instrumentation often patch the same span twice, ex adding annotations. Also, RPC spans include at least 2 messages due to the client and the server reporting separately. Finally, some storage components merge patches at ingest. For these reasons, you should be cautious to alert on queryable spans vs stored spans, unless you control the instrumentation in such a way that queryable spans/message is reliable.
Key Relationships

The following relationships can be used to consider health of the tracing system.
```
 
 Successful Messages = Accepted messages -
 Dropped messages. Alert when this is less than amount of
 messages sent from instrumentation.
 Stored spans <= Accepted spans - Dropped spans. Alert when this drops below the
 collection-tier sample rate.
 
 
 
```

Field Summary

Fields
Modifier and Type Field Description

static CollectorMetrics NOOP_METRICS

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method	Description
`CollectorMetrics`	`forTransport(java.lang.String transportType)`	Those who wish to partition metrics by transport can call this method to include the transport type in the backend metric key.
`void`	`incrementBytes(int quantity)`	Increments the number of bytes containing serialized spans in a message.
`void`	`incrementMessages()`	Increments count of messages received, which contain 0 or more spans.
`void`	`incrementMessagesDropped()`	Increments count of messages that could not be read.
`void`	`incrementSpans(int quantity)`	Increments the count of spans read from a successful message.
`void`	`incrementSpansDropped(int quantity)`	Increments the count of spans dropped for any reason.

- Field Detail
  - NOOP_METRICS
```
static final CollectorMetrics NOOP_METRICS
```
- Method Detail
  - forTransport
```
CollectorMetrics forTransport(java.lang.String transportType)
```
    Those who wish to partition metrics by transport can call this method to include the transport type in the backend metric key.
    For example, an implementation may by default report incremented spans to the key "zipkin.collector.span.accepted". When metrics.forTransport("kafka" is called, the counter would report to "zipkin.collector.kafka.span.accepted"
    
    Parameters:
    
    transportType - ex "http", "rabbitmq", "kafka"
  - incrementMessages
```
void incrementMessages()
```
    Increments count of messages received, which contain 0 or more spans. Ex POST requests or Kafka messages consumed.
  - incrementMessagesDropped
```
void incrementMessagesDropped()
```
    Increments count of messages that could not be read. Ex malformed content, or peer disconnect.
  - incrementSpans
```
void incrementSpans(int quantity)
```
    Increments the count of spans read from a successful message. When bundling is used, accepted spans will be a larger number than successful messages.
  - incrementBytes
```
void incrementBytes(int quantity)
```
    Increments the number of bytes containing serialized spans in a message.
    Note: this count should relate to the raw data structures, like json or thrift, and discount compression, enveloping, etc.
  - incrementSpansDropped
```
void incrementSpansDropped(int quantity)
```
    Increments the count of spans dropped for any reason. For example, failure queueing to storage or sampling decisions.

Interface CollectorMetrics

Spans Collected vs Queryable Spans

Key Relationships

Field Summary

Method Summary

Field Detail

NOOP_METRICS

Method Detail

forTransport

incrementMessages

incrementMessagesDropped

incrementSpans

incrementBytes

incrementSpansDropped