com.datastax.oss.driver.api.core.metrics

Interface Metrics

public interface Metrics

A wrapper around a MetricRegistry to expose the driver's metrics.

This type exists mainly to avoid a hard dependency to Dropwizard Metrics (that is, the JAR can be completely removed from the classpath if metrics are disabled). It also provides convenience methods to access individual metrics programmatically.

Method Summary

Modifier and Type	Method and Description
default <T extends com.codahale.metrics.Metric> Optional<T>	getNodeMetric(Node node, NodeMetric metric) Shortcut for getNodeMetric(node, metric, null).
<T extends com.codahale.metrics.Metric> Optional<T>	getNodeMetric(Node node, NodeMetric metric, String profileName) Retrieves a node-level metric for a given node from the registry.
com.codahale.metrics.MetricRegistry	getRegistry() Returns the underlying Dropwizard registry.
default <T extends com.codahale.metrics.Metric> Optional<T>	getSessionMetric(SessionMetric metric) Shortcut for getSessionMetric(metric, null).
<T extends com.codahale.metrics.Metric> Optional<T>	getSessionMetric(SessionMetric metric, String profileName) Retrieves a session-level metric from the registry.

Method Detail

getRegistry

@NonNull
com.codahale.metrics.MetricRegistry getRegistry()

Returns the underlying Dropwizard registry.

Typically, this can be used to configure a reporter.

See Also:

Reporters (Dropwizard Metrics manual)

getSessionMetric

@NonNull
<T extends com.codahale.metrics.Metric> Optional<T> getSessionMetric(@NonNull
                                                                              SessionMetric metric,
                                                                              @Nullable
                                                                              String profileName)

Retrieves a session-level metric from the registry.

To determine the type of each metric, refer to the comments in the default reference.conf (included in the driver's codebase and JAR file). Note that the method does not check that this type is correct (there is no way to do this at runtime because some metrics are generic); if you use the wrong type, you will get a ClassCastException in your code:

 // Correct:
 Gauge<Integer> connectedNodes = getSessionMetric(DefaultSessionMetric.CONNECTED_NODES);

 // Wrong, will throw CCE:
 Counter connectedNodes = getSessionMetric(DefaultSessionMetric.CONNECTED_NODES);
 

Parameters:

profileName - the name of the execution profile, or null if the metric is not associated to any profile. Note that this is only included for future extensibility: at this time, the driver does not break up metrics per profile. Therefore you can always use getSessionMetric(SessionMetric) instead of this method.

Returns:

the metric, or empty if it is disabled.

getSessionMetric

@NonNull
default <T extends com.codahale.metrics.Metric> Optional<T> getSessionMetric(@NonNull
                                                                                      SessionMetric metric)

Shortcut for getSessionMetric(metric, null).

getNodeMetric

@NonNull
<T extends com.codahale.metrics.Metric> Optional<T> getNodeMetric(@NonNull
                                                                           Node node,
                                                                           @NonNull
                                                                           NodeMetric metric,
                                                                           @Nullable
                                                                           String profileName)

Retrieves a node-level metric for a given node from the registry.

To determine the type of each metric, refer to the comments in the default reference.conf (included in the driver's codebase and JAR file). Note that the method does not check that this type is correct (there is no way to do this at runtime because some metrics are generic); if you use the wrong type, you will get a ClassCastException in your code:

 // Correct:
 Gauge<Integer> openConnections = getNodeMetric(node, DefaultNodeMetric.OPEN_CONNECTIONS);

 // Wrong, will throw CCE:
 Counter openConnections = getNodeMetric(node, DefaultNodeMetric.OPEN_CONNECTIONS);
 

Parameters:

profileName - the name of the execution profile, or null if the metric is not associated to any profile. Note that this is only included for future extensibility: at this time, the driver does not break up metrics per profile. Therefore you can always use getNodeMetric(Node, NodeMetric) instead of this method.

Returns:

the metric, or empty if it is disabled.

getNodeMetric

@NonNull
default <T extends com.codahale.metrics.Metric> Optional<T> getNodeMetric(@NonNull
                                                                                   Node node,
                                                                                   @NonNull
                                                                                   NodeMetric metric)

Shortcut for getNodeMetric(node, metric, null).