Metrics (Java Driver for Scylla and Apache Cassandra

java.lang.Object
- com.datastax.driver.core.Metrics

```
public class Metrics
extends Object
```
Metrics exposed by the driver.
The metrics exposed by this class use the Metrics library and you should refer its documentation for details on how to handle the exposed metric objects.
By default, metrics are exposed through JMX, which is very useful for development and browsing, but for production environments you may want to have a look at the reporters provided by the Metrics library which could be more efficient/adapted.

Nested Class Summary

Nested Classes
Modifier and Type Class and Description

class Metrics.Errors
Metrics on errors encountered.

Nested Classes
Modifier and Type	Class and Description
`class`	`Metrics.Errors` Metrics on errors encountered.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`com.codahale.metrics.Gauge<Integer>`	`getBlockingExecutorQueueDepth()` Returns the number of queued up tasks in the `blocking executor`.
`com.codahale.metrics.Meter`	`getBytesReceived()` Returns the number of bytes received so far.
`com.codahale.metrics.Meter`	`getBytesSent()` Returns the number of bytes sent so far.
`com.codahale.metrics.Gauge<Integer>`	`getConnectedToHosts()` Returns the number of Cassandra hosts the driver is currently connected to (that is have at least one connection opened to).
`Metrics.Errors`	`getErrorMetrics()` Returns an object grouping metrics related to the errors encountered.
`com.codahale.metrics.Gauge<Integer>`	`getExecutorQueueDepth()` Returns the number of queued up tasks in the `main internal executor`.
`com.codahale.metrics.Gauge<Integer>`	`getInFlightRequests()` Returns the total number of in flight requests to Cassandra hosts.
`com.codahale.metrics.Gauge<Integer>`	`getKnownHosts()` Returns the number of Cassandra hosts currently known by the driver (that is whether they are currently considered up or down).
`com.codahale.metrics.Gauge<Integer>`	`getOpenConnections()` Returns the total number of currently opened connections to Cassandra hosts.
`com.codahale.metrics.Gauge<Integer>`	`getReconnectionSchedulerQueueSize()` Returns the number of queued up tasks in the `reconnection executor`.
`com.codahale.metrics.MetricRegistry`	`getRegistry()` Returns the registry containing all metrics.
`com.codahale.metrics.Gauge<Integer>`	`getRequestQueueDepth()` Returns the total number of enqueued requests on all Cassandra hosts.
`com.codahale.metrics.Timer`	`getRequestsTimer()` Returns metrics on the user requests performed on the Cluster.
`com.codahale.metrics.Gauge<Map<Host,Integer>>`	`getShardAwarenessInfo()`
`com.codahale.metrics.Gauge<Integer>`	`getTaskSchedulerQueueSize()` Returns the number of queued up tasks in the `scheduled tasks executor`.
`com.codahale.metrics.Gauge<Integer>`	`getTrashedConnections()` Returns the total number of currently "trashed" connections to Cassandra hosts.

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

- Method Detail
  - getRegistry
```
public com.codahale.metrics.MetricRegistry getRegistry()
```
    Returns the registry containing all metrics.
    The metrics registry allows you to easily use the reporters that ship with Metrics or a custom written one.
    For instance, if metrics is this object, you could export the metrics to csv files using:
```
     com.codahale.metrics.CsvReporter.forRegistry(metrics.getRegistry()).build(new File("measurements/")).start(1, TimeUnit.SECONDS);
 
```
    If you already have a MetricRegistry in your application and wish to add the driver's metrics to it, the recommended approach is to use a listener:
```
     // Your existing registry:
     final com.codahale.metrics.MetricRegistry myRegistry = ...

     cluster.getMetrics().getRegistry().addListener(new com.codahale.metrics.MetricRegistryListener() {
         @Override
         public void onGaugeAdded(String name, Gauge<?> gauge) {
             if (myRegistry.getNames().contains(name)) {
                 // name is already taken, maybe prefix with a namespace
                 ...
             } else {
                 myRegistry.register(name, gauge);
             }
         }

         ... // Implement other methods in a similar fashion
     });
 
```
    Since reporting is handled by your registry, you'll probably also want to disable JMX reporting with Cluster.Builder.withoutJMXReporting().
    Returns:
    
    the registry containing all metrics.
  - getRequestsTimer
```
public com.codahale.metrics.Timer getRequestsTimer()
```
    Returns metrics on the user requests performed on the Cluster.
    This metric exposes
    - the total number of requests.
    - the requests rate (in requests per seconds), including 1, 5 and 15 minute rates.
    - the mean, min and max latencies, as well as latency at a given percentile.
    Returns:
    
    a Timer metric object exposing the rate and latency for user requests.
  - getErrorMetrics
```
public Metrics.Errors getErrorMetrics()
```
    Returns an object grouping metrics related to the errors encountered.
    
    Returns:
    
    an object grouping metrics related to the errors encountered.
  - getKnownHosts
```
public com.codahale.metrics.Gauge<Integer> getKnownHosts()
```
    Returns the number of Cassandra hosts currently known by the driver (that is whether they are currently considered up or down).
    
    Returns:
    
    the number of Cassandra hosts currently known by the driver.
  - getConnectedToHosts
```
public com.codahale.metrics.Gauge<Integer> getConnectedToHosts()
```
    Returns the number of Cassandra hosts the driver is currently connected to (that is have at least one connection opened to).
    
    Returns:
    
    the number of Cassandra hosts the driver is currently connected to.
  - getOpenConnections
```
public com.codahale.metrics.Gauge<Integer> getOpenConnections()
```
    Returns the total number of currently opened connections to Cassandra hosts.
    
    Returns:
    
    The total number of currently opened connections to Cassandra hosts.
  - getTrashedConnections
```
public com.codahale.metrics.Gauge<Integer> getTrashedConnections()
```
    Returns the total number of currently "trashed" connections to Cassandra hosts.
    When the load to a host decreases, the driver will reclaim some connections in order to save resources. No requests are sent to these connections anymore, but they are kept open for an additional amount of time (PoolingOptions.getIdleTimeoutSeconds()), in case the load goes up again. This metric counts connections in that state.
    
    Returns:
    
    The total number of currently trashed connections to Cassandra hosts.
  - getInFlightRequests
```
public com.codahale.metrics.Gauge<Integer> getInFlightRequests()
```
    Returns the total number of in flight requests to Cassandra hosts.
    
    Returns:
    
    The total number of in flight requests to Cassandra hosts.
  - getRequestQueueDepth
```
public com.codahale.metrics.Gauge<Integer> getRequestQueueDepth()
```
    Returns the total number of enqueued requests on all Cassandra hosts.
    
    Returns:
    
    The total number of enqueued requests on all Cassandra hosts.
    
    See Also:
    
    Session.State#getRequestQueueDepth(Host)
  - getExecutorQueueDepth
```
public com.codahale.metrics.Gauge<Integer> getExecutorQueueDepth()
```
    Returns the number of queued up tasks in the main internal executor.
    If the executor's task queue is not accessible – which happens when the executor is not an instance of ThreadPoolExecutor – then this gauge returns -1.
    
    Returns:
    
    The number of queued up tasks in the main internal executor, or -1, if that number is unknown.
  - getBlockingExecutorQueueDepth
```
public com.codahale.metrics.Gauge<Integer> getBlockingExecutorQueueDepth()
```
    Returns the number of queued up tasks in the blocking executor.
    If the executor's task queue is not accessible – which happens when the executor is not an instance of ThreadPoolExecutor – then this gauge returns -1.
    
    Returns:
    
    The number of queued up tasks in the blocking executor, or -1, if that number is unknown.
  - getReconnectionSchedulerQueueSize
```
public com.codahale.metrics.Gauge<Integer> getReconnectionSchedulerQueueSize()
```
    Returns the number of queued up tasks in the reconnection executor.
    A queue size > 0 does not necessarily indicate a backlog as some tasks may not have been scheduled to execute yet.
    If the executor's task queue is not accessible – which happens when the executor is not an instance of ThreadPoolExecutor – then this gauge returns -1.
    
    Returns:
    
    The size of the work queue for the reconnection executor, or -1, if that number is unknown.
  - getTaskSchedulerQueueSize
```
public com.codahale.metrics.Gauge<Integer> getTaskSchedulerQueueSize()
```
    Returns the number of queued up tasks in the scheduled tasks executor.
    A queue size > 0 does not necessarily indicate a backlog as some tasks may not have been scheduled to execute yet.
    If the executor's task queue is not accessible – which happens when the executor is not an instance of ThreadPoolExecutor – then this gauge returns -1.
    
    Returns:
    
    The size of the work queue for the scheduled tasks executor, or -1, if that number is unknown.
  - getShardAwarenessInfo
```
public com.codahale.metrics.Gauge<Map<Host,Integer>> getShardAwarenessInfo()
```
  - getBytesSent
```
public com.codahale.metrics.Meter getBytesSent()
```
    Returns the number of bytes sent so far.
    Note that this measures unencrypted traffic, even if SSL is enabled (the probe is inserted before SSL handlers in the Netty pipeline). In practice, SSL overhead should be negligible after the initial handshake.
    
    Returns:
    
    the number of bytes sent so far.
  - getBytesReceived
```
public com.codahale.metrics.Meter getBytesReceived()
```
    Returns the number of bytes received so far.
    Note that this measures unencrypted traffic, even if SSL is enabled (the probe is inserted before SSL handlers in the Netty pipeline). In practice, SSL overhead should be negligible after the initial handshake.
    
    Returns:
    
    the number of bytes received so far.

Class Metrics

Nested Class Summary

Method Summary

Methods inherited from class java.lang.Object

Method Detail

getRegistry

getRequestsTimer

getErrorMetrics

getKnownHosts

getConnectedToHosts

getOpenConnections

getTrashedConnections

getInFlightRequests

getRequestQueueDepth

getExecutorQueueDepth

getBlockingExecutorQueueDepth

getReconnectionSchedulerQueueSize

getTaskSchedulerQueueSize

getShardAwarenessInfo

getBytesSent

getBytesReceived