AbstractMetricsContext (Apache Hadoop Main 2.7.4 API)

java.lang.Object
- org.apache.hadoop.metrics.spi.AbstractMetricsContext

All Implemented Interfaces:

org.apache.hadoop.metrics.MetricsContext

Direct Known Subclasses:

CompositeContext, GangliaContext, NoEmitMetricsContext, NullContext, NullContextWithUpdateThread
```
@InterfaceAudience.Public
 @InterfaceStability.Evolving
public abstract class AbstractMetricsContext
extends Object
implements org.apache.hadoop.metrics.MetricsContext
```
The main class of the Service Provider Interface. This class should be extended in order to integrate the Metrics API with a specific metrics client library.
This class implements the internal table of metric data, and the timer on which data is to be sent to the metrics system. Subclasses must override the abstract emitRecord method in order to transmit the data.

Field Summary
- Fields inherited from interface org.apache.hadoop.metrics.MetricsContext
  DEFAULT_PERIOD

Constructor Summary

Constructors
Modifier Constructor and Description

protected AbstractMetricsContext()
Creates a new instance of AbstractMetricsContext

Constructors
Modifier	Constructor and Description
`protected`	`AbstractMetricsContext()` Creates a new instance of AbstractMetricsContext

Method Summary

All Methods Instance Methods Abstract Methods Concrete Methods
Modifier and Type	Method and Description
`void`	`close()` Stops monitoring and frees buffered data, returning this object to its initial state.
`org.apache.hadoop.metrics.MetricsRecord`	`createRecord(String recordName)` Creates a new AbstractMetricsRecord instance with the given `recordName`.
`protected abstract void`	`emitRecord(String contextName, String recordName, OutputRecord outRec)` Sends a record to the metrics system.
`protected void`	`flush()` Called each period after all records have been emitted, this method does nothing.
`Map<String,Collection<OutputRecord>>`	`getAllRecords()` Retrieves all the records managed by this MetricsContext.
`protected String`	`getAttribute(String attributeName)` Convenience method for subclasses to access factory attributes.
`protected Map<String,String>`	`getAttributeTable(String tableName)` Returns an attribute-value map derived from the factory attributes by finding all factory attributes that begin with contextName.tableName.
`org.apache.hadoop.metrics.ContextFactory`	`getContextFactory()` Returns the factory by which this context was created.
`String`	`getContextName()` Returns the context name.
`int`	`getPeriod()` Returns the timer period.
`void`	`init(String contextName, org.apache.hadoop.metrics.ContextFactory factory)` Initializes the context.
`boolean`	`isMonitoring()` Returns true if monitoring is currently in progress.
`protected org.apache.hadoop.metrics.MetricsRecord`	`newRecord(String recordName)` Subclasses should override this if they subclass MetricsRecordImpl.
`protected void`	`parseAndSetPeriod(String attributeName)` If a period is set in the attribute passed in, override the default with it.
`void`	`registerUpdater(org.apache.hadoop.metrics.Updater updater)` Registers a callback to be called at time intervals determined by the configuration.
`protected void`	`remove(MetricsRecordImpl record)` Called by MetricsRecordImpl.remove().
`protected void`	`setPeriod(int period)` Sets the timer period
`void`	`startMonitoring()` Starts or restarts monitoring, the emitting of metrics records.
`void`	`stopMonitoring()` Stops monitoring.
`void`	`unregisterUpdater(org.apache.hadoop.metrics.Updater updater)` Removes a callback, if it exists.
`protected void`	`update(MetricsRecordImpl record)` Called by MetricsRecordImpl.update().

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

- Constructor Detail
  - AbstractMetricsContext
```
protected AbstractMetricsContext()
```
    Creates a new instance of AbstractMetricsContext
- Method Detail
  - init
```
public void init(String contextName,
                 org.apache.hadoop.metrics.ContextFactory factory)
```
    Initializes the context.
    
    Specified by:
    
    init in interface org.apache.hadoop.metrics.MetricsContext
    
    Parameters:
    
    contextName - The given name for this context
    
    factory - The creator of this context
  - getAttribute
```
protected String getAttribute(String attributeName)
```
    Convenience method for subclasses to access factory attributes.
  - getAttributeTable
```
protected Map<String,String> getAttributeTable(String tableName)
```
    Returns an attribute-value map derived from the factory attributes by finding all factory attributes that begin with contextName.tableName. The returned map consists of those attributes with the contextName and tableName stripped off.
  - getContextName
```
public String getContextName()
```
    Returns the context name.
    
    Specified by:
    
    getContextName in interface org.apache.hadoop.metrics.MetricsContext
    
    Returns:
    
    the context name
  - getContextFactory
```
public org.apache.hadoop.metrics.ContextFactory getContextFactory()
```
    Returns the factory by which this context was created.
  - startMonitoring
```
public void startMonitoring()
                     throws IOException
```
    Starts or restarts monitoring, the emitting of metrics records.
    
    Specified by:
    
    startMonitoring in interface org.apache.hadoop.metrics.MetricsContext
    
    Throws:
    
    IOException
  - stopMonitoring
```
public void stopMonitoring()
```
    Stops monitoring. This does not free buffered data.
    
    Specified by:
    
    stopMonitoring in interface org.apache.hadoop.metrics.MetricsContext
    
    See Also:
    
    close()
  - isMonitoring
```
public boolean isMonitoring()
```
    Returns true if monitoring is currently in progress.
    
    Specified by:
    
    isMonitoring in interface org.apache.hadoop.metrics.MetricsContext
  - close
```
public void close()
```
    Stops monitoring and frees buffered data, returning this object to its initial state.
    
    Specified by:
    
    close in interface org.apache.hadoop.metrics.MetricsContext
  - createRecord
```
public final org.apache.hadoop.metrics.MetricsRecord createRecord(String recordName)
```
    Creates a new AbstractMetricsRecord instance with the given recordName. Throws an exception if the metrics implementation is configured with a fixed set of record names and recordName is not in that set.
    
    Specified by:
    
    createRecord in interface org.apache.hadoop.metrics.MetricsContext
    
    Parameters:
    
    recordName - the name of the record
    
    Throws:
    
    org.apache.hadoop.metrics.MetricsException - if recordName conflicts with configuration data
  - newRecord
```
protected org.apache.hadoop.metrics.MetricsRecord newRecord(String recordName)
```
    Subclasses should override this if they subclass MetricsRecordImpl.
    
    Parameters:
    
    recordName - the name of the record
    
    Returns:
    
    newly created instance of MetricsRecordImpl or subclass
  - registerUpdater
```
public void registerUpdater(org.apache.hadoop.metrics.Updater updater)
```
    Registers a callback to be called at time intervals determined by the configuration.
    
    Specified by:
    
    registerUpdater in interface org.apache.hadoop.metrics.MetricsContext
    
    Parameters:
    
    updater - object to be run periodically; it should update some metrics records
  - unregisterUpdater
```
public void unregisterUpdater(org.apache.hadoop.metrics.Updater updater)
```
    Removes a callback, if it exists.
    
    Specified by:
    
    unregisterUpdater in interface org.apache.hadoop.metrics.MetricsContext
    
    Parameters:
    
    updater - object to be removed from the callback list
  - getAllRecords
```
public Map<String,Collection<OutputRecord>> getAllRecords()
```
    Retrieves all the records managed by this MetricsContext. Useful for monitoring systems that are polling-based.
    
    Specified by:
    
    getAllRecords in interface org.apache.hadoop.metrics.MetricsContext
    
    Returns:
    
    A non-null collection of all monitoring records.
  - emitRecord
```
protected abstract void emitRecord(String contextName,
                                   String recordName,
                                   OutputRecord outRec)
                            throws IOException
```
    Sends a record to the metrics system.
    
    Throws:
    
    IOException
  - flush
```
protected void flush()
              throws IOException
```
    Called each period after all records have been emitted, this method does nothing. Subclasses may override it in order to perform some kind of flush.
    
    Throws:
    
    IOException
  - update
```
protected void update(MetricsRecordImpl record)
```
    Called by MetricsRecordImpl.update(). Creates or updates a row in the internal table of metric data.
  - remove
```
protected void remove(MetricsRecordImpl record)
```
    Called by MetricsRecordImpl.remove(). Removes all matching rows in the internal table of metric data. A row matches if it has the same tag names and values as record, but it may also have additional tags.
  - getPeriod
```
public int getPeriod()
```
    Returns the timer period.
    
    Specified by:
    
    getPeriod in interface org.apache.hadoop.metrics.MetricsContext
  - setPeriod
```
protected void setPeriod(int period)
```
    Sets the timer period
  - parseAndSetPeriod
```
protected void parseAndSetPeriod(String attributeName)
```
    If a period is set in the attribute passed in, override the default with it.

Class AbstractMetricsContext

Field Summary

Fields inherited from interface org.apache.hadoop.metrics.MetricsContext

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

AbstractMetricsContext

Method Detail

init

getAttribute

getAttributeTable

getContextName

getContextFactory

startMonitoring

stopMonitoring

isMonitoring

close

createRecord

newRecord

registerUpdater

unregisterUpdater

getAllRecords

emitRecord

flush

update

remove

getPeriod

setPeriod

parseAndSetPeriod