Package com.mapr.org.apache.hadoop.metrics

Class ContextFactory

  • @LimitedPrivate({"HDFS","MapReduce"})
@Evolving
public class ContextFactory
extends java.lang.Object
    Factory class for creating MetricsContext objects. To obtain an instance of this class, use the static getFactory() method.

    • Constructor Summary

      Constructors 
      Modifier Constructor Description
      protected ContextFactory()
      Creates a new instance of ContextFactory

    • Method Summary

      All Methods Static Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      java.util.Collection<MetricsContext> getAllContexts()
      Returns all MetricsContexts built by this factory.
      java.lang.Object getAttribute​(java.lang.String attributeName)
      Returns the value of the named attribute, or null if there is no attribute of that name.
      java.lang.String[] getAttributeNames()
      Returns the names of all the factory's attributes.
      MetricsContext getContext​(java.lang.String contextName)  
      MetricsContext getContext​(java.lang.String refName, java.lang.String contextName)
      Returns the named MetricsContext instance, constructing it if necessary using the factory's current configuration attributes.
      static ContextFactory getFactory()
      Returns the singleton ContextFactory instance, constructing it if necessary.
      static MetricsContext getNullContext​(java.lang.String contextName)
      Returns a "null" context - one which does nothing.
      void removeAttribute​(java.lang.String attributeName)
      Removes the named attribute if it exists.
      void setAttribute​(java.lang.String attributeName, java.lang.Object value)
      Sets the named factory attribute to the specified value, creating it if it did not already exist.

      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

    • Constructor Detail

      • ContextFactory

        protected ContextFactory()
        Creates a new instance of ContextFactory

    • Method Detail

      • getAttribute

        public java.lang.Object getAttribute​(java.lang.String attributeName)
        Returns the value of the named attribute, or null if there is no attribute of that name.
        Parameters:
        attributeName - the attribute name
        Returns:
        the attribute value

      • getAttributeNames

        public java.lang.String[] getAttributeNames()
        Returns the names of all the factory's attributes.
        Returns:
        the attribute names

      • setAttribute

        public void setAttribute​(java.lang.String attributeName,
                         java.lang.Object value)
        Sets the named factory attribute to the specified value, creating it if it did not already exist. If the value is null, this is the same as calling removeAttribute.
        Parameters:
        attributeName - the attribute name
        value - the new attribute value

      • removeAttribute

        public void removeAttribute​(java.lang.String attributeName)
        Removes the named attribute if it exists.
        Parameters:
        attributeName - the attribute name

      • getContext

        public MetricsContext getContext​(java.lang.String refName,
                                 java.lang.String contextName)
                          throws java.io.IOException,
                                 java.lang.ClassNotFoundException,
                                 java.lang.InstantiationException,
                                 java.lang.IllegalAccessException
        Returns the named MetricsContext instance, constructing it if necessary using the factory's current configuration attributes.

        When constructing the instance, if the factory property contextName.class exists, its value is taken to be the name of the class to instantiate. Otherwise, the default is to create an instance of org.apache.hadoop.metrics.spi.NullContext, which is a dummy "no-op" context which will cause all metric data to be discarded.

        Parameters:
        contextName - the name of the context
        Returns:
        the named MetricsContext
        Throws:
        java.io.IOException
        java.lang.ClassNotFoundException
        java.lang.InstantiationException
        java.lang.IllegalAccessException

      • getContext

        public MetricsContext getContext​(java.lang.String contextName)
                          throws java.io.IOException,
                                 java.lang.ClassNotFoundException,
                                 java.lang.InstantiationException,
                                 java.lang.IllegalAccessException
        Throws:
        java.io.IOException
        java.lang.ClassNotFoundException
        java.lang.InstantiationException
        java.lang.IllegalAccessException

      • getAllContexts

        public java.util.Collection<MetricsContext> getAllContexts()
        Returns all MetricsContexts built by this factory.

      • getNullContext

        public static MetricsContext getNullContext​(java.lang.String contextName)
        Returns a "null" context - one which does nothing.

      • getFactory

        public static ContextFactory getFactory()
                                 throws java.io.IOException
        Returns the singleton ContextFactory instance, constructing it if necessary.

        When the instance is constructed, this method checks if the file hadoop-metrics.properties exists on the class path. If it exists, it must be in the format defined by java.util.Properties, and all the properties in the file are set as attributes on the newly created ContextFactory instance.

        Returns:
        the singleton ContextFactory instance
        Throws:
        java.io.IOException