Package org.apache.geode.cache

Class EvictionAttributes

java.lang.Object
org.apache.geode.cache.EvictionAttributes
public abstract class EvictionAttributes extends Object

Attributes that describe how a Region's size is managed through an eviction controller. Eviction controllers are defined by an EvictionAlgorithm and a EvictionAction. Once a Region is created with an eviction controller, it can not be removed, however it can be changed through an EvictionAttributesMutator.

Since:
GemFire 5.0
See Also:

  • Field Details

    • DEFAULT_ENTRIES_MAXIMUM

      public static final int DEFAULT_ENTRIES_MAXIMUM
      The default maximum for entry LRU. Currently 900 entries.
      See Also:

    • DEFAULT_MEMORY_MAXIMUM

      public static final int DEFAULT_MEMORY_MAXIMUM
      The default maximum for memory LRU. Currently 10 megabytes.
      See Also:

  • Constructor Details

    • EvictionAttributes

      public EvictionAttributes()

  • Method Details

    • createLRUEntryAttributes

      public static EvictionAttributes createLRUEntryAttributes()
      Creates and returns entry LRU eviction attributes with default action and default maximum.

      EvictionAttributes cause regions to evict the least recently used (LRU) entry once the region reaches a maximum capacity. The entry is either locally destroyed or its value overflows to disk when evicted.

      This is not supported when replication is enabled.

      For a region with DataPolicy.PARTITION, the EvictionAttribute maximum, indicates the number of entries allowed in the region, collectively for its primary buckets and redundant copies for this JVM. Once there are maximum entries in the region's primary buckets and redundant copies for this JVM, the least recently used entry will be evicted from the bucket in which the subsequent put takes place.

      If you are using a cache.xml file to create a Cache Region declaratively, you can include the following to configure a region for eviction 

               <region-attributes>
            <eviction-attributes>
               <lru-entry-count maximum="900" action="local-destroy"/>
            </eviction-attributes>
         </region-attributes>
      Returns:
      entry LRU eviction attributes with default action and default maximum

    • createLRUEntryAttributes

      public static EvictionAttributes createLRUEntryAttributes(int maximumEntries)
      Creates and returns entry LRU eviction attributes with default action and given maximumEntries.
      Parameters:
      maximumEntries - the number of entries to keep in the Region
      Returns:
      entry LRU eviction attributes with default action and maximumEntries
      See Also:

    • createLRUEntryAttributes

      public static EvictionAttributes createLRUEntryAttributes(EvictionAction evictionAction)
      Creates and returns entry LRU eviction attributes with default maximum and given evictionAction.
      Parameters:
      evictionAction - the action to perform when evicting an entry
      Returns:
      entry LRU eviction attributes with default maximum and given evictionAction
      Since:
      GemFire 8.1
      See Also:

    • createLRUEntryAttributes

      public static EvictionAttributes createLRUEntryAttributes(int maximumEntries, EvictionAction evictionAction)
      Creates and returns entry LRU eviction attributes with given evictionAction and given maximumEntries.
      Parameters:
      maximumEntries - the number of entries to keep in the Region
      evictionAction - the action to perform when evicting an entry
      Returns:
      entry LRU eviction attributes with given evictionAction and given maximumEntries
      See Also:

    • createLRUHeapAttributes

      public static EvictionAttributes createLRUHeapAttributes()
      Creates and returns heap LRU eviction attributes with default action and default sizer.

      Heap LRU EvictionAttributes evict the least recently used Region.Entry when heap usage exceeds the ResourceManager eviction heap threshold. If the eviction heap threshold is exceeded the least recently used Region.Entrys are evicted.

      With other LRU-based eviction controllers, only cache actions (such as puts and gets) cause the LRU entry to be evicted. However, with heap LRU, because the JVM's heap may be effected by more than just the GemFire cache operations, a daemon thread will perform the eviction if no operations are being done on the region.

      The eviction attribute's sizer is used to estimate how much the heap will be reduced by an eviction.

      When using Heap LRU, the JVM must be launched with the -Xmx and -Xms switches set to the same values. Many virtual machine implementations have additional JVM switches to control the behavior of the garbage collector. We suggest that you investigate tuning the garbage collector when using this type of eviction controller. A collector that frequently collects is needed to keep our heap usage up to date. In particular, on the Sun HotSpot JVM, before Java 14, the -XX:+UseConcMarkSweepGC flag needs to be set, and -XX:CMSInitiatingOccupancyFraction=N should be set with N being a percentage that is less than the ResourceManager eviction heap threshold.

      The JRockit JVM has similar flags, -Xgc:gencon and -XXgcTrigger:N, which are required if using this LRU algorithm. Please Note: the JRockit gcTrigger flag is based on heap free, not heap in use like the GemFire parameter. This means you need to set gcTrigger to 100-N. for example, if your eviction threshold is 30 percent, you will need to set gcTrigger to 70 percent.

      On the IBM JVM, the flag to get a similar collector is -Xgcpolicy:gencon, but there is no corollary to the gcTrigger/CMSInitiatingOccupancyFraction flags, so when using this feature with an IBM JVM, the heap usage statistics might lag the true memory usage of the JVM, and thresholds may need to be set sufficiently high that the JVM will initiate GC before the thresholds are crossed.

      If you are using a cache.xml file to create a Cache Region declaratively, you can include the following to create an LRU heap eviction controller: 

               <region-attributes>
            <eviction-attributes>
               <lru-heap-percentage action="local-destroy"
            </eviction-attributes>
         </region-attributes>

      Returns:
      heap LRU eviction attributes with default action and default sizer

    • createLRUHeapAttributes

      public static EvictionAttributes createLRUHeapAttributes(ObjectSizer sizer)
      Creates and returns heap LRU eviction attributes with default action and the given sizer.
      Parameters:
      sizer - the sizer implementation used to determine the size of each entry in this region
      Returns:
      heap LRU eviction attributes with default action and the given sizer
      See Also:

    • createLRUHeapAttributes

      public static EvictionAttributes createLRUHeapAttributes(ObjectSizer sizer, EvictionAction evictionAction)
      Creates and returns heap LRU eviction attributes with the given evictionAction and given sizer.
      Parameters:
      sizer - the sizer implementation used to determine the size of each entry in this region
      evictionAction - the way in which entries should be evicted
      Returns:
      heap LRU eviction attributes with the given evictionAction and given sizer
      See Also:

    • createLRUMemoryAttributes

      public static EvictionAttributes createLRUMemoryAttributes()
      Creates and returns memory LRU eviction attributes with default action, default sizer, and default maximum.

      Creates EvictionAttributes for an eviction controller that will remove the least recently used (LRU) entry from a region once the region reaches a certain byte capacity. Capacity is determined by monitoring the size of entries added and evicted. Capacity is specified in terms of megabytes. GemFire uses an efficient algorithm to determine the amount of space a region entry occupies in the JVM. However, this algorithm may not yield optimal results for all kinds of data. The user may provide their own algorithm for determining the size of objects by implementing an ObjectSizer.

      For a region with DataPolicy.PARTITION, the EvictionAttribute maximum, is always equal to " local max memory " specified for the PartitionAttributes. It signifies the amount of memory allowed in the region, collectively for its primary buckets and redundant copies for this JVM. It can be different for the same region in different JVMs.

      If you are using a cache.xml file to create a Cache Region declaratively, you can include the following to create an LRU memory eviction controller: 

                <region-attributes>
            <eviction-attributes>
               <lru-memory-size maximum="10" action="local-destroy">
                  <class-name>com.foo.MySizer</class-name>
                  <parameter name="name">
                     <string>Super Sizer</string>
                  </parameter>
               </lru-memory-size>
            </eviction-attributes>
         </region-attributes>
      Returns:
      memory LRU eviction attributes with default action, default sizer, and default maximum

    • createLRUMemoryAttributes

      public static EvictionAttributes createLRUMemoryAttributes(int maximumMegabytes)
      Creates and returns memory LRU eviction attributes with default action, default sizer, and given maximumMegabytes.

      For a region with DataPolicy.PARTITION, even if maximumMegabytes are supplied, the EvictionAttribute maximum, is always set to " local max memory " specified for the PartitionAttributes.

      Parameters:
      maximumMegabytes - the maximum allowed bytes in the Region
      Returns:
      memory LRU eviction attributes with default action, default sizer, and given maximumMegabytes
      See Also:

    • createLRUMemoryAttributes

      public static EvictionAttributes createLRUMemoryAttributes(int maximumMegabytes, ObjectSizer sizer)
      Creates and returns memory LRU eviction attributes with default action, given sizer, and given maximumMegabytes.

      For a region with DataPolicy.PARTITION, even if maximumMegabytes are supplied, the EvictionAttribute maximum, is always set to " local max memory " specified for the PartitionAttributes.

      Parameters:
      maximumMegabytes - the maximum allowed bytes in the Region
      sizer - calculates the size in bytes of the key and value for an entry.
      Returns:
      memory LRU eviction attributes with default action, given sizer, and given maximumMegabytes
      See Also:

    • createLRUMemoryAttributes

      public static EvictionAttributes createLRUMemoryAttributes(int maximumMegabytes, ObjectSizer sizer, EvictionAction evictionAction)
      Creates and returns memory LRU eviction attributes with the given evictionAction, given sizer, and given maximumMegabytes.

      For a region with DataPolicy.PARTITION, even if maximumMegabytes are supplied, the EvictionAttribute maximum, is always set to " local max memory " specified for the PartitionAttributes.

      Parameters:
      maximumMegabytes - the maximum allowed bytes in the Region
      sizer - calculates the size in bytes of the key and value for an entry.
      evictionAction - the action to take when the maximum has been reached.
      Returns:
      memory LRU eviction attributes with the given evictionAction, given sizer, and given maximumMegabytes
      See Also:

    • createLRUMemoryAttributes

      public static EvictionAttributes createLRUMemoryAttributes(ObjectSizer sizer)
      Creates and returns memory LRU eviction attributes with default action, given sizer, and default maximum.

      For a region with DataPolicy.PARTITION, even if maximumMegabytes are supplied, the EvictionAttribute maximum, is always set to " local max memory " specified for the PartitionAttributes.

      Parameters:
      sizer - calculates the size in bytes of the key and value for an entry.
      Returns:
      memory LRU eviction attributes with default action, given sizer, and default maximum
      Since:
      GemFire 6.0
      See Also:

    • createLRUMemoryAttributes

      public static EvictionAttributes createLRUMemoryAttributes(ObjectSizer sizer, EvictionAction evictionAction)
      Creates and returns memory LRU eviction attributes with given evictionAction, given sizer, and default maximum.

      For a region with DataPolicy.PARTITION, even if maximumMegabytes are supplied, the EvictionAttribute maximum, is always set to " local max memory " specified for the PartitionAttributes.

      Parameters:
      sizer - calculates the size in bytes of the key and value for an entry.
      evictionAction - the action to take when the maximum has been reached.
      Returns:
      memory LRU eviction attributes with given evictionAction, given sizer, and default maximum
      Since:
      GemFire 6.0
      See Also:

    • getObjectSizer

      public abstract ObjectSizer getObjectSizer()
      An ObjectSizer is used by the EvictionAlgorithm.LRU_MEMORY algorithm to measure the size of each Entry as it is entered into a Region. A default implementation is provided, see createLRUMemoryAttributes() for more. An ObjectSizer is used by EvictionAlgorithm.LRU_HEAP to estimate how much heap will be saved when evicting a region entry.
      Returns:
      the sizer used by EvictionAlgorithm.LRU_MEMORY or EvictionAlgorithm.LRU_HEAP, for all other algorithms null is returned.

    • getAlgorithm

      public abstract EvictionAlgorithm getAlgorithm()
      The algorithm is used to identify entries that will be evicted.
      Returns:
      a non-null EvictionAlgorithm instance reflecting the configured value or NONE when no eviction controller has been configured.

    • getMaximum

      public abstract int getMaximum()
      The unit of this value is determined by the definition of the EvictionAlgorithm set by one of the creation methods e.g. createLRUEntryAttributes().
      • If the algorithm is LRU_ENTRY then the unit is entries.
      • If the algorithm is LRU_MEMORY then the unit is megabytes.
      • If the algorithm is LRU_HEAP then the unit is undefined and this method always returns zero. Note, in geode 1.4 and earlier, this method would throw UnsupportedOperationException for LRU_HEAP.
      Returns:
      maximum value used by the EvictionAlgorithm which determines when the EvictionAction is performed.

    • getAction

      public abstract EvictionAction getAction()
      Returns:
      action that the EvictionAlgorithm takes when the maximum value is reached.

    • equals

      public boolean equals(Object obj)
      Overrides:
      equals in class Object

    • hashCode

      public int hashCode()
      Overrides:
      hashCode in class Object

    • toString

      public String toString()
      Overrides:
      toString in class Object

    • createLIFOEntryAttributes

      @Deprecated public static EvictionAttributes createLIFOEntryAttributes(int maximumEntries, EvictionAction evictionAction)
      Deprecated.
      For internal use only.
      Parameters:
      maximumEntries - the number of entries to keep in the Region
      evictionAction - the action to perform when evicting an entry
      Returns:
      an EvictionAttributes for the LIFOCapacityController
      Since:
      GemFire 5.7

    • createLIFOMemoryAttributes

      @Deprecated public static EvictionAttributes createLIFOMemoryAttributes(int maximumMegabytes, EvictionAction evictionAction)
      Deprecated.
      For internal use only.
      Parameters:
      maximumMegabytes - the maximum allowed bytes in the Region
      evictionAction - the action to perform when evicting an entry
      Returns:
      an EvictionAttributes for the MemLIFOCapacityController
      Since:
      GemFire 5.7

    • convertToConfigEvictionAttributes

      public RegionAttributesType.EvictionAttributes convertToConfigEvictionAttributes()

    • isNoEviction

      public boolean isNoEviction()