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Map Configuration

The following are the example configurations.

Declarative:

<hazelcast>
  <map name="default">
    <in-memory-format>BINARY</in-memory-format>
    <backup-count>0</backup-count>
    <async-backup-count>1</async-backup-count>
    <read-backup-data>true</read-backup-data>
    <time-to-live-seconds>0</time-to-live-seconds>
    <max-idle-seconds>0</max-idle-seconds>
    <eviction-policy>LRU</eviction-policy>
    <max-size policy="PER_NODE">5000</max-size>
    <eviction-percentage>25</eviction-percentage>
    <near-cache>
       <invalidate-on-change>true</invalidate-on-change>
       <cache-local-entries>false</cache-local-entries>
    <near-cache>
    <map-store enabled="true">
       <write-delay-seconds>60</write-delay-seconds>
       <write-batch-size>1000</write-batch-size>
    </map-store>
    <indexes>
        <index ordered="true">id</index>
        <index ordered="false">name</index>
    </indexes>
    <entry-listeners>
        <entry-listener include-value="true" local="false">
           com.hazelcast.examples.EntryListener
        </entry-listener>
    </entry-listeners>   
  </map>
</hazelcast>

Programmatic:

MapConfig mapConfig = new MapConfig();
mapConfig.setName( "default" ).setInMemoryFormat( "BINARY" );

mapConfig.setBackupCount( "0" ).setAsyncBackupCount( "1" )
         .setReadBackupData( "true" );

MapStoreConfig mapStoreConfig = mapConfig.getMapStoreConfig();
mapStoreConfig.setWriteDelaySeconds( "60" )
              .setWriteBatchSize( "1000" );

MapIndexConfig mapIndexConfig = mapConfig.getMapIndexConfig();
mapIndexConfig.setAttribute( "id" ).setOrdered( "true" );
mapIndexConfig.setAttribute( "name" ).setOrdered( "false" );

It has below elements.

  • in-memory-format: Determines how the data will be stored in memory. It has two values: BINARY and OBJECT. BINARY is the default option and enables to store the data in serialized binary format. If OBJECT is set as the value, data will be stored in deserialized form.
  • backup-count: Defines the count of synchronous backups. If it is set as 1, for example, backup of a partition will be placed on another node. If it is 2, it will be placed on 2 other nodes.
  • async-backup-count: Defines the count of synchronous backups. Count behavior is the same as that of backup-count element.
  • read-backup-data: This boolean element enables reading local backup entries when set as true.
  • time-to-live-seconds: Maximum time in seconds for each entry to stay in the map.
  • max-idle-seconds: Maximum time in seconds for each entry to stay idle in the map.
  • eviction-policy: Policy for evicting entries. It has three values: NONE, LRU (Least Recently Used) and LFU (Least Frequently Used). If set as NONE, no items will be evicted.
  • max-size: Maximum size of the map (i.e. maximum entry count of the map). When maximum size is reached, map is evicted based on the eviction policy defined. It has four attributes: PER_NODE (Maximum number of map entries in each JVM), PER_PARTITION (Maximum number of map entries within each partition), USED_HEAP_SIZE (Maximum used heap size in megabytes for each JVM) and USED_HEAP_PERCENTAGE (Maximum used heap size percentage for each JVM).
  • eviction-percentage: When max-size is reached, specified percentage of the map will be evicted.
  • merge-policy: Policy for merging maps after a split-brain syndrome was detected and the different network partitions need to be merged. Available merge policy classes are explained below:
    • HigherHitsMapMergePolicy causes the merging entry to be merged from source to destination map if source entry has more hits than the destination one.
    • LatestUpdateMapMergePolicy causes the merging entry to be merged from source to destination map if source entry has updated more recently than the destination entry. This policy can only be used of the clocks of the machines are in sync.
    • PassThroughMergePolicy causes the merging entry to be merged from source to destination map unless merging entry is null. PutIfAbsentMapMergePolicy causes the merging entry to be merged from source to destination map if it does not exist in the destination map.
  • statistics-enabled: You can retrieve statistics information like owned entry count, backup entry count, last update time, locked entry count by setting this element's value to true. The method for retrieving the statistics is getLocalMapStats().
  • wan-replication-ref: Hazelcast can replicate some or all of the cluster data. For example, you can have 5 different maps but you want only one of these maps replicating across clusters. To achieve this you mark the maps to be replicated by adding this element in the map configuration.
  • optimize-queries: This element is used to increase the speed of query processes in the map. It only works when in-memory-format is set as BINARY and performs a pre-caching on the entries queried.

Map Store

  • class-name: Name of the class implementing MapLoader and/or MapStore.
  • write-delay-seconds: Number of seconds to delay to call the MapStore.store(key, value). If the value is zero then it is write-through so MapStore.store(key, value) will be called as soon as the entry is updated. Otherwise it is write-behind so updates will be stored after write-delay-seconds value by calling Hazelcast.storeAll(map). Default value is 0.
  • write-batch-size: Used to create batch chunks when writing map store. In default mode all entries will be tried to persist in one go. To create batch chunks, minimum meaningful value for write-batch-size is 2. For values smaller than 2, it works as in default mode.

Near Cache

Most of map near cache properties have the same names and tasks explained in map properties above. Below are the ones specific to near cache.

  • invalidate-on-change: Determines whether the cached entries get evicted if the entries are updated or removed).
  • cache-local-entries: If you want the local entries to be cached, set this element's value to true.

Indexes

This configuration lets you index the attributes of an object in the map and also order these attributes. See the example declarative and programmatic configuration.

Entry Listeners

This configuration lets you add listeners (listener classes) for the map entries. You can also set the attributes include-value to true if you want the entry event to contain the entry values and local to true if you want to listen to the entries on the local node.