Name

no

A unique identifier for the HDFSStore

NameNodeURL

no

HDFSStore persists data on a HDFS cluster identified by cluster's NameNode URL or NameNode Service URL. NameNode URL can also be provided via hdfs-site.xml (see HDFSClientConfigFile). If the NameNode url is missing HDFSStore creation will fail. HDFS client can also load hdfs configuration files in the classpath. NameNode URL provided in this way is also fine.

HomeDir

no

The HDFS directory path in which HDFSStore stores files. The value must not contain the NameNode URL. The owner of this node's JVM process must have read and write access to this directory. The path could be absolute or relative. If a relative path for HomeDir is provided, then the HomeDir is created relative to /user/JVM_owner_name or, if specified, relative to directory specified by the hdfs-root-dir property.

As a best practice, HDFS store directories should be created relative to a single HDFS root directory. As an alternative, an absolute path beginning with the "/" character to override the default root location can be provided.

HDFSClientConfigFile

no

The full path to the HDFS client configuration file, for e.g. hdfs-site.xml or core-site.xml. This file must be accessible to any node where an instance of this HDFSStore will be created. If each node has a local copy of this configuration file, it is important for all the copies to be "identical". Alternatively, by default HDFS client can also load some HDFS configuration files if added in the classpath.

MaxMemory

yes

The maximum amount of memory in megabytes used by HDFSStore. HDFSStore buffers data in memory to optimize HDFS IO operations. Once the configured memory is utilized, data may overflow to disk.

ReadCacheSize

no

The maximum amount of memory in megabytes used by HDFSStore read cache. HDFSStore can cache data in memory to optimize HDFS IO operations. Read cache shares memory allocated to HDFSStore. Increasing read cache memory can improve the read performance.

BatchSize

yes

HDFSStore buffer data is persisted on HDFS in batches, and the BatchSize defines the maximum size (in megabytes) of each batch that is written to HDFS. This parameter, along with BatchInterval determines the rate at which data is persisted on HDFS.

BatchInterval

yes

HDFSStore buffer data is persisted on HDFS in batches, and the BatchInterval defines the maximum time that can elapse between writing batches to HDFS. This parameter, along with BatchSize determines the rate at which data is persisted on HDFS.

DispatcherThreads

no

The maximum number of threads (per region) used to write batches of HDFS. If you have a large number of clients that add or update data in a region, then you may need to increase the number of dispatcher threads to avoid bottlenecks when writing data to HDFS.

BufferPersistent

no

Configure if HDFSStore in-memory buffer data, that has not been persisted on HDFS yet, should be persisted to a local disk to buffer prevent data loss. Persisting data may impact write performance. If performance is critical and buffer data loss is acceptable, disable persistence.

DiskStore

no

The named DiskStore to use for any local disk persistence needs of HDFSStore, for e.g. store's buffer persistence and buffer overflow. If you specify a value, the named DiskStore must exist. If you specify a null value or you omit this option, default DiskStore is used.

SynchronousDiskWrite

no

Include the isSynchronous option to enable or disable synchronous writes to the local DiskStore.

PurgeInterval

yes

HDFSStore creates new files as part of periodic maintenance activity. Existing files are deleted asynchronously. PurgeInterval defines the amount of time old files remain available for MapReduce jobs. After this interval has passed, old files are deleted.

MajorCompaction

yes

Major compaction removes old values of a key and deleted records from the HDFS files, which can save space in HDFS and improve performance when reading from HDFS. As major compaction process can be long-running and I/O-intensive, tune the performance of major compaction using MajorCompactionInterval and MajorCompactionThreads.

MajorCompactionInterval

yes

The amount of time after which HDFSStore performs the next major compaction cycle.

MajorCompactionThreads

yes

The maximum number of threads that HDFSStore uses to perform major compaction. You can increase the number of threads used for compactions on different buckets as necessary in order to fully utilize the performance of your HDFS cluster and its disks.

MinorCompaction

yes

Minor compaction reorganizes data in files to optimize read performance and reduce number of files created on HDFS. Minor compaction process can be I/O-intensive, tune the performance of minor compaction using MinorCompactionThreads.

MinorCompactionThreads

yes

The maximum number of threads that HDFSStore uses to perform minor compaction. You can increase the number of threads used for compactions on different buckets as necessary in order to fully utilize the performance of your HDFS cluster and its disks.

MaxWriteOnlyFileSize

yes

For HDFS write-only regions, this defines the maximum size (in megabytes) that an HDFS log file can reach before HDFSStore closes the file and begins writing to a new file. This clause is ignored for HDFS read/write regions. Keep in mind that the files are not available for MapReduce processing until the file is closed; you can also set WriteOnlyFileRolloverInterval to specify the maximum amount of time an HDFS log file remains open.

WriteOnlyFileRolloverInterval

yes

For HDFS write-only regions, this defines the maximum time that can elapse before HDFSStore closes an HDFS file and begins writing to a new file. This clause is ignored for HDFS read/write regions.