RocksDB JNI

Description

RocksDB JNI gives you a Java interface to the RocksDB C++ library which is an embeddable persistent key-value store for fast storage.

API Usage:

Recommended Package imports:

import org.iq80.rocksdb.*;
import static org.fusesource.rocksdbjni.JniDBFactory.*;
import java.io.*;

Opening and closing the database.

Options options = new Options();
options.createIfMissing(true);
DB db = factory.open(new File("example"), options);
try {
  // Use the db in here....
} finally {
  // Make sure you close the db to shutdown the 
  // database and avoid resource leaks.
  db.close();
}

Putting, Getting, and Deleting key/values.

db.put(bytes("Tampa"), bytes("rocks"));
String value = asString(db.get(bytes("Tampa")));
db.delete(bytes("Tampa"));

Performing Batch/Bulk/Atomic Updates.

WriteBatch batch = db.createWriteBatch();
try {
  batch.delete(bytes("Denver"));
  batch.put(bytes("Tampa"), bytes("green"));
  batch.put(bytes("London"), bytes("red"));

  db.write(batch);
} finally {
  // Make sure you close the batch to avoid resource leaks.
  batch.close();
}

Iterating key/values.

DBIterator iterator = db.iterator();
try {
  for(iterator.seekToFirst(); iterator.hasNext(); iterator.next()) {
    String key = asString(iterator.peekNext().getKey());
    String value = asString(iterator.peekNext().getValue());
    System.out.println(key+" = "+value);
  }
} finally {
  // Make sure you close the iterator to avoid resource leaks.
  iterator.close();
}

Working against a Snapshot view of the Database.

ReadOptions ro = new ReadOptions();
ro.snapshot(db.getSnapshot());
try {
  
  // All read operations will now use the same 
  // consistent view of the data.
  ... = db.iterator(ro);
  ... = db.get(bytes("Tampa"), ro);

} finally {
  // Make sure you close the snapshot to avoid resource leaks.
  ro.snapshot().close();
}

Using a custom Comparator.

DBComparator comparator = new DBComparator(){
    public int compare(byte[] key1, byte[] key2) {
        return new String(key1).compareTo(new String(key2));
    }
    public String name() {
        return "simple";
    }
    public byte[] findShortestSeparator(byte[] start, byte[] limit) {
        return start;
    }
    public byte[] findShortSuccessor(byte[] key) {
        return key;
    }
};
Options options = new Options();
options.comparator(comparator);
DB db = factory.open(new File("example"), options);

Disabling Compression

Options options = new Options();
options.compressionType(CompressionType.NONE);
DB db = factory.open(new File("example"), options);

Getting approximate sizes.

long[] sizes = db.getApproximateSizes(new Range(bytes("a"), bytes("k")), new Range(bytes("k"), bytes("z")));
System.out.println("Size: "+sizes[0]+", "+sizes[1]);

Getting database status.

String stats = db.getProperty("rocksdb.stats");
System.out.println(stats);

Destroying a database.

Options options = new Options();
factory.destroy(new File("example"), options);

Repairing a database.

Options options = new Options();
factory.repair(new File("example"), options);

Using a memory pool to make native memory allocations more efficient:

JniDBFactory.pushMemoryPool(1024 * 512);
try {
    // .. work with the DB in here, 
} finally {
    JniDBFactory.popMemoryPool();
}

Building

Prerequisites

• GNU compiler toolchain
• Maven 3

Supported Platforms

The following worked for me on:

• OS X Lion with X Code 4
• CentOS 5.6 (32 and 64 bit)
• Ubuntu 12.04 (32 and 64 bit)
  • apt-get install autoconf libtool

Build Procedure

Then download the snappy, rocksdb, and rocksdbjni project source code:

wget http://snappy.googlecode.com/files/snappy-1.0.5.tar.gz
tar -zxvf snappy-1.0.5.tar.gz
git clone [email protected]:facebook/rocksdb.git
git clone git://github.com/fusesource/rocksdbjni.git
export SNAPPY_HOME=`cd snappy-1.0.5; pwd`
export ROCKSDB_HOME=`cd rocksdb; pwd`
export ROCKSDBJNI_HOME=`cd rocksdbjni; pwd`

Compile the snappy project. This produces a static library.

cd ${SNAPPY_HOME}
./configure --disable-shared --with-pic
make

Patch and Compile the rocksdb project. This produces a static library.

cd ${ROCKSDB_HOME}
export LIBRARY_PATH=${SNAPPY_HOME}
export C_INCLUDE_PATH=${LIBRARY_PATH}
export CPLUS_INCLUDE_PATH=${LIBRARY_PATH}
make librocksdb.a

Now use maven to build the rocksdbjni project.

cd ${ROCKSDBJNI_HOME}
mvn clean install

The cd to the platform specific directory that matches your platform

• rocksdbjni-osx
• rocksdbjni-linux32
• rocksdbjni-linux64
• rocksdbjni-win32
• rocksdbjni-win64

And then run:

mvn clean install

Build Results

• rocksdbjni/target/rocksdbjni-${version}.jar : The java class file to the library.
• rocksdbjni/target/rocksdbjni-${version}-native-src.zip : A GNU style source project which you can use to build the native library on other systems.
• rocksdbjni-${platform}/target/rocksdbjni-${platform}-${version}.jar : A jar file containing the built native library using your currently platform.