// 1. Open bdb Environment
EnvironmentConfig envConfig = new EnvironmentConfig();
envConfig.setAllowCreate(true);
Environment bdbEnv = new Environment(new File("/tmp/bdb_data"), envConfig);

// 2. Open the database
DatabaseConfig dbConfig = new DatabaseConfig();
dbConfig.setAllowCreate(true);
Database db = myDbEnvironment.openDatabase(null, "db_name", dbConfig);

// 3. Writing records to bdb
String key = "key";
String value = "value";
DatabaseEntry theKey = new DatabaseEntry(key.getBytes("UTF-8"));
DatabaseEntry theData = new DatabaseEntry(value.getBytes("UTF-8"));
db.put(null, theKey, theData);

// 4. Getting records from bdb
DatabaseEntry theKey = new DatabaseEntry(key.getBytes("UTF-8"));
DatabaseEntry theData = new DatabaseEntry();
if (db.get(null, theKey, theData, LockMode.DEFAULT) == OperationStatus.SUCCESS) {
byte[] datas = theData.getData();
String value = new String(datas, "UTF-8");
} else {
// Get Failed.
}

Berkeley DB Java Edition High Availability

Berkeley DB Java Edition High Availability is a replicated, single-master, embedded database engine based on Berkeley DB Java Edition. JE HA offers important improvements in application availability, as well as offering improved read scalability and performance. JE HA does this by extending the data guarantees offered by a traditional transactional system to processes running on multiple physical hosts.

Replication Group Members

Processes that take part in a JE HA application are generically called nodes. Most nodes serve as a read-only Replica. One node in the HA application can perform database writes. This is the Master node.

The sum totality of all the nodes taking part in the replicated application is called the replication group.

Replication groups consist of electable nodes and, optionally, Monitor and Secondary nodes.

Electable nodes are replication group members that can be elected to become the group's Master node through a replication election.

Secondary nodes also have access to a JE environment, but can only serve as read-only replicas, not masters, and do not participate in elections.

Monitor nodes do not have access to a JE environment and do not participate in elections.

Note that all nodes in a replication group have a unique group-wide name.

Replicated Environments

Every electable or secondary node manages a single replicated JE environment directory. The environment follows the usual regulations governing a JE environment; namely, only a single read/write process can access the environment at a single point in time.

However, to provide for the underlying infrastructure needed to implement replication, your JE HA application must instead use the ReplicatedEnvironment class, which is a subclass of Environment. Its constructor accepts the normal environment configuration properties using the EnvironmentConfig class, just as you would normally configure an Environment object. However, the ReplicatedEnvironment class also accepts an ReplicationConfig class object, which allows you to manage the properties specific to replication.

HelperHosts

Used to join replica group

// TODO

Example

Node-1

// 1. Config Environment
EnvironmentConfig envConfig = new EnvironmentConfig();
envConfig.setAllowCreate(true);

// 2. Config replica-group-name and node identify
ReplicationConfig repConfig = new ReplicationConfig();
repConfig.setGroupName("BDB-Replica-Group-Name");
repConfig.setNodeName("Node-1");
repConfig.setNodeHostPort("127.0.0.1:9613");

// 3. Config htlper hosts, used to join the ReplicaGroup
repConfig.setHelperHosts("127.0.0.1:9613");

// 4. Open ReplicatedEnvironment
ReplicatedEnvironment repEnv =
new ReplicatedEnvironment(envHome, repConfig, envConfig);

// 5. Open the database
DatabaseConfig dbConfig = new DatabaseConfig();
dbConfig.setAllowCreate(true);
Database db = myDbEnvironment.openDatabase(null, "db_name", dbConfig);

// 6. Writing records to bdb
String key = "key";
String value = "value";
DatabaseEntry theKey = new DatabaseEntry(key.getBytes("UTF-8"));
DatabaseEntry theData = new DatabaseEntry(value.getBytes("UTF-8"));
db.put(null, theKey, theData);

// 7. Getting records from bdb
DatabaseEntry theKey = new DatabaseEntry(key.getBytes("UTF-8"));
DatabaseEntry theData = new DatabaseEntry();
if (db.get(null, theKey, theData, LockMode.DEFAULT) == OperationStatus.SUCCESS) {
byte[] datas = theData.getData();
String value = new String(datas, "UTF-8");
} else {
// Get Failed.
}