Hector (API)

As Cassandra is shipped with the low-level Thrift (protocol), there was a potential to develop a better protocol for application developers. Hector was developed by Ran Tavory as a high-level interface that overlays the shortcomings of Thrift. It is licensed with the MIT License that allows to use, modify, split and change the design.

The high-level features of Hector are[2]

• A high-level object oriented interface to Cassandra: It is mainly inspired by the Cassandra-java-client. The API is defined in the Keyspace interface.
• Connection pooling. As in high-scale applications, the usual pattern for DAOs is a large number of reads/writes. It is too expensive for clients to open new connections with each request. So, a client may easily run out of available sockets, if it operates fast enough. Hector provides connection pooling and a nice framework that manages the details.
• Failover support: As Cassandra is a distributed data store where hosts (nodes) may go down. Hector has its own failover policy.

• JMX support: Hector exposes JMX for many important runtime metrics, such as number of available connections, idle connections, error statistics.
• Load balancing: A simple load balancing exists in the newer version.[5]
• Supports the command design pattern to allow clients to concentrate on their business logic and let Hector take care of the required plumbing.

As an example, an implementation of a simple distributed hashtable over Cassandra is listed.

 /**
   * Insert a new value keyed by key
   * @param key Key for the value
   * @param value the String value to insert
   */
  public void insert(final String key, final String value) throws Exception {
    execute(new Command(){
      public Void execute(final Keyspace ks) throws Exception {
        ks.insert(key, createColumnPath(COLUMN_NAME), bytes(value));
        return null;
      }
    });
  }

  /**
   * Get a string value.
   * @return The string value; null if no value exists for the given key.
   */
  public String get(final String key) throws Exception {
    return execute(new Command(){
      public String execute(final Keyspace ks) throws Exception {
        try {
          return string(ks.getColumn(key, createColumnPath(COLUMN_NAME)).getValue());
        } catch (NotFoundException e) {
          return null;
        }
      }
    });
  }

  /**
   * Delete a key from cassandra
   */
  public void delete(final String key) throws Exception {
    execute(new Command(){
      public Void execute(final Keyspace ks) throws Exception {
        ks.remove(key, createColumnPath(COLUMN_NAME));
        return null;
      }
    });
  }

• Apache Thrift
• Hector on github
• The Cassandra Java client