Class InMemoryState

src/java/src/org/apache/mesos/state/InMemoryState.java:33–143

An in-memory implementation of state.

 * An in-memory implementation of state.
 */
public class InMemoryState implements State {
  @Override
  public Future<Variable> fetch(String name) {
    Entry entry = entries.get(name); // Is null if doesn't exist.

    if (entry == null) {
      entry = new Entry();
      entry.name = name;
      entry.uuid = UUID.randomUUID();
      entry.value = new byte[0];

      // We use 'putIfAbsent' because multiple threads might be
      // attempting to fetch a "new" variable at the same time.
      if (entries.putIfAbsent(name, entry) != null) {
        return fetch(name);
      }
    }

    assert entry != null;

    return futureFrom((Variable) new InMemoryVariable(entry));
  }

  @Override
  public Future<Variable> store(Variable v) {
    InMemoryVariable variable = (InMemoryVariable) v;

    Entry entry = new Entry();
    entry.name = variable.entry.name;
    entry.uuid = UUID.randomUUID();
    entry.value = variable.value;

    if (entries.replace(entry.name, variable.entry, entry)) {
      return futureFrom((Variable) new InMemoryVariable(entry));
    }

    return futureFrom((Variable) null);
  }

  @Override
  public Future<Boolean> expunge(Variable v) {
    InMemoryVariable variable = (InMemoryVariable) v;

    return futureFrom(entries.remove(variable.entry.name, variable.entry));
  }

  @Override
  public Future<Iterator<String>> names() {
    return futureFrom(entries.keySet().iterator());
  }

  private static class InMemoryVariable extends Variable {
    private InMemoryVariable(Entry entry) {
      this(entry, null);
    }

    private InMemoryVariable(Entry entry, byte[] value) {
      this.entry = entry;