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Service for batching and relaying metric traffic to Wavefront

There is a newer version: 9999.0

package com.wavefront.agent.queueing;

import com.wavefront.agent.data.DataSubmissionTask;

import javax.annotation.Nonnull;
import javax.annotation.Nullable;
import java.io.IOException;

/**
 * Proxy-specific queue interface, which is basically a wrapper for a Tape queue. This allows us to
 * potentially support more than one backing storage in the future.
 *
 * @param  type of objects stored.
 *
 * @author [email protected].
 */
public interface TaskQueue> extends Iterable {

  /**
   * Retrieve a task that is currently at the head of the queue.
   *
   * @return task object
   */
  @Nullable
  T peek();

  /**
   * Add a task to the end of the queue
   *
   * @param entry task
   * @throws IOException IO exceptions caught by the storage engine
   */
  void add(@Nonnull T entry) throws IOException;

  /**
   * Remove a task from the head of the queue. Requires peek() to be called first, otherwise
   * an {@code IllegalStateException} is thrown.
   *
   * @throws IOException IO exceptions caught by the storage engine
   */
  void remove() throws IOException;

  /**
   * Empty and re-initialize the queue.
   */
  void clear() throws IOException;

  /**
   * Returns a number of tasks currently in the queue.
   *
   * @return number of tasks
   */
  int size();

  /**
   * Close the queue. Should be invoked before a graceful shutdown.
   */
  void close() throws IOException;

  /**
   * Returns the total weight of the queue (sum of weights of all tasks).
   *
   * @return weight of the queue (null if unknown)
   */
  @Nullable
  Long weight();

  /**
   * Returns the total number of pre-allocated but unused bytes in the backing file.
   * May return null if not applicable.
   *
   * @return total number of available bytes in the file or null
   */
  @Nullable
  Long getAvailableBytes();
}