Annotation.java

/**
 * Copyright 2015-2016 The OpenZipkin Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */
package zipkin;

import zipkin.internal.Nullable;

import static zipkin.internal.Util.checkNotNull;
import static zipkin.internal.Util.equal;

/**
 * Associates an event that explains latency with a timestamp.
 *
 * <p>Unlike log statements, annotations are often codes: Ex. {@link Constants#SERVER_RECV "sr"}.
 */
public final class Annotation implements Comparable<Annotation> {

  public static Annotation create(long timestamp, String value, @Nullable Endpoint endpoint) {
    return new Annotation(timestamp, value, endpoint);
  }

  /**
   * Microseconds from epoch.
   *
   * <p>This value should be set directly by instrumentation, using the most precise value possible.
   * For example, {@code gettimeofday} or multiplying {@link System#currentTimeMillis} by 1000.
   */
  public final long timestamp;

  /**
   * Usually a short tag indicating an event, like {@link Constants#SERVER_RECV "sr"}. or {@link
   * Constants#ERROR "error"}
   */
  public final String value;

  /** The host that recorded {@link #value}, primarily for query by service name. */
  @Nullable
  public final Endpoint endpoint;

  Annotation(long timestamp, String value, Endpoint endpoint) {
    this.timestamp = timestamp;
    this.value = checkNotNull(value, "value");
    this.endpoint = endpoint;
  }

  public Builder toBuilder(){
    return new Builder(this);
  }

  public static Builder builder(){
    return new Builder();
  }

  public static final class Builder {
    private Long timestamp;
    private String value;
    private Endpoint endpoint;

    Builder() {
    }

    Builder(Annotation source) {
      this.timestamp = source.timestamp;
      this.value = source.value;
      this.endpoint = source.endpoint;
    }

    /** @see Annotation#timestamp */
    public Builder timestamp(long timestamp) {
      this.timestamp = timestamp;
      return this;
    }

    /** @see Annotation#value */
    public Builder value(String value) {
      this.value = value;
      return this;
    }

    /** @see Annotation#endpoint */
    public Builder endpoint(Endpoint endpoint) {
      this.endpoint = endpoint;
      return this;
    }

    public Annotation build() {
      return Annotation.create(timestamp, value, endpoint);
    }
  }

  @Override
  public boolean equals(Object o) {
    if (o == this) {
      return true;
    }
    if (o instanceof Annotation) {
      Annotation that = (Annotation) o;
      return (this.timestamp == that.timestamp)
          && (this.value.equals(that.value))
          && equal(this.endpoint, that.endpoint);
    }
    return false;
  }

  @Override
  public int hashCode() {
    int h = 1;
    h *= 1000003;
    h ^= (timestamp >>> 32) ^ timestamp;
    h *= 1000003;
    h ^= value.hashCode();
    h *= 1000003;
    h ^= (endpoint == null) ? 0 : endpoint.hashCode();
    return h;
  }

  /** Compares by {@link #timestamp}, then {@link #value}. */
  @Override
  public int compareTo(Annotation that) {
    if (this == that) return 0;
    int byTimestamp = timestamp < that.timestamp ? -1 : timestamp == that.timestamp ? 0 : 1;
    if (byTimestamp != 0) return byTimestamp;
    return value.compareTo(that.value);
  }
}