public String getHostName() {
    return hostName;
  }
Gets the name of the host that the alert is for. Some alerts do not run
against hosts, such as aggregate alert definitions, so this may be
{@code null}.

@return the name of the host or {@code null} if none.
ambari-server/src/main/java/org/apache/ambari/server/orm/entities/AlertHistoryEntity.java