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The Apache Cassandra Project develops a highly scalable second-generation distributed database, bringing together Dynamo's fully distributed design and Bigtable's ColumnFamily-based data model.

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/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.cassandra.utils;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

import static org.apache.cassandra.utils.Nemesis.Traffic.HIGH;

/**
 * Annotate fields, particularly important volatile fields, where the system should adversarially schedule
 * thread events around memory accesses (read or write).
 *
 * This can introduce significant simulation overhead, so should be used sparingly.
 *
 * TODO: Support @Nemesis on methods, to insert nemesis points either before or after invocations of the method
 */
@Retention(RetentionPolicy.RUNTIME)
@Target({ ElementType.FIELD, ElementType.METHOD })
public @interface Nemesis
{
    enum Traffic { LOW, HIGH }

    Traffic traffic() default HIGH;
}