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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.
/*
* 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.locator;
import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.Map;
import java.util.List;
public interface DynamicEndpointSnitchMBean
{
public Map getScores();
public int getUpdateInterval();
public int getResetInterval();
public double getBadnessThreshold();
public String getSubsnitchClassName();
public List dumpTimings(String hostname) throws UnknownHostException;
/**
* Setting a Severity allows operators to inject preference information into the Dynamic Snitch
* replica selection.
*
* When choosing which replicas to participate in a read request, the DSnitch sorts replicas
* by response latency, and selects the fastest replicas. Latencies are normalized to a score
* from 0 to 1, with lower scores being faster.
*
* The Severity injected here will be added to the normalized score.
*
* Thus, adding a Severity greater than 1 will mean the replica will never be contacted
* (unless needed for ALL or if it is added later for rapid read protection).
*
* Conversely, adding a negative Severity means the replica will *always* be contacted.
*
* (The "Severity" term is historical and dates to when this was used to represent how
* badly background tasks like compaction were affecting a replica's performance.
* See CASSANDRA-3722 for when this was introduced and CASSANDRA-11738 for why it was removed.)
*/
public void setSeverity(double severity);
/**
* @return the current manually injected Severity.
*/
public double getSeverity();
}