com.datastax.driver.core.policies.ReconnectionPolicy Maven / Gradle / Ivy
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/*
* Copyright DataStax, Inc.
*
* 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 com.datastax.driver.core.policies;
import com.datastax.driver.core.Cluster;
/**
* Policy that decides how often the reconnection to a dead node is attempted.
*
* Each time a node is detected dead (because a connection error occurs), a new {@code
* ReconnectionSchedule} instance is created (through the {@link #newSchedule()}). Then each call to
* the {@link ReconnectionSchedule#nextDelayMs} method of this instance will decide when the next
* reconnection attempt to this node will be tried.
*
*
Note that if the driver receives a push notification from the Cassandra cluster that a node is
* UP, any existing {@code ReconnectionSchedule} on that node will be cancelled and a new one will
* be created (in effect, the driver reset the scheduler).
*
*
The default {@link ExponentialReconnectionPolicy} policy is usually adequate.
*/
public interface ReconnectionPolicy {
/**
* Creates a new schedule for reconnection attempts.
*
* @return the created schedule.
*/
public ReconnectionSchedule newSchedule();
/** Schedules reconnection attempts to a node. */
public interface ReconnectionSchedule {
/**
* When to attempt the next reconnection.
*
*
This method will be called once when the host is detected down to schedule the first
* reconnection attempt, and then once after each failed reconnection attempt to schedule the
* next one. Hence each call to this method are free to return a different value.
*
* @return a time in milliseconds to wait before attempting the next reconnection.
*/
public long nextDelayMs();
}
/**
* Gets invoked at cluster startup.
*
* @param cluster the cluster that this policy is associated with.
*/
void init(Cluster cluster);
/**
* Gets invoked at cluster shutdown.
*
*
This gives the policy the opportunity to perform some cleanup, for instance stop threads
* that it might have started.
*/
void close();
}