net.logstash.logback.appender.destination.PreferPrimaryDestinationConnectionStrategy Maven / Gradle / Ivy
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/*
* Copyright 2013-2021 the original author or 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 net.logstash.logback.appender.destination;
import ch.qos.logback.core.util.Duration;
/**
* The first destination is considered the "primary" destination.
* The remaining destinations are considered "secondary" destinations.
*
* Prefer to connect to the primary destination.
* If the primary destination is down, try other destinations.
*
*
* Connections are attempted to each destination in order until a connection succeeds.
* Logs will be sent to the first destination for which the connection succeeds
* until the connection breaks or (if the connection is to a secondary destination)
* the {@link #secondaryConnectionTTL} elapses.
*/
public class PreferPrimaryDestinationConnectionStrategy implements DestinationConnectionStrategy {
/**
* The "primary" destination index;
*/
private static final int PRIMARY_DESTINATION_INDEX = 0;
/**
* Time period for connections to secondary destinations to be used
* before attempting to reconnect to primary destination.
*
* When the value is null (the default), the feature is disabled:
* the appender will stay on the current destination until an error occurs.
*/
private Duration secondaryConnectionTTL;
/**
* The minimum amount of time that a connection must remain open
* before the primary is retried on the next reopen attempt.
*
*
This is used to prevent a connection storm against the primary if the primary
* accepts connections and then immediately closes them.
*
* When null, the primary will always be retried first,
* regardless of how long the previous connection remained open.
*/
private Duration minConnectionTimeBeforePrimary = Duration.buildBySeconds(10);
/**
* The destinationIndex to be returned on the next call to {@link #selectNextDestinationIndex(int, int)}.
*/
private volatile int nextDestinationIndex = PRIMARY_DESTINATION_INDEX;
/**
* Time at which the current connection should be automatically closed
* to force an attempt to reconnect to the primary server
*/
private volatile long secondaryConnectionExpirationTime = Long.MAX_VALUE;
private volatile long lastSuccessfulConnectTime;
@Override
public int selectNextDestinationIndex(int previousDestinationIndex, int numDestinations) {
int candidateIndex = this.nextDestinationIndex; // volatile read
if (candidateIndex == PRIMARY_DESTINATION_INDEX
&& minConnectionTimeBeforePrimary != null
&& (System.currentTimeMillis() - lastSuccessfulConnectTime) < minConnectionTimeBeforePrimary.getMilliseconds()) {
/*
* If the connection didn't remain open for at least the minConnectionTimeBeforePrimary,
* then keep trying destinations in round-robin.
*
* This prevents a connection storm against the primary if the primary
* accepts connections and then immediately closes them.
*/
return (previousDestinationIndex + 1) % numDestinations;
}
return nextDestinationIndex;
}
@Override
public void connectSuccess(long connectionStartTimeInMillis, int connectedDestinationIndex, int numDestinations) {
/*
* If connected to a secondary, remember when the connection should be closed to
* force attempt to reconnect to primary
*/
if (secondaryConnectionTTL != null && connectedDestinationIndex != PRIMARY_DESTINATION_INDEX) {
secondaryConnectionExpirationTime = connectionStartTimeInMillis + secondaryConnectionTTL.getMilliseconds();
} else {
secondaryConnectionExpirationTime = Long.MAX_VALUE;
}
lastSuccessfulConnectTime = connectionStartTimeInMillis;
nextDestinationIndex = PRIMARY_DESTINATION_INDEX;
}
@Override
public void connectFailed(long connectionStartTimeInMillis, int failedDestinationIndex, int numDestinations) {
nextDestinationIndex = (failedDestinationIndex + 1) % numDestinations;
}
@Override
public boolean shouldReconnect(long currentTimeInMillis, int currentDestinationIndex, int numDestinations) {
return secondaryConnectionExpirationTime <= currentTimeInMillis;
}
public Duration getSecondaryConnectionTTL() {
return secondaryConnectionTTL;
}
/**
* Time period for connections to secondary destinations to be used
* before attempting to reconnect to primary destination.
*
* When the value is null (the default), the feature is disabled:
* the appender will stay on the current destination until an error occurs.
*
* @param secondaryConnectionTTL time to stay connected to a secondary connection
* before attempting to reconnect to the primary
*/
public void setSecondaryConnectionTTL(Duration secondaryConnectionTTL) {
if (secondaryConnectionTTL != null && secondaryConnectionTTL.getMilliseconds() <= 0) {
throw new IllegalArgumentException("secondaryConnectionTTL must be > 0");
}
this.secondaryConnectionTTL = secondaryConnectionTTL;
}
public Duration getMinConnectionTimeBeforePrimary() {
return minConnectionTimeBeforePrimary;
}
/**
* The minimum amount of time that a connection must remain open
* before the primary is retried on the next reopen attempt.
*
* This is used to prevent a connection storm against the primary if the primary
* accepts connections and then immediately closes them.
*
* When null, the primary will always be retried first,
* regardless of how long the previous connection remained open.
*
* @param minConnectionTimeBeforePrimary The minimum amount of time that a connection must remain open
* before the primary is retried on the next reopen attempt.
*/
public void setMinConnectionTimeBeforePrimary(Duration minConnectionTimeBeforePrimary) {
this.minConnectionTimeBeforePrimary = minConnectionTimeBeforePrimary;
}
}