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/*
* Copyright © 2016-2018 European Support Limited
*
* 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 org.openecomp.sdc.logging.context;
import java.net.InetAddress;
import java.net.UnknownHostException;
/**
* Holds a reference to local host address as returned by Java runtime. A value of host address will be cached for the
* interval specified in the constructor or {@link #DEFAULT_REFRESH_INTERVAL}. The caching helps to avoid many low-level
* calls, but at the same time pick up any IP or FQDN changes. Although the underlying JDK implementation uses caching
* too, the refresh interval for logging may be much longer due to the nature of the use.
*
* @author evitaliy
* @since 26 Mar 2018
*/
@SuppressWarnings({"UseOfSystemOutOrSystemErr", "CallToPrintStackTrace", "squid:S106", "squid:S1148"})
public class HostAddress {
private static final long DEFAULT_REFRESH_INTERVAL = 60000L; // 1 min
private final long interval;
private CacheEntry cachedAddress;
public HostAddress() {
this(DEFAULT_REFRESH_INTERVAL);
}
/**
* Creates a cache for host address with a custom refresh interval.
*/
public HostAddress(long refreshInterval) {
this.interval = refreshInterval;
this.cachedAddress = new CacheEntry(System.currentTimeMillis(), read());
}
/**
* Returns an address (host name and IP address) of the local system.
*
* @return local host address or <code>null</code> if it could not be read for some reason
*/
public synchronized InetAddress get() {
long current = System.currentTimeMillis();
if (current - cachedAddress.lastUpdated < interval) {
return cachedAddress.address;
}
InetAddress address = read();
cachedAddress = new CacheEntry(current, address);
return address;
}
private InetAddress read() {
try {
return InetAddress.getLocalHost();
} catch (UnknownHostException e) {
e.printStackTrace(); // can't really use logging
return null; // let register the attempt even if failed
}
}
private static class CacheEntry {
private final long lastUpdated;
private final InetAddress address;
private CacheEntry(long lastUpdated, InetAddress address) {
this.lastUpdated = lastUpdated;
this.address = address;
}
}
}
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