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// Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.vespa.config.server.host;
import java.util.*;
import java.util.concurrent.ConcurrentHashMap;
import java.util.logging.Logger;
import com.google.common.base.Predicate;
import com.google.common.collect.Collections2;
import com.yahoo.log.LogLevel;
/**
* A host registry that create mappings between some type T and a list of hosts, represented as
* strings.
* TODO: Maybe we should have a Host type, but using String for now.
* TODO: Is there a generalized version of this pattern? Need some sort mix of Bimap and Multimap
*
* @author lulf
* @since 5.3
*/
public class HostRegistry<T> implements HostValidator<T> {
private static final Logger log = Logger.getLogger(HostRegistry.class.getName());
private final Map<T, Collection<String>> key2HostsMap = new ConcurrentHashMap<>();
private final Map<String, T> host2KeyMap = new ConcurrentHashMap<>();
public T getKeyForHost(String hostName) {
return host2KeyMap.get(hostName);
}
public void update(T key, Collection<String> newHosts) {
verifyHosts(key, newHosts);
log.log(LogLevel.DEBUG, "Setting hosts for key(" + key + "), newHosts(" + newHosts + "), " +
"currentHosts(" + getCurrentHosts(key) + ")");
Collection<String> removedHosts = getRemovedHosts(newHosts, getCurrentHosts(key));
removeHosts(removedHosts);
addHosts(key, newHosts);
}
public void verifyHosts(T key, Collection<String> newHosts) {
for (String host : newHosts) {
if (hostAlreadyTaken(host, key)) {
throw new IllegalArgumentException("'" + key + "' tried to allocate host '" + host +
"', but the host is already taken by '" + host2KeyMap.get(host) + "'");
}
}
}
public void removeHostsForKey(T key) {
for (Iterator<Map.Entry<T, Collection<String>>> it = key2HostsMap.entrySet().iterator(); it.hasNext(); ) {
Map.Entry<T, Collection<String>> entry = it.next();
if (entry.getKey().equals(key)) {
Collection<String> hosts = entry.getValue();
it.remove();
removeHosts(hosts);
}
}
}
public Collection<String> getAllHosts() {
return Collections.unmodifiableCollection(new ArrayList<>(host2KeyMap.keySet()));
}
Collection<String> getCurrentHosts(T key) {
return key2HostsMap.containsKey(key) ? new ArrayList<>(key2HostsMap.get(key)) : new ArrayList<String>();
}
private boolean hostAlreadyTaken(String host, T key) {
return host2KeyMap.containsKey(host) && !key.equals(host2KeyMap.get(host));
}
private static Collection<String> getRemovedHosts(final Collection<String> newHosts, Collection<String> previousHosts) {
return Collections2.filter(previousHosts, new Predicate<String>() {
@Override
public boolean apply(String host) {
return !newHosts.contains(host);
}
});
}
private void removeHosts(Collection<String> removedHosts) {
for (String host : removedHosts) {
log.log(LogLevel.DEBUG, "Removing " + host);
host2KeyMap.remove(host);
}
}
private void addHosts(T key, Collection<String> newHosts) {
for (String host : newHosts) {
log.log(LogLevel.DEBUG, "Adding " + host);
host2KeyMap.put(host, key);
}
key2HostsMap.put(key, new ArrayList<>(newHosts));
}
}
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