/*
* 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.utils;
import java.nio.ByteBuffer;
import java.util.List;
import java.util.concurrent.atomic.AtomicReference;
import java.util.concurrent.CopyOnWriteArrayList;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import com.google.common.base.Objects;
import org.apache.cassandra.db.CounterColumn;
import org.apache.cassandra.db.SystemKeyspace;
public class CounterId implements Comparable<CounterId>
{
private static final Logger logger = LoggerFactory.getLogger(CounterId.class);
public static final int LENGTH = 16; // we assume a fixed length size for all CounterIds
// Lazy holder because this opens the system keyspace and we want to avoid
// having this triggered during class initialization
private static class LocalIds
{
static final LocalCounterIdHistory instance = new LocalCounterIdHistory();
}
private final ByteBuffer id;
private static LocalCounterIdHistory localIds()
{
return LocalIds.instance;
}
public static CounterId getLocalId()
{
return localIds().current.get();
}
/**
* Renew the local counter id.
* To use only when this strictly necessary, as using this will make all
* counter context grow with time.
*/
public static void renewLocalId()
{
renewLocalId(FBUtilities.timestampMicros());
}
public static synchronized void renewLocalId(long now)
{
localIds().renewCurrent(now);
}
/**
* Return the list of old local counter id of this node.
* It is guaranteed that the returned list is sorted by growing counter id
* (and hence the first item will be the oldest counter id for this host)
*/
public static List<CounterIdRecord> getOldLocalCounterIds()
{
return localIds().olds;
}
/**
* Function for test purposes, do not use otherwise.
* Pack an int in a valid CounterId so that the resulting ids respects the
* numerical ordering. Used for creating handcrafted but easy to
* understand contexts in unit tests (see CounterContextTest).
*/
public static CounterId fromInt(int n)
{
long lowBits = 0xC000000000000000L | n;
return new CounterId(ByteBuffer.allocate(16).putLong(0, 0).putLong(8, lowBits));
}
/*
* For performance reasons, this function interns the provided ByteBuffer.
*/
public static CounterId wrap(ByteBuffer id)
{
return new CounterId(id);
}
public static CounterId wrap(ByteBuffer bb, int offset)
{
ByteBuffer dup = bb.duplicate();
dup.position(offset);
dup.limit(dup.position() + LENGTH);
return wrap(dup);
}
private CounterId(ByteBuffer id)
{
if (id.remaining() != LENGTH)
throw new IllegalArgumentException("A CounterId representation is exactly " + LENGTH + " bytes");
this.id = id;
}
public static CounterId generate()
{
return new CounterId(ByteBuffer.wrap(UUIDGen.getTimeUUIDBytes()));
}
/*
* For performance reasons, this function returns a reference to the internal ByteBuffer. Clients not modify the
* result of this function.
*/
public ByteBuffer bytes()
{
return id;
}
public boolean isLocalId()
{
return equals(getLocalId());
}
public int compareTo(CounterId o)
{
return ByteBufferUtil.compareSubArrays(id, id.position(), o.id, o.id.position(), CounterId.LENGTH);
}
@Override
public String toString()
{
return UUIDGen.getUUID(id).toString();
}
@Override
public boolean equals(Object o)
{
if (this == o)
return true;
if (o == null || getClass() != o.getClass())
return false;
CounterId otherId = (CounterId)o;
return id.equals(otherId.id);
}
@Override
public int hashCode()
{
return id.hashCode();
}
public static class OneShotRenewer
{
private boolean renewed;
private final CounterId initialId;
public OneShotRenewer()
{
renewed = false;
initialId = getLocalId();
}
public void maybeRenew(CounterColumn column)
{
if (!renewed && column.hasCounterId(initialId))
{
renewLocalId();
renewed = true;
}
}
}
private static class LocalCounterIdHistory
{
private final AtomicReference<CounterId> current;
private final List<CounterIdRecord> olds;
LocalCounterIdHistory()
{
CounterId id = SystemKeyspace.getCurrentLocalCounterId();
if (id == null)
{
// no recorded local counter id, generating a new one and saving it
id = generate();
logger.info("No saved local counter id, using newly generated: {}", id);
SystemKeyspace.writeCurrentLocalCounterId(id, FBUtilities.timestampMicros());
current = new AtomicReference<>(id);
olds = new CopyOnWriteArrayList<>();
}
else
{
logger.info("Saved local counter id: {}", id);
current = new AtomicReference<>(id);
olds = new CopyOnWriteArrayList<>(SystemKeyspace.getOldLocalCounterIds());
}
}
synchronized void renewCurrent(long now)
{
CounterId newCounterId = generate();
CounterId old = current.get();
SystemKeyspace.writeCurrentLocalCounterId(newCounterId, now);
current.set(newCounterId);
olds.add(new CounterIdRecord(old, now));
}
}
public static class CounterIdRecord
{
public final CounterId id;
public final long timestamp;
public CounterIdRecord(CounterId id, long timestamp)
{
this.id = id;
this.timestamp = timestamp;
}
@Override
public boolean equals(Object o)
{
if (this == o)
return true;
if (o == null || getClass() != o.getClass())
return false;
CounterIdRecord otherRecord = (CounterIdRecord)o;
return id.equals(otherRecord.id) && timestamp == otherRecord.timestamp;
}
@Override
public int hashCode()
{
return Objects.hashCode(id, timestamp);
}
public String toString()
{
return String.format("(%s, %d)", id.toString(), timestamp);
}
}
}