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The Apache Cassandra Project develops a highly scalable second-generation distributed database, bringing together Dynamo's fully distributed design and Bigtable's ColumnFamily-based data model.
/*
* 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.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.io.Serializable;
import java.net.InetAddress;
import java.net.NetworkInterface;
import java.net.SocketException;
import java.nio.ByteBuffer;
import java.security.SecureRandom;
import java.util.Collection;
import java.util.Collections;
import java.util.Enumeration;
import java.util.HashSet;
import java.util.List;
import java.util.Random;
import java.util.Set;
import java.util.UUID;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicLong;
import java.util.function.Function;
import java.util.stream.Collectors;
import com.google.common.hash.Hasher;
import com.google.common.hash.Hashing;
import org.apache.cassandra.config.DatabaseDescriptor;
import org.apache.cassandra.db.marshal.ValueAccessor;
import org.apache.cassandra.io.IVersionedSerializer;
import org.apache.cassandra.io.util.DataInputPlus;
import org.apache.cassandra.io.util.DataOutputPlus;
import org.apache.cassandra.locator.InetAddressAndPort;
import org.apache.cassandra.serializers.MarshalException;
import org.apache.cassandra.serializers.TypeSerializer;
import static java.util.concurrent.TimeUnit.MICROSECONDS;
import static org.apache.cassandra.config.CassandraRelevantProperties.CASSANDRA_UNSAFE_TIME_UUID_NODE;
import static org.apache.cassandra.config.CassandraRelevantProperties.DETERMINISM_UNSAFE_UUID_NODE;
import static org.apache.cassandra.utils.ByteBufferUtil.EMPTY_BYTE_BUFFER;
import static org.apache.cassandra.utils.Clock.Global.currentTimeMillis;
import static org.apache.cassandra.utils.Shared.Recursive.INTERFACES;
@Shared(inner = INTERFACES)
public class TimeUUID implements Serializable, Comparable
{
public static final long serialVersionUID = 1L;
// A grand day! millis at 00:00:00.000 15 Oct 1582.
public static final long UUID_EPOCH_UNIX_MILLIS = -12219292800000L;
protected static final long TIMESTAMP_UUID_VERSION_IN_MSB = 0x1000L;
protected static final long UUID_VERSION_BITS_IN_MSB = 0xf000L;
/*
* The min and max possible lsb for a UUID.
* Note that his is not 0 and all 1's because Cassandra TimeUUIDType
* compares the lsb parts as a signed byte array comparison. So the min
* value is 8 times -128 and the max is 8 times +127.
*
* Note that we ignore the uuid variant (namely, MIN_CLOCK_SEQ_AND_NODE
* have variant 2 as it should, but MAX_CLOCK_SEQ_AND_NODE have variant 0).
* I don't think that has any practical consequence and is more robust in
* case someone provides a UUID with a broken variant.
*/
private static final long MIN_CLOCK_SEQ_AND_NODE = 0x8080808080808080L;
private static final long MAX_CLOCK_SEQ_AND_NODE = 0x7f7f7f7f7f7f7f7fL;
public static final long TIMEUUID_SIZE = ObjectSizes.measureDeep(new TimeUUID(10, 10));
final long uuidTimestamp, lsb;
public TimeUUID(long uuidTimestamp, long lsb)
{
// we don't validate that this is a true TIMEUUID to avoid problems with historical mixing of UUID with TimeUUID
this.uuidTimestamp = uuidTimestamp;
this.lsb = lsb;
}
public static TimeUUID atUnixMicrosWithLsb(long unixMicros, long uniqueLsb)
{
return new TimeUUID(unixMicrosToRawTimestamp(unixMicros), uniqueLsb);
}
public static UUID atUnixMicrosWithLsbAsUUID(long unixMicros, long uniqueLsb)
{
return new UUID(rawTimestampToMsb(unixMicrosToRawTimestamp(unixMicros)), uniqueLsb);
}
/**
* Returns the smaller possible type 1 UUID having the provided timestamp.
*
* Warning: this method should only be used for querying as this
* doesn't at all guarantee the uniqueness of the resulting UUID.
*/
public static TimeUUID minAtUnixMillis(long unixMillis)
{
return new TimeUUID(unixMillisToRawTimestamp(unixMillis, 0), MIN_CLOCK_SEQ_AND_NODE);
}
/**
* Returns the biggest possible type 1 UUID having the provided timestamp.
*
* Warning: this method should only be used for querying as this
* doesn't at all guarantee the uniqueness of the resulting UUID.
*/
public static TimeUUID maxAtUnixMillis(long unixMillis)
{
return new TimeUUID(unixMillisToRawTimestamp(unixMillis + 1, 0) - 1, MAX_CLOCK_SEQ_AND_NODE);
}
public static TimeUUID fromString(String uuidString)
{
return fromUuid(UUID.fromString(uuidString));
}
public static TimeUUID fromUuid(UUID uuid)
{
return fromBytes(uuid.getMostSignificantBits(), uuid.getLeastSignificantBits());
}
public static TimeUUID fromBytes(long msb, long lsb)
{
return new TimeUUID(msbToRawTimestamp(msb), lsb);
}
public static TimeUUID deserialize(ByteBuffer buffer)
{
return fromBytes(buffer.getLong(buffer.position()), buffer.getLong(buffer.position() + 8));
}
public static TimeUUID deserialize(DataInput in) throws IOException
{
long msb = in.readLong();
long lsb = in.readLong();
return fromBytes(msb, lsb);
}
public void serialize(DataOutput out) throws IOException
{
out.writeLong(msb());
out.writeLong(lsb());
}
public ByteBuffer toBytes()
{
return ByteBuffer.wrap(toBytes(msb(), lsb()));
}
public static byte[] toBytes(long msb, long lsb)
{
byte[] uuidBytes = new byte[16];
for (int i = 0; i < 8; i++)
uuidBytes[i] = (byte) (msb >>> 8 * (7 - i));
for (int i = 8; i < 16; i++)
uuidBytes[i] = (byte) (lsb >>> 8 * (15 - i));
return uuidBytes;
}
public static long sizeInBytes()
{
return 16;
}
public UUID asUUID()
{
return new UUID(rawTimestampToMsb(uuidTimestamp), lsb);
}
/**
* The Cassandra internal micros-resolution timestamp of the TimeUUID, as of unix epoch
*/
public long unix(TimeUnit units)
{
return units.convert(unixMicros(), MICROSECONDS);
}
/**
* The Cassandra internal micros-resolution timestamp of the TimeUUID, as of unix epoch
*/
public long unixMicros()
{
return rawTimestampToUnixMicros(uuidTimestamp);
}
/**
* The UUID-format timestamp, i.e. 10x micros-resolution, as of UUIDGen.UUID_EPOCH_UNIX_MILLIS
* The tenths of a microsecond are used to store a flag value.
*/
public long uuidTimestamp()
{
return uuidTimestamp & 0x0FFFFFFFFFFFFFFFL;
}
public long msb()
{
return rawTimestampToMsb(uuidTimestamp);
}
public long lsb()
{
return lsb;
}
public static long rawTimestampToUnixMicros(long rawTimestamp)
{
return (rawTimestamp / 10) + UUID_EPOCH_UNIX_MILLIS * 1000;
}
public static long unixMillisToRawTimestamp(long unixMillis, long tenthsOfAMicro)
{
return unixMillis * 10000 - (UUID_EPOCH_UNIX_MILLIS * 10000) + tenthsOfAMicro;
}
public static long unixMicrosToRawTimestamp(long unixMicros)
{
return unixMicros * 10 - (UUID_EPOCH_UNIX_MILLIS * 10000);
}
public static long msbToRawTimestamp(long msb)
{
assert (UUID_VERSION_BITS_IN_MSB & msb) == TIMESTAMP_UUID_VERSION_IN_MSB;
msb &= ~TIMESTAMP_UUID_VERSION_IN_MSB;
return (msb & 0xFFFFL) << 48
| (msb & 0xFFFF0000L) << 16
| (msb >>> 32);
}
public static long rawTimestampToMsb(long rawTimestamp)
{
return TIMESTAMP_UUID_VERSION_IN_MSB
| (rawTimestamp >>> 48)
| ((rawTimestamp & 0xFFFF00000000L) >>> 16)
| (rawTimestamp << 32);
}
@Override
public int hashCode()
{
return (int) ((uuidTimestamp ^ (uuidTimestamp >> 32) * 31) + (lsb ^ (lsb >> 32)));
}
@Override
public boolean equals(Object that)
{
return (that instanceof UUID && equals((UUID) that))
|| (that instanceof TimeUUID && equals((TimeUUID) that));
}
public boolean equals(TimeUUID that)
{
return that != null && uuidTimestamp == that.uuidTimestamp && lsb == that.lsb;
}
public boolean equals(UUID that)
{
return that != null && uuidTimestamp == that.timestamp() && lsb == that.getLeastSignificantBits();
}
@Override
public String toString()
{
return asUUID().toString();
}
public static String toString(TimeUUID ballot)
{
return ballot == null ? "null" : ballot.uuidTimestamp() + ":" + ballot;
}
public static String toString(TimeUUID ballot, String kind)
{
return ballot == null ? "null" : String.format("%s(%d:%s)", kind, ballot.uuidTimestamp(), ballot);
}
@Override
public int compareTo(TimeUUID that)
{
return this.uuidTimestamp != that.uuidTimestamp
? Long.compare(this.uuidTimestamp, that.uuidTimestamp)
: Long.compare(this.lsb, that.lsb);
}
protected static abstract class AbstractSerializer extends TypeSerializer
{
public void validate(V value, ValueAccessor accessor) throws MarshalException
{
if (accessor.isEmpty(value))
return;
if (accessor.size(value) != 16)
throw new MarshalException(String.format("UUID should be 16 or 0 bytes (%d)", accessor.size(value)));
if ((accessor.getByte(value, 6) & 0xf0) != 0x10)
throw new MarshalException(String.format("Invalid version for TimeUUID type: 0x%s", Integer.toHexString((accessor.getByte(value, 0) >> 4) & 0xf)));
}
public String toString(T value)
{
return value == null ? "" : value.toString();
}
public ByteBuffer serialize(T value)
{
if (value == null)
return EMPTY_BYTE_BUFFER;
ByteBuffer buffer = ByteBuffer.allocate(16);
buffer.putLong(value.msb());
buffer.putLong(value.lsb());
buffer.flip();
return buffer;
}
}
public static class Serializer extends AbstractSerializer implements IVersionedSerializer
{
public static final Serializer instance = new Serializer();
public TimeUUID deserialize(V value, ValueAccessor accessor)
{
return accessor.isEmpty(value) ? null : accessor.toTimeUUID(value);
}
public Class getType()
{
return TimeUUID.class;
}
@Override
public void serialize(TimeUUID t, DataOutputPlus out, int version) throws IOException
{
t.serialize(out);
}
@Override
public TimeUUID deserialize(DataInputPlus in, int version) throws IOException
{
return TimeUUID.deserialize(in);
}
@Override
public long serializedSize(TimeUUID t, int version)
{
return 16;
}
}
public static class Generator
{
private static final long clockSeqAndNode = makeClockSeqAndNode();
private static final AtomicLong lastMicros = new AtomicLong();
public static TimeUUID nextTimeUUID()
{
return atUnixMicrosWithLsb(nextUnixMicros(), clockSeqAndNode);
}
public static UUID nextTimeAsUUID()
{
return atUnixMicrosWithLsbAsUUID(nextUnixMicros(), clockSeqAndNode);
}
public static TimeUUID atUnixMillis(long unixMillis)
{
return atUnixMillis(unixMillis, 0);
}
public static TimeUUID atUnixMillis(long unixMillis, long tenthsOfAMicro)
{
return new TimeUUID(unixMillisToRawTimestamp(unixMillis, tenthsOfAMicro), clockSeqAndNode);
}
public static byte[] atUnixMillisAsBytes(long unixMillis)
{
return atUnixMillisAsBytes(unixMillis, 0);
}
public static byte[] atUnixMillisAsBytes(long unixMillis, long tenthsOfAMicro)
{
return toBytes(rawTimestampToMsb(unixMillisToRawTimestamp(unixMillis, tenthsOfAMicro)), clockSeqAndNode);
}
public static byte[] nextTimeUUIDAsBytes()
{
return toBytes(rawTimestampToMsb(unixMicrosToRawTimestamp(nextUnixMicros())), clockSeqAndNode);
}
// needs to return two different values for the same when.
// we can generate at most 10k UUIDs per ms.
private static long nextUnixMicros()
{
long newLastMicros;
while (true)
{
//Generate a candidate value for new lastNanos
newLastMicros = currentTimeMillis() * 1000;
long originalLastNanos = lastMicros.get();
if (newLastMicros > originalLastNanos)
{
//Slow path once per millisecond do a CAS
if (lastMicros.compareAndSet(originalLastNanos, newLastMicros))
{
break;
}
}
else
{
//Fast path do an atomic increment
//Or when falling behind this will move time forward past the clock if necessary
newLastMicros = lastMicros.incrementAndGet();
break;
}
}
return newLastMicros;
}
private static long makeClockSeqAndNode()
{
if (DETERMINISM_UNSAFE_UUID_NODE.getBoolean())
return FBUtilities.getBroadcastAddressAndPort().addressBytes[3];
if (CASSANDRA_UNSAFE_TIME_UUID_NODE.isPresent())
return CASSANDRA_UNSAFE_TIME_UUID_NODE.getLong()
^ FBUtilities.getBroadcastAddressAndPort().addressBytes[3]
^ (FBUtilities.getBroadcastAddressAndPort().addressBytes[2] << 8);
long clock = new SecureRandom().nextLong();
long lsb = 0;
lsb |= 0x8000000000000000L; // variant (2 bits)
lsb |= (clock & 0x0000000000003FFFL) << 48; // clock sequence (14 bits)
lsb |= makeNode(); // 6 bytes
return lsb;
}
private static long makeNode()
{
/*
* We don't have access to the MAC address but need to generate a node part
* that identify this host as uniquely as possible.
* The spec says that one option is to take as many source that identify
* this node as possible and hash them together. That's what we do here by
* gathering all the ip of this host.
* Note that FBUtilities.getJustBroadcastAddress() should be enough to uniquely
* identify the node *in the cluster* but it triggers DatabaseDescriptor
* instanciation and the UUID generator is used in Stress for instance,
* where we don't want to require the yaml.
*/
Collection localAddresses = getAllLocalAddresses();
if (localAddresses.isEmpty())
throw new RuntimeException("Cannot generate the node component of the UUID because cannot retrieve any IP addresses.");
// ideally, we'd use the MAC address, but java doesn't expose that.
byte[] hash = hash(localAddresses);
long node = 0;
for (int i = 0; i < Math.min(6, hash.length); i++)
node |= (0x00000000000000ff & (long)hash[i]) << (5-i)*8;
assert (0xff00000000000000L & node) == 0;
// Since we don't use the mac address, the spec says that multicast
// bit (least significant bit of the first octet of the node ID) must be 1.
return node | 0x0000010000000000L;
}
private static byte[] hash(Collection data)
{
// Identify the host.
Hasher hasher = Hashing.md5().newHasher();
for(InetAddressAndPort addr : data)
{
hasher.putBytes(addr.addressBytes);
hasher.putInt(addr.getPort());
}
// Identify the process on the load: we use both the PID and class loader hash.
long pid = NativeLibrary.getProcessID();
if (pid < 0)
pid = new Random(currentTimeMillis()).nextLong();
updateWithLong(hasher, pid);
ClassLoader loader = UUIDGen.class.getClassLoader();
int loaderId = loader != null ? System.identityHashCode(loader) : 0;
updateWithInt(hasher, loaderId);
return hasher.hash().asBytes();
}
private static void updateWithInt(Hasher hasher, int val)
{
hasher.putByte((byte) ((val >>> 24) & 0xFF));
hasher.putByte((byte) ((val >>> 16) & 0xFF));
hasher.putByte((byte) ((val >>> 8) & 0xFF));
hasher.putByte((byte) ((val >>> 0) & 0xFF));
}
public static void updateWithLong(Hasher hasher, long val)
{
hasher.putByte((byte) ((val >>> 56) & 0xFF));
hasher.putByte((byte) ((val >>> 48) & 0xFF));
hasher.putByte((byte) ((val >>> 40) & 0xFF));
hasher.putByte((byte) ((val >>> 32) & 0xFF));
hasher.putByte((byte) ((val >>> 24) & 0xFF));
hasher.putByte((byte) ((val >>> 16) & 0xFF));
hasher.putByte((byte) ((val >>> 8) & 0xFF));
hasher.putByte((byte) ((val >>> 0) & 0xFF));
}
/**
* Helper function used exclusively by UUIDGen to create
**/
public static Collection getAllLocalAddresses()
{
Set localAddresses = new HashSet<>();
try
{
Enumeration nets = NetworkInterface.getNetworkInterfaces();
if (nets != null)
{
while (nets.hasMoreElements())
{
Function converter =
address -> InetAddressAndPort.getByAddressOverrideDefaults(address, 0);
List addresses =
Collections.list(nets.nextElement().getInetAddresses()).stream().map(converter).collect(Collectors.toList());
localAddresses.addAll(addresses);
}
}
}
catch (SocketException e)
{
throw new AssertionError(e);
}
if (DatabaseDescriptor.isDaemonInitialized())
{
localAddresses.add(FBUtilities.getBroadcastAddressAndPort());
localAddresses.add(FBUtilities.getBroadcastNativeAddressAndPort());
localAddresses.add(FBUtilities.getLocalAddressAndPort());
}
return localAddresses;
}
}
}
// ---Copied from UUIDGen
// for the curious, here is how I generated START_EPOCH
// Calendar c = Calendar.getInstance(TimeZone.getTimeZone("GMT-0"));
// c.set(Calendar.YEAR, 1582);
// c.set(Calendar.MONTH, Calendar.OCTOBER);
// c.set(Calendar.DAY_OF_MONTH, 15);
// c.set(Calendar.HOUR_OF_DAY, 0);
// c.set(Calendar.MINUTE, 0);
// c.set(Calendar.SECOND, 0);
// c.set(Calendar.MILLISECOND, 0);
// long START_EPOCH = c.getTimeInMillis();
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