/*
* Copyright (C) 2012-2015 DataStax Inc.
*
* 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 com.datastax.driver.core.utils;
import com.datastax.driver.core.Native;
import com.google.common.base.Charsets;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.lang.management.ManagementFactory;
import java.net.InetAddress;
import java.net.NetworkInterface;
import java.net.SocketException;
import java.net.UnknownHostException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.*;
import java.util.concurrent.atomic.AtomicLong;
/**
* Utility methods to help working with UUIDs, and more specifically, with time-based UUIDs
* (also known as Version 1 UUIDs).
* <h3>Notes on the algorithm used to generate time-based UUIDs</h3>
* The algorithm follows roughly the description in RFC-4122, but with the following adaptations:
* <ol>
* <li>Since Java does not provide direct access to the host's MAC address, that information
* is replaced with a digest of all IP addresses available on the host;</li>
* <li>The process ID (PID) isn't easily available to Java either, so it is determined by one of the
* following methods, in the order they are listed below:
* <ol>
* <li>If the System property <code>{@value PID_SYSTEM_PROPERTY}</code> is set then the value to use as a PID
* will be read from that property;</li>
* <li>Otherwise, if a native call to {@link Native#processId() getpid()} is possible, then the PID
* will be read from that call;</li>
* <li>Otherwise, an attempt will be made to read the PID from JMX's
* {@link ManagementFactory#getRuntimeMXBean() RuntimeMXBean}, which is a well-known,
* yet undocumented "hack", since most JVMs tend to use the JVM's PID as part of that MXBean name;</li>
* <li>If all of the above fails, a random integer will be generated and used as a surrogate PID.</li>
* </ol>
* </li>
* </ol>
*
* @see <a href="https://datastax-oss.atlassian.net/browse/JAVA-444">JAVA-444</a>
* @see <a href="http://www.ietf.org/rfc/rfc4122.txt">A Universally Unique IDentifier (UUID) URN Namespace (RFC 4122)</a>
*/
public final class UUIDs {
/**
* The System property to use to force the value of the process ID (PID).
*/
public static final String PID_SYSTEM_PROPERTY = "com.datastax.driver.PID";
private static final Logger LOGGER = LoggerFactory.getLogger(UUIDs.class);
private UUIDs() {
}
private static final long START_EPOCH = makeEpoch();
private static final long CLOCK_SEQ_AND_NODE = makeClockSeqAndNode();
/*
* 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)
* because I don't trust all uuid implementation to have correctly set
* those (pycassa don't always for instance).
*/
private static final long MIN_CLOCK_SEQ_AND_NODE = 0x8080808080808080L;
private static final long MAX_CLOCK_SEQ_AND_NODE = 0x7f7f7f7f7f7f7f7fL;
private static final AtomicLong lastTimestamp = new AtomicLong(0L);
private static long makeEpoch() {
// UUID v1 timestamp must be in 100-nanoseconds interval since 00:00:00.000 15 Oct 1582.
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);
return c.getTimeInMillis();
}
private static long makeNode() {
/*
* We don't have access to the MAC address (in pure JAVA at least) 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 as well as a few
* other sources.
*/
try {
MessageDigest digest = MessageDigest.getInstance("MD5");
for (String address : getAllLocalAddresses())
update(digest, address);
Properties props = System.getProperties();
update(digest, props.getProperty("java.vendor"));
update(digest, props.getProperty("java.vendor.url"));
update(digest, props.getProperty("java.version"));
update(digest, props.getProperty("os.arch"));
update(digest, props.getProperty("os.name"));
update(digest, props.getProperty("os.version"));
update(digest, getProcessPiece());
byte[] hash = digest.digest();
long node = 0;
for (int i = 0; i < 6; i++)
node |= (0x00000000000000ffL & (long) hash[i]) << (i * 8);
// Since we don't use the mac address, the spec says that multicast
// bit (least significant bit of the first byte of the node ID) must be 1.
return node | 0x0000010000000000L;
} catch (NoSuchAlgorithmException e) {
throw new RuntimeException(e);
}
}
private static String getProcessPiece() {
Integer pid = null;
String pidProperty = System.getProperty(PID_SYSTEM_PROPERTY);
if (pidProperty != null) {
try {
pid = Integer.parseInt(pidProperty);
LOGGER.info("PID obtained from System property {}: {}", PID_SYSTEM_PROPERTY, pid);
} catch (NumberFormatException e) {
LOGGER.warn("Incorrect integer specified for PID in System property {}: {}", PID_SYSTEM_PROPERTY, pidProperty);
}
}
if (pid == null && Native.isGetpidAvailable()) {
try {
pid = Native.processId();
LOGGER.info("PID obtained through native call to getpid(): {}", pid);
} catch (Exception e) {
LOGGER.warn("Native call to getpid() failed", e);
}
}
if (pid == null) {
try {
String pidJmx = ManagementFactory.getRuntimeMXBean().getName().split("@")[0];
pid = Integer.parseInt(pidJmx);
LOGGER.info("PID obtained through JMX: {}", pid);
} catch (Exception e) {
LOGGER.warn("Failed to obtain PID from JMX", e);
}
}
if (pid == null) {
pid = new java.util.Random().nextInt();
LOGGER.warn("Could not determine PID, falling back to a random integer: {}", pid);
}
ClassLoader loader = UUIDs.class.getClassLoader();
int loaderId = loader != null ? System.identityHashCode(loader) : 0;
return Integer.toHexString(pid) + Integer.toHexString(loaderId);
}
private static void update(MessageDigest digest, String value) {
if (value != null)
digest.update(value.getBytes(Charsets.UTF_8));
}
private static long makeClockSeqAndNode() {
long clock = new Random(System.currentTimeMillis()).nextLong();
long node = makeNode();
long lsb = 0;
lsb |= (clock & 0x0000000000003FFFL) << 48;
lsb |= 0x8000000000000000L;
lsb |= node;
return lsb;
}
/**
* Creates a new random (version 4) UUID.
* <p/>
* This method is just a convenience for {@code UUID.randomUUID()}.
*
* @return a newly generated, pseudo random, version 4 UUID.
*/
public static UUID random() {
return UUID.randomUUID();
}
/**
* Creates a new time-based (version 1) UUID.
* <p/>
* UUIDs generated by this method are suitable for use with the
* {@code timeuuid} Cassandra type. In particular the generated UUID
* includes the timestamp of its generation.
* <p/>
* Note that there is no way to provide your own timestamp. This is deliberate, as we feel that this does not
* conform to the UUID specification, and therefore don't want to encourage it through the API.
* If you want to do it anyway, use the following workaround:
* <pre>
* Random random = new Random();
* UUID uuid = new UUID(UUIDs.startOf(userProvidedTimestamp).getMostSignificantBits(), random.nextLong());
* </pre>
* If you simply need to perform a range query on a {@code timeuuid} column, use the "fake" UUID generated by
* {@link #startOf(long)} and {@link #endOf(long)}.
*
* @return a new time-based UUID.
*/
public static UUID timeBased() {
return new UUID(makeMSB(getCurrentTimestamp()), CLOCK_SEQ_AND_NODE);
}
/**
* Creates a "fake" time-based UUID that sorts as the smallest possible
* version 1 UUID generated at the provided timestamp.
* <p/>
* Such created UUIDs are useful in queries to select a time range of a
* {@code timeuuid} column.
* <p/>
* The UUIDs created by this method <b>are not unique</b> and as such are
* <b>not</b> suitable for anything else than querying a specific time
* range. In particular, you should not insert such UUIDs. "True" UUIDs from
* user-provided timestamps are not supported (see {@link #timeBased()}
* for more explanations).
* <p/>
* Also, the timestamp to provide as a parameter must be a Unix timestamp (as
* returned by {@link System#currentTimeMillis} or {@link java.util.Date#getTime}), and
* <em>not</em> a count of 100-nanosecond intervals since 00:00:00.00, 15 October 1582 (as required by RFC-4122).
* <p/>
* In other words, given a UUID {@code uuid}, you should never call
* {@code startOf(uuid.timestamp())} but rather
* {@code startOf(unixTimestamp(uuid))}.
* <p/>
* Lastly, please note that Cassandra's {@code timeuuid} sorting is not compatible
* with {@link UUID#compareTo} and hence the UUIDs created by this method
* are not necessarily lower bound for that latter method.
*
* @param timestamp the Unix timestamp for which the created UUID must be a
* lower bound.
* @return the smallest (for Cassandra {@code timeuuid} sorting) UUID of {@code timestamp}.
*/
public static UUID startOf(long timestamp) {
return new UUID(makeMSB(fromUnixTimestamp(timestamp)), MIN_CLOCK_SEQ_AND_NODE);
}
/**
* Creates a "fake" time-based UUID that sorts as the biggest possible
* version 1 UUID generated at the provided timestamp.
* <p/>
* See {@link #startOf(long)} for explanations about the intended usage of such UUID.
*
* @param timestamp the Unix timestamp for which the created UUID must be an
* upper bound.
* @return the biggest (for Cassandra {@code timeuuid} sorting) UUID of {@code timestamp}.
*/
public static UUID endOf(long timestamp) {
long uuidTstamp = fromUnixTimestamp(timestamp + 1) - 1;
return new UUID(makeMSB(uuidTstamp), MAX_CLOCK_SEQ_AND_NODE);
}
/**
* Return the Unix timestamp contained by the provided time-based UUID.
* <p/>
* This method is not equivalent to {@link UUID#timestamp()}. More
* precisely, a version 1 UUID stores a timestamp that represents the
* number of 100-nanoseconds intervals since midnight, 15 October 1582 and
* that is what {@link UUID#timestamp()} returns. This method however
* converts that timestamp to the equivalent Unix timestamp in
* milliseconds, i.e. a timestamp representing a number of milliseconds
* since midnight, January 1, 1970 UTC. In particular, the timestamps
* returned by this method are comparable to the timestamps returned by
* {@link System#currentTimeMillis}, {@link java.util.Date#getTime}, etc.
*
* @param uuid the UUID to return the timestamp of.
* @return the Unix timestamp of {@code uuid}.
* @throws IllegalArgumentException if {@code uuid} is not a version 1 UUID.
*/
public static long unixTimestamp(UUID uuid) {
if (uuid.version() != 1)
throw new IllegalArgumentException(String.format("Can only retrieve the unix timestamp for version 1 uuid (provided version %d)", uuid.version()));
long timestamp = uuid.timestamp();
return (timestamp / 10000) + START_EPOCH;
}
/*
* Note that currently we use {@link System#currentTimeMillis} for a base time in
* milliseconds, and then if we are in the same milliseconds that the
* previous generation, we increment the number of nanoseconds.
* However, since the precision is 100-nanoseconds intervals, we can only
* generate 10K UUID within a millisecond safely. If we detect we have
* already generated that much UUID within a millisecond (which, while
* admittedly unlikely in a real application, is very achievable on even
* modest machines), then we stall the generator (busy spin) until the next
* millisecond as required by the RFC.
*/
private static long getCurrentTimestamp() {
while (true) {
long now = fromUnixTimestamp(System.currentTimeMillis());
long last = lastTimestamp.get();
if (now > last) {
if (lastTimestamp.compareAndSet(last, now))
return now;
} else {
long lastMillis = millisOf(last);
// If the clock went back in time, bail out
if (millisOf(now) < millisOf(last))
return lastTimestamp.incrementAndGet();
long candidate = last + 1;
// If we've generated more than 10k uuid in that millisecond,
// we restart the whole process until we get to the next millis.
// Otherwise, we try use our candidate ... unless we've been
// beaten by another thread in which case we try again.
if (millisOf(candidate) == lastMillis && lastTimestamp.compareAndSet(last, candidate))
return candidate;
}
}
}
// Package visible for testing
static long fromUnixTimestamp(long tstamp) {
return (tstamp - START_EPOCH) * 10000;
}
private static long millisOf(long timestamp) {
return timestamp / 10000;
}
// Package visible for testing
static long makeMSB(long timestamp) {
long msb = 0L;
msb |= (0x00000000ffffffffL & timestamp) << 32;
msb |= (0x0000ffff00000000L & timestamp) >>> 16;
msb |= (0x0fff000000000000L & timestamp) >>> 48;
msb |= 0x0000000000001000L; // sets the version to 1.
return msb;
}
private static Set<String> getAllLocalAddresses() {
Set<String> allIps = new HashSet<String>();
try {
InetAddress localhost = InetAddress.getLocalHost();
allIps.add(localhost.toString());
// Also return the hostname if available, it won't hurt (this does a dns lookup, it's only done once at startup)
allIps.add(localhost.getCanonicalHostName());
InetAddress[] allMyIps = InetAddress.getAllByName(localhost.getCanonicalHostName());
if (allMyIps != null) {
for (int i = 0; i < allMyIps.length; i++)
allIps.add(allMyIps[i].toString());
}
} catch (UnknownHostException e) {
// Ignore, we'll try the network interfaces anyway
}
try {
Enumeration<NetworkInterface> en = NetworkInterface.getNetworkInterfaces();
if (en != null) {
while (en.hasMoreElements()) {
Enumeration<InetAddress> enumIpAddr = en.nextElement().getInetAddresses();
while (enumIpAddr.hasMoreElements())
allIps.add(enumIpAddr.nextElement().toString());
}
}
} catch (SocketException e) {
// Ignore, if we've really got nothing so far, we'll throw an exception
}
return allIps;
}
}