1 /***********************************************************************
2  * Copyright (c) 2013-2024 Commonwealth Computer Research, Inc.
3  * All rights reserved. This program and the accompanying materials
4  * are made available under the terms of the Apache License, Version 2.0
5  * which accompanies this distribution and is available at
6  * http://www.opensource.org/licenses/apache2.0.php.
7  ***********************************************************************/
8 
9 package org.locationtech.geomesa.utils.uuid
10 
11 import org.geotools.api.feature.simple.{SimpleFeature, SimpleFeatureType}
12 import org.locationtech.geomesa.utils.index.ByteArrays
13 
14 import java.util.UUID
15 
16 /**
17  * Creates feature id based on current system time.
18  */
19 class IngestTimeFeatureIdGenerator extends FeatureIdGenerator {
20   override def createId(sft: SimpleFeatureType, sf: SimpleFeature): String =
21     TimeSortedUuidGenerator.createUuid().toString
22 }
23 
24 /**
25  * UUID generator that creates UUIDs that sort by creation time (useful for accumulo).
26  *
27  * Uses variant 2 (IETF) and version 4 (for random UUIDs, although it's not totally random).
28  * See https://en.wikipedia.org/wiki/Universally_unique_identifier#Variants_and_versions
29  *
30  * Using a version 1 (time based) UUID doesn't ensure uniqueness when running in different processes on
31  * the same machine (at least not without some complicated distributed locking), as MAC address
32  * (or IP address) is the unique factor.
33  */
34 object TimeSortedUuidGenerator extends RandomLsbUuidGenerator {
35 
36   /**
37    * Creates a UUID where the first 8 bytes are based on the current time and the second 8 bytes are
38    * based on a random number. This should provide uniqueness along with sorting by date.
39    *
40    * Doesn't support negative time values.
41    */
42   def createUuid(time: Long = System.currentTimeMillis()): UUID = {
43     val mostSigBits = timeBytes(time)
44     val leastSigBits = createRandomLsb()
45     new UUID(mostSigBits, leastSigBits)
46   }
47 
48   /**
49    * Creates the time based part of the uuid.
50    */
51   private def timeBytes(time: Long): Long = {
52     val array = getTempByteArray
53 
54     // write the time in a sorted fashion
55     // we drop the 4 most significant bits as we need 4 bits extra for the version
56     // this shouldn't matter as we use sys time, so we don't need to worry about negative numbers
57     array(0) = (time >> 52).asInstanceOf[Byte]
58     array(1) = (time >> 44).asInstanceOf[Byte]
59     array(2) = (time >> 36).asInstanceOf[Byte]
60     array(3) = (time >> 28).asInstanceOf[Byte]
61     array(4) = (time >> 20).asInstanceOf[Byte]
62     array(5) = (time >> 12).asInstanceOf[Byte]
63     array(6) = ((time >> 8) & 0x0f).asInstanceOf[Byte]  // the 0x0f clears the version bits
64     array(7) = time.asInstanceOf[Byte]
65 
66     // set the version number for the UUID
67     setVersion(array)
68 
69     ByteArrays.readLong(array)
70   }
71 }