301 |
302 |
303 |
304 |
305 |
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/LICENSE:
--------------------------------------------------------------------------------
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/README.md:
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1 | # Distributed Id Generation
2 |
3 | What is the need to generate a unique identifier?
4 |
5 | We as part of day to day operation do capture occurrences of events and persist them in data stores. Each of these entries has to be identified uniquely. This is where we use identifiers to identify them. The identifiers that are used to identify the record uniquely may be of numeric type or string type.
6 |
7 | The requirement is to create ids which is roughly sorted by time and can be used across products i.e the same id generator should be used across domains. Consider a retail example the same id generator should be used for order, stock, price, payment, shipment, notification etc. The id generation should be fast and should generate unique and should not have single point of failures.
8 |
9 | In this tutorial we are going to look in to ways to create these identifiers in different use cases.
10 |
11 | 1. Create id in database.
12 | 2. Create id from backend and send to database.
13 |
14 | ## UUIDs
15 |
16 | UUID - universally unique id or GUID by microsoft is a 128 bit id used to generate ids which can be generated in distributed manner and still remain unique. This uniqueness does not depend on central co-ordination between the systems creating them. So the defacto choice for many people creating unique identifiers are UUIDs. The possibility of duplication even when created in distributed manner is close to zero. Since the possible values are 2 to the power of 128 the max values is 340,282,366,920,938,463,463,374,607,431,768,211,456.
17 |
18 | Sample UUID - xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx
19 | 907f39b0-6778-**4**c47-b173-e6348efa1641
20 | M is the UUID version here we are using type 4 UUIDs
21 | N is the UUID variant
22 |
23 | The default UUIDs that we create out of syntax.
24 | ```
25 | UUID.randomUUID() is version 4 UUID
26 | ```
27 |
28 | What are the pros and cons of UUIDs to uniquely identify records?
29 |
30 | Easy to generate.
31 | Fast.
32 | Uniquness.
33 | Random i.e. we cannot predict next id with the current id.
34 |
35 | UUIDs are 128 bits long which is 32 chars in length.
36 | Sorting UUIDs would not result in ordering of actual records since they are random and not generated in any sequence.
37 |
38 | ## Auto incrementing Ids - Identity columns
39 |
40 | We can use identity columns as key to generate ids for records and this will work for most of the use cases where the uniqueness is for a particular type but when we move across types or entities this approach cannot be used as it is restricted to a table.
41 |
42 | ## Understanding the requirements again with examples
43 |
44 | Consider capturing of occurrences in distributed systems may be take an example of online shopping systems. Item added to cart where the cart with an id. Check out will have an id, payment will have an id and shipment will have an id and delivery notification with an id. It would be easy for someone who monitors the system to track these since the events will have identifiers which having identifiers in increasing order and gives a clear indication that payment event occurred after order event.
45 |
46 | One more example that we can think of is - Social networking site where user creates a post with a unique id. These posts attract likes, comments from users or people who subscribed to certain types of events. In this it would be useful to understand and trace a like or comment to a post will always have an identifier which is greater than the post itself.
47 |
48 | ## Centralized Id generation
49 |
50 | We can have a service that can generate identifiers and distribute them to services. We need to handle concurrency and synchoronization. Consider the scale at which requests come for Twitter, Flickr, sale day in Amazon or Flipkart. We expect on an average of 10000 requests per second and having a centralized service to handle requests at this scale is not easy and any failure will have impact on the platform.
51 |
52 | ## Id generation based on Twitter snowflake algorithm will help here.
53 |
54 | https://blog.twitter.com/engineering/en_us/a/2010/announcing-snowflake.html
55 |
56 | Other references
57 | https://github.com/sony/sonyflake
58 | https://instagram-engineering.com/sharding-ids-at-instagram-1cf5a71e5a5c
59 | https://docs.mongodb.com/manual/reference/method/ObjectId/
60 |
61 |
--------------------------------------------------------------------------------
/build.gradle:
--------------------------------------------------------------------------------
1 | plugins {
2 | id 'org.springframework.boot' version '2.2.6.RELEASE'
3 | id 'io.spring.dependency-management' version '1.0.9.RELEASE'
4 | id 'java'
5 | }
6 |
7 | group 'com.gb.didgen'
8 | version '1.0-SNAPSHOT'
9 |
10 | sourceCompatibility = 1.8
11 |
12 | repositories {
13 | mavenCentral()
14 | jcenter()
15 | }
16 |
17 | dependencies {
18 | compile 'org.springframework.boot:spring-boot-starter-web'
19 | compile group: 'org.apache.commons', name: 'commons-lang3', version: '3.10'
20 | compile('com.fasterxml.jackson.datatype:jackson-datatype-jsr310')
21 | compileOnly 'org.projectlombok:lombok:1.18.12'
22 | compile group: 'org.apache.commons', name: 'commons-lang3', version: '3.10'
23 | annotationProcessor 'org.projectlombok:lombok:1.18.12'
24 | testImplementation 'org.junit.jupiter:junit-jupiter-api:5.3.1'
25 | testRuntimeOnly 'org.junit.jupiter:junit-jupiter-engine:5.3.1'
26 | // https://mvnrepository.com/artifact/org.mockito/mockito-junit-jupiter
27 | testCompile group: 'org.mockito', name: 'mockito-junit-jupiter', version: '3.3.3'
28 | }
29 | test {
30 | useJUnitPlatform()
31 | }
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/gradle/wrapper/gradle-wrapper.jar:
--------------------------------------------------------------------------------
https://raw.githubusercontent.com/gopalbala/distributed-idgen/9100eb3b9dfeaf36fdc64d34cff207cdad22464a/gradle/wrapper/gradle-wrapper.jar
--------------------------------------------------------------------------------
/gradle/wrapper/gradle-wrapper.properties:
--------------------------------------------------------------------------------
1 | #Sat Jul 04 20:51:43 IST 2020
2 | distributionUrl=https\://services.gradle.org/distributions/gradle-5.2.1-all.zip
3 | distributionBase=GRADLE_USER_HOME
4 | distributionPath=wrapper/dists
5 | zipStorePath=wrapper/dists
6 | zipStoreBase=GRADLE_USER_HOME
7 |
--------------------------------------------------------------------------------
/gradlew:
--------------------------------------------------------------------------------
1 | #!/usr/bin/env sh
2 |
3 | ##############################################################################
4 | ##
5 | ## Gradle start up script for UN*X
6 | ##
7 | ##############################################################################
8 |
9 | # Attempt to set APP_HOME
10 | # Resolve links: $0 may be a link
11 | PRG="$0"
12 | # Need this for relative symlinks.
13 | while [ -h "$PRG" ] ; do
14 | ls=`ls -ld "$PRG"`
15 | link=`expr "$ls" : '.*-> \(.*\)$'`
16 | if expr "$link" : '/.*' > /dev/null; then
17 | PRG="$link"
18 | else
19 | PRG=`dirname "$PRG"`"/$link"
20 | fi
21 | done
22 | SAVED="`pwd`"
23 | cd "`dirname \"$PRG\"`/" >/dev/null
24 | APP_HOME="`pwd -P`"
25 | cd "$SAVED" >/dev/null
26 |
27 | APP_NAME="Gradle"
28 | APP_BASE_NAME=`basename "$0"`
29 |
30 | # Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
31 | DEFAULT_JVM_OPTS='"-Xmx64m"'
32 |
33 | # Use the maximum available, or set MAX_FD != -1 to use that value.
34 | MAX_FD="maximum"
35 |
36 | warn () {
37 | echo "$*"
38 | }
39 |
40 | die () {
41 | echo
42 | echo "$*"
43 | echo
44 | exit 1
45 | }
46 |
47 | # OS specific support (must be 'true' or 'false').
48 | cygwin=false
49 | msys=false
50 | darwin=false
51 | nonstop=false
52 | case "`uname`" in
53 | CYGWIN* )
54 | cygwin=true
55 | ;;
56 | Darwin* )
57 | darwin=true
58 | ;;
59 | MINGW* )
60 | msys=true
61 | ;;
62 | NONSTOP* )
63 | nonstop=true
64 | ;;
65 | esac
66 |
67 | CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
68 |
69 | # Determine the Java command to use to start the JVM.
70 | if [ -n "$JAVA_HOME" ] ; then
71 | if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
72 | # IBM's JDK on AIX uses strange locations for the executables
73 | JAVACMD="$JAVA_HOME/jre/sh/java"
74 | else
75 | JAVACMD="$JAVA_HOME/bin/java"
76 | fi
77 | if [ ! -x "$JAVACMD" ] ; then
78 | die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME
79 |
80 | Please set the JAVA_HOME variable in your environment to match the
81 | location of your Java installation."
82 | fi
83 | else
84 | JAVACMD="java"
85 | which java >/dev/null 2>&1 || die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
86 |
87 | Please set the JAVA_HOME variable in your environment to match the
88 | location of your Java installation."
89 | fi
90 |
91 | # Increase the maximum file descriptors if we can.
92 | if [ "$cygwin" = "false" -a "$darwin" = "false" -a "$nonstop" = "false" ] ; then
93 | MAX_FD_LIMIT=`ulimit -H -n`
94 | if [ $? -eq 0 ] ; then
95 | if [ "$MAX_FD" = "maximum" -o "$MAX_FD" = "max" ] ; then
96 | MAX_FD="$MAX_FD_LIMIT"
97 | fi
98 | ulimit -n $MAX_FD
99 | if [ $? -ne 0 ] ; then
100 | warn "Could not set maximum file descriptor limit: $MAX_FD"
101 | fi
102 | else
103 | warn "Could not query maximum file descriptor limit: $MAX_FD_LIMIT"
104 | fi
105 | fi
106 |
107 | # For Darwin, add options to specify how the application appears in the dock
108 | if $darwin; then
109 | GRADLE_OPTS="$GRADLE_OPTS \"-Xdock:name=$APP_NAME\" \"-Xdock:icon=$APP_HOME/media/gradle.icns\""
110 | fi
111 |
112 | # For Cygwin, switch paths to Windows format before running java
113 | if $cygwin ; then
114 | APP_HOME=`cygpath --path --mixed "$APP_HOME"`
115 | CLASSPATH=`cygpath --path --mixed "$CLASSPATH"`
116 | JAVACMD=`cygpath --unix "$JAVACMD"`
117 |
118 | # We build the pattern for arguments to be converted via cygpath
119 | ROOTDIRSRAW=`find -L / -maxdepth 1 -mindepth 1 -type d 2>/dev/null`
120 | SEP=""
121 | for dir in $ROOTDIRSRAW ; do
122 | ROOTDIRS="$ROOTDIRS$SEP$dir"
123 | SEP="|"
124 | done
125 | OURCYGPATTERN="(^($ROOTDIRS))"
126 | # Add a user-defined pattern to the cygpath arguments
127 | if [ "$GRADLE_CYGPATTERN" != "" ] ; then
128 | OURCYGPATTERN="$OURCYGPATTERN|($GRADLE_CYGPATTERN)"
129 | fi
130 | # Now convert the arguments - kludge to limit ourselves to /bin/sh
131 | i=0
132 | for arg in "$@" ; do
133 | CHECK=`echo "$arg"|egrep -c "$OURCYGPATTERN" -`
134 | CHECK2=`echo "$arg"|egrep -c "^-"` ### Determine if an option
135 |
136 | if [ $CHECK -ne 0 ] && [ $CHECK2 -eq 0 ] ; then ### Added a condition
137 | eval `echo args$i`=`cygpath --path --ignore --mixed "$arg"`
138 | else
139 | eval `echo args$i`="\"$arg\""
140 | fi
141 | i=$((i+1))
142 | done
143 | case $i in
144 | (0) set -- ;;
145 | (1) set -- "$args0" ;;
146 | (2) set -- "$args0" "$args1" ;;
147 | (3) set -- "$args0" "$args1" "$args2" ;;
148 | (4) set -- "$args0" "$args1" "$args2" "$args3" ;;
149 | (5) set -- "$args0" "$args1" "$args2" "$args3" "$args4" ;;
150 | (6) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" ;;
151 | (7) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" ;;
152 | (8) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" ;;
153 | (9) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" "$args8" ;;
154 | esac
155 | fi
156 |
157 | # Escape application args
158 | save () {
159 | for i do printf %s\\n "$i" | sed "s/'/'\\\\''/g;1s/^/'/;\$s/\$/' \\\\/" ; done
160 | echo " "
161 | }
162 | APP_ARGS=$(save "$@")
163 |
164 | # Collect all arguments for the java command, following the shell quoting and substitution rules
165 | eval set -- $DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS "\"-Dorg.gradle.appname=$APP_BASE_NAME\"" -classpath "\"$CLASSPATH\"" org.gradle.wrapper.GradleWrapperMain "$APP_ARGS"
166 |
167 | # by default we should be in the correct project dir, but when run from Finder on Mac, the cwd is wrong
168 | if [ "$(uname)" = "Darwin" ] && [ "$HOME" = "$PWD" ]; then
169 | cd "$(dirname "$0")"
170 | fi
171 |
172 | exec "$JAVACMD" "$@"
173 |
--------------------------------------------------------------------------------
/gradlew.bat:
--------------------------------------------------------------------------------
1 | @if "%DEBUG%" == "" @echo off
2 | @rem ##########################################################################
3 | @rem
4 | @rem Gradle startup script for Windows
5 | @rem
6 | @rem ##########################################################################
7 |
8 | @rem Set local scope for the variables with windows NT shell
9 | if "%OS%"=="Windows_NT" setlocal
10 |
11 | set DIRNAME=%~dp0
12 | if "%DIRNAME%" == "" set DIRNAME=.
13 | set APP_BASE_NAME=%~n0
14 | set APP_HOME=%DIRNAME%
15 |
16 | @rem Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
17 | set DEFAULT_JVM_OPTS="-Xmx64m"
18 |
19 | @rem Find java.exe
20 | if defined JAVA_HOME goto findJavaFromJavaHome
21 |
22 | set JAVA_EXE=java.exe
23 | %JAVA_EXE% -version >NUL 2>&1
24 | if "%ERRORLEVEL%" == "0" goto init
25 |
26 | echo.
27 | echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
28 | echo.
29 | echo Please set the JAVA_HOME variable in your environment to match the
30 | echo location of your Java installation.
31 |
32 | goto fail
33 |
34 | :findJavaFromJavaHome
35 | set JAVA_HOME=%JAVA_HOME:"=%
36 | set JAVA_EXE=%JAVA_HOME%/bin/java.exe
37 |
38 | if exist "%JAVA_EXE%" goto init
39 |
40 | echo.
41 | echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME%
42 | echo.
43 | echo Please set the JAVA_HOME variable in your environment to match the
44 | echo location of your Java installation.
45 |
46 | goto fail
47 |
48 | :init
49 | @rem Get command-line arguments, handling Windows variants
50 |
51 | if not "%OS%" == "Windows_NT" goto win9xME_args
52 |
53 | :win9xME_args
54 | @rem Slurp the command line arguments.
55 | set CMD_LINE_ARGS=
56 | set _SKIP=2
57 |
58 | :win9xME_args_slurp
59 | if "x%~1" == "x" goto execute
60 |
61 | set CMD_LINE_ARGS=%*
62 |
63 | :execute
64 | @rem Setup the command line
65 |
66 | set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar
67 |
68 | @rem Execute Gradle
69 | "%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" org.gradle.wrapper.GradleWrapperMain %CMD_LINE_ARGS%
70 |
71 | :end
72 | @rem End local scope for the variables with windows NT shell
73 | if "%ERRORLEVEL%"=="0" goto mainEnd
74 |
75 | :fail
76 | rem Set variable GRADLE_EXIT_CONSOLE if you need the _script_ return code instead of
77 | rem the _cmd.exe /c_ return code!
78 | if not "" == "%GRADLE_EXIT_CONSOLE%" exit 1
79 | exit /b 1
80 |
81 | :mainEnd
82 | if "%OS%"=="Windows_NT" endlocal
83 |
84 | :omega
85 |
--------------------------------------------------------------------------------
/settings.gradle:
--------------------------------------------------------------------------------
1 | rootProject.name = 'distributed-idgen'
2 |
3 |
--------------------------------------------------------------------------------
/src/main/java/com/gb/didgen/BeanDefinition.java:
--------------------------------------------------------------------------------
1 | package com.gb.didgen;
2 |
3 | import org.springframework.context.annotation.Bean;
4 | import org.springframework.stereotype.Component;
5 |
6 | import java.net.NetworkInterface;
7 | import java.net.SocketException;
8 | import java.security.SecureRandom;
9 | import java.util.Enumeration;
10 |
11 | import static com.gb.didgen.common.Constants.NODE_ID_BIT_LEN;
12 |
13 | @Component
14 | public class BeanDefinition {
15 | @Bean
16 | public Integer generatingNodeId() {
17 | int maxNodeVal = (int) Math.pow(2, NODE_ID_BIT_LEN);
18 | int nodeId;
19 | try {
20 | StringBuilder sb = new StringBuilder();
21 | Enumeration networkInterfaces = NetworkInterface.getNetworkInterfaces();
22 | while (networkInterfaces.hasMoreElements()) {
23 | NetworkInterface networkInterface = networkInterfaces.nextElement();
24 | byte[] mac = networkInterface.getHardwareAddress();
25 | if (mac != null) {
26 | for (int i = 0; i < mac.length; i++) {
27 | sb.append(String.format("%02X", mac[i]));
28 | }
29 | }
30 | }
31 | nodeId = sb.toString().hashCode();
32 | } catch (SocketException ex) {
33 | //in case of exception get a random number limited by max node size
34 | nodeId = (int) (new SecureRandom().nextInt() % Math.pow(2, 10));
35 | }
36 | nodeId = nodeId & maxNodeVal;
37 | return nodeId;
38 | }
39 | }
40 |
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/src/main/java/com/gb/didgen/DistributedIdDesignMain.java:
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1 | package com.gb.didgen;
2 |
3 | import org.springframework.boot.SpringApplication;
4 | import org.springframework.boot.autoconfigure.SpringBootApplication;
5 |
6 | @SpringBootApplication
7 | public class DistributedIdDesignMain {
8 | public static void main(String[] args) {
9 | SpringApplication.run(DistributedIdDesignMain.class);
10 | }
11 | }
12 |
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/src/main/java/com/gb/didgen/IdGeneratorController.java:
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1 | package com.gb.didgen;
2 |
3 | import com.gb.didgen.exception.ClockMovedBackException;
4 | import com.gb.didgen.exception.NodeIdOutOfBoundException;
5 | import com.gb.didgen.service.SequenceIdGenerator;
6 | import org.springframework.beans.factory.annotation.Autowired;
7 | import org.springframework.http.ResponseEntity;
8 | import org.springframework.web.bind.annotation.GetMapping;
9 | import org.springframework.web.bind.annotation.RestController;
10 |
11 | @RestController()
12 | public class IdGeneratorController {
13 | @Autowired
14 | private SequenceIdGenerator sequenceIdGenerator;
15 |
16 | @GetMapping(produces = {"application/JSON"})
17 | public ResponseEntity> getNextId() throws NodeIdOutOfBoundException, ClockMovedBackException {
18 | return ResponseEntity.ok(sequenceIdGenerator.generateId());
19 | }
20 | }
21 |
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/src/main/java/com/gb/didgen/common/Constants.java:
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1 | package com.gb.didgen.common;
2 |
3 | public class Constants {
4 | public static final int SIGN_BIT_LEN = 1;
5 | public static final int EPOCH_BIT_LEN = 41;
6 | public static final int NODE_ID_BIT_LEN = 10;
7 | public static final int SEQUENCE_BIT_LEN = 12;
8 | }
9 |
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/src/main/java/com/gb/didgen/exception/ClockMovedBackException.java:
--------------------------------------------------------------------------------
1 | package com.gb.didgen.exception;
2 |
3 | public class ClockMovedBackException extends Exception {
4 | public ClockMovedBackException(String message) {
5 | super(message);
6 | }
7 | }
8 |
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/src/main/java/com/gb/didgen/exception/NodeIdOutOfBoundException.java:
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1 | package com.gb.didgen.exception;
2 |
3 | public class NodeIdOutOfBoundException extends Exception {
4 | public NodeIdOutOfBoundException(String message) {
5 | super(message);
6 | }
7 | }
8 |
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/src/main/java/com/gb/didgen/service/IdGenerator.java:
--------------------------------------------------------------------------------
1 | package com.gb.didgen.service;
2 |
3 | public interface IdGenerator {
4 | String generateId();
5 | }
6 |
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/src/main/java/com/gb/didgen/service/SequenceIdGenerator.java:
--------------------------------------------------------------------------------
1 | package com.gb.didgen.service;
2 |
3 | import com.gb.didgen.exception.ClockMovedBackException;
4 | import com.gb.didgen.exception.NodeIdOutOfBoundException;
5 | import org.springframework.stereotype.Service;
6 |
7 | @Service
8 | public interface SequenceIdGenerator {
9 | long generateId() throws ClockMovedBackException, NodeIdOutOfBoundException;
10 | }
11 |
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/src/main/java/com/gb/didgen/service/SnowflakeSequenceIdGenerator.java:
--------------------------------------------------------------------------------
1 | package com.gb.didgen.service;
2 |
3 | import com.gb.didgen.exception.ClockMovedBackException;
4 | import com.gb.didgen.exception.NodeIdOutOfBoundException;
5 | import org.springframework.beans.factory.annotation.Autowired;
6 | import org.springframework.stereotype.Service;
7 |
8 | import javax.annotation.PostConstruct;
9 | import java.time.Instant;
10 |
11 | import static com.gb.didgen.common.Constants.NODE_ID_BIT_LEN;
12 | import static com.gb.didgen.common.Constants.SEQUENCE_BIT_LEN;
13 |
14 | @Service
15 | public class SnowflakeSequenceIdGenerator implements SequenceIdGenerator {
16 | @Autowired
17 | private Integer generatingNodeId;
18 |
19 | private final int maxSequence = (int) Math.pow(2, SEQUENCE_BIT_LEN);
20 | private final int maxNodeVal = (int) Math.pow(2, NODE_ID_BIT_LEN);
21 | private final long EPOCH_START = Instant.EPOCH.toEpochMilli();
22 |
23 |
24 | private volatile long currentSequence = -1L;
25 | private final Object lock = new Object();
26 | private volatile long lastTimestamp = -1L;
27 |
28 | @PostConstruct
29 | public void checkNodeIdBounds() throws NodeIdOutOfBoundException {
30 | if (generatingNodeId < 0 || generatingNodeId > maxNodeVal) {
31 | throw new NodeIdOutOfBoundException("Node id is < 0 or > " + maxNodeVal);
32 | }
33 | }
34 |
35 | @Override
36 | public long generateId() throws ClockMovedBackException, NodeIdOutOfBoundException {
37 | checkNodeIdBounds();
38 | synchronized (lock) {
39 | long currentTimeStamp = getTimeStamp();
40 | if (currentTimeStamp < lastTimestamp) {
41 | throw new ClockMovedBackException("Clock moved back");
42 | }
43 | if (currentTimeStamp == lastTimestamp) {
44 | currentSequence = currentSequence + 1 & maxSequence;
45 | if (currentSequence != 0) {
46 | currentTimeStamp = waitNextMillis(currentTimeStamp);
47 | }
48 | } else {
49 | currentSequence = 0;
50 | }
51 | lastTimestamp = currentTimeStamp;
52 | long id = currentTimeStamp << (NODE_ID_BIT_LEN + SEQUENCE_BIT_LEN);
53 | id |= (generatingNodeId << SEQUENCE_BIT_LEN);
54 | id |= currentSequence;
55 | return id;
56 | }
57 | }
58 |
59 | private long getTimeStamp() {
60 | return Instant.now().toEpochMilli() - EPOCH_START;
61 | }
62 |
63 | private long waitNextMillis(long currentTimeStamp) {
64 | while (currentTimeStamp == lastTimestamp) {
65 | currentTimeStamp = getTimeStamp();
66 | }
67 | return currentTimeStamp;
68 | }
69 | }
70 |
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/src/main/java/com/gb/didgen/service/UUIDGenerator.java:
--------------------------------------------------------------------------------
1 | package com.gb.didgen.service;
2 |
3 | import java.util.UUID;
4 |
5 | public class UUIDGenerator implements IdGenerator {
6 | @Override
7 | public String generateId() {
8 | return UUID.randomUUID().toString();
9 | }
10 | }
11 |
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/src/main/resources/application.yml:
--------------------------------------------------------------------------------
1 | server:
2 | port: 8090
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