#87 feat: snow flake 객체 id 생성기

src/main/java/com/seoultech/synergybe/domain/common/idgenerator/IdGeneratorSnowFlake.java

@@ -0,0 +1,141 @@
+package com.seoultech.synergybe.domain.common.idgenerator;
+
+import org.springframework.stereotype.Component;
+
+import java.net.NetworkInterface;
+import java.security.SecureRandom;
+import java.time.Instant;
+import java.util.Enumeration;
+
+/**
+ * Distributed Sequence Generator.
+ * Inspired by Twitter snowflake: https://github.com/twitter/snowflake/tree/snowflake-2010
+ *
+ * This class should be used as a Singleton.
+ * Make sure that you create and reuse a Single instance of Snowflake per node in your distributed system cluster.
+ */
+@Component
+public class IdGeneratorSnowFlake implements IdGenerator {
+    private static final int UNUSED_BITS = 1; // Sign bit, Unused (always set to 0)
+    private static final int EPOCH_BITS = 41;
+    private static final int NODE_ID_BITS = 10;
+    private static final int SEQUENCE_BITS = 12;
+
+    private static final long maxNodeId = (1L << NODE_ID_BITS) - 1;
+    private static final long maxSequence = (1L << SEQUENCE_BITS) - 1;
+
+    // Custom Epoch (January 1, 2015 Midnight UTC = 2015-01-01T00:00:00Z)
+    private static final long DEFAULT_CUSTOM_EPOCH = 1420070400000L;
+
+    private final long nodeId;
+    private final long customEpoch;
+
+    private volatile long lastTimestamp = -1L;
+    private volatile long sequence = 0L;
+
+    // Create Snowflake with a nodeId and custom epoch
+    public IdGeneratorSnowFlake(long nodeId, long customEpoch) {
+        if(nodeId < 0 || nodeId > maxNodeId) {
+            throw new IllegalArgumentException(String.format("NodeId must be between %d and %d", 0, maxNodeId));
+        }
+        this.nodeId = nodeId;
+        this.customEpoch = customEpoch;
+    }
+
+    // Create Snowflake with a nodeId
+    public IdGeneratorSnowFlake(long nodeId) {
+        this(nodeId, DEFAULT_CUSTOM_EPOCH);
+    }
+
+    // Let Snowflake generate a nodeId
+    public IdGeneratorSnowFlake() {
+        this.nodeId = createNodeId();
+        this.customEpoch = DEFAULT_CUSTOM_EPOCH;
+    }
+
+    public String generateId(IdPrefix idPrefix) {
+        long id = nextId();
+        return String.valueOf(id);
+    }
+
+    public synchronized long nextId() {
+        long currentTimestamp = timestamp();
+
+        if(currentTimestamp < lastTimestamp) {
+            throw new IllegalStateException("Invalid System Clock!");
+        }
+
+        if (currentTimestamp == lastTimestamp) {
+            sequence = (sequence + 1) & maxSequence;
+            if(sequence == 0) {
+                // Sequence Exhausted, wait till next millisecond.
+                currentTimestamp = waitNextMillis(currentTimestamp);
+            }
+        } else {
+            // reset sequence to start with zero for the next millisecond
+            sequence = 0;
+        }
+
+        lastTimestamp = currentTimestamp;
+
+        long id = currentTimestamp << (NODE_ID_BITS + SEQUENCE_BITS)
+                | (nodeId << SEQUENCE_BITS)
+                | sequence;
+
+        return id;
+    }
+
+
+    // Get current timestamp in milliseconds, adjust for the custom epoch.
+    private long timestamp() {
+        return Instant.now().toEpochMilli() - customEpoch;
+    }
+
+    // Block and wait till next millisecond
+    private long waitNextMillis(long currentTimestamp) {
+        while (currentTimestamp == lastTimestamp) {
+            currentTimestamp = timestamp();
+        }
+        return currentTimestamp;
+    }
+
+    private long createNodeId() {
+        long nodeId;
+        try {
+            StringBuilder sb = new StringBuilder();
+            Enumeration<NetworkInterface> networkInterfaces = NetworkInterface.getNetworkInterfaces();
+            while (networkInterfaces.hasMoreElements()) {
+                NetworkInterface networkInterface = networkInterfaces.nextElement();
+                byte[] mac = networkInterface.getHardwareAddress();
+                if (mac != null) {
+                    for(byte macPort: mac) {
+                        sb.append(String.format("%02X", macPort));
+                    }
+                }
+            }
+            nodeId = sb.toString().hashCode();
+        } catch (Exception ex) {
+            nodeId = (new SecureRandom().nextInt());
+        }
+        nodeId = nodeId & maxNodeId;
+        return nodeId;
+    }
+
+    public long[] parse(long id) {
+        long maskNodeId = ((1L << NODE_ID_BITS) - 1) << SEQUENCE_BITS;
+        long maskSequence = (1L << SEQUENCE_BITS) - 1;
+
+        long timestamp = (id >> (NODE_ID_BITS + SEQUENCE_BITS)) + customEpoch;
+        long nodeId = (id & maskNodeId) >> SEQUENCE_BITS;
+        long sequence = id & maskSequence;
+
+        return new long[]{timestamp, nodeId, sequence};
+    }
+
+    @Override
+    public String toString() {
+        return "Snowflake Settings [EPOCH_BITS=" + EPOCH_BITS + ", NODE_ID_BITS=" + NODE_ID_BITS
+                + ", SEQUENCE_BITS=" + SEQUENCE_BITS + ", CUSTOM_EPOCH=" + customEpoch
+                + ", NodeId=" + nodeId + "]";
+    }
+}