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Microsoft JDBC Driver for SQL Server.
There is a newer version: 12.8.1.jre11
/*
 * Microsoft JDBC Driver for SQL Server
 * 
 * Copyright(c) Microsoft Corporation All rights reserved.
 * 
 * This program is made available under the terms of the MIT License. See the LICENSE file in the project root for more information.
 */

package com.microsoft.sqlserver.jdbc;

import java.util.Map;
import java.util.UUID;
import java.util.concurrent.ConcurrentHashMap;

/**
 * ActivityCorrelator provides the APIs to access the ActivityId in TLS
 */
final class ActivityCorrelator {

    private static Map ActivityIdTlsMap = new ConcurrentHashMap();
    
    static void cleanupActivityId() {
        //remove the ActivityId that belongs to this thread.
        long uniqueThreadId = Thread.currentThread().getId();

        if (ActivityIdTlsMap.containsKey(uniqueThreadId)) {
            ActivityIdTlsMap.remove(uniqueThreadId);
        }
    }

    // Get the current ActivityId in TLS
    static ActivityId getCurrent() {
        // get the value in TLS, not reference
        long uniqueThreadId = Thread.currentThread().getId();
        
        //Since the Id for each thread is unique, this assures that the below if statement is run only once per thread.
        if (!ActivityIdTlsMap.containsKey(uniqueThreadId)) {
            ActivityIdTlsMap.put(uniqueThreadId, new ActivityId());
        }
        
        return ActivityIdTlsMap.get(uniqueThreadId);
    }

    // Increment the Sequence number of the ActivityId in TLS
    // and return the ActivityId with new Sequence number
    static ActivityId getNext() {
        // Get the current ActivityId in TLS
        ActivityId activityId = getCurrent();

        // Increment the Sequence number
        activityId.Increment();

        return activityId;
    }

    static void setCurrentActivityIdSentFlag() {
        ActivityId activityId = getCurrent();
        activityId.setSentFlag();
    }
}

class ActivityId {
    private final UUID Id;
    private long Sequence;
    private boolean isSentToServer;

    ActivityId() {
        Id = UUID.randomUUID();
        Sequence = 0;
        isSentToServer = false;
    }

    UUID getId() {
        return Id;
    }

    long getSequence() {
        return Sequence;
    }

    void Increment() {
        if (Sequence < 0xffffffffl) // to get to 32-bit unsigned
        {
            ++Sequence;
        }
        else {
            Sequence = 0;
        }

        isSentToServer = false;
    }

    void setSentFlag() {
        isSentToServer = true;
    }

    boolean IsSentToServer() {
        return isSentToServer;
    }

    @Override
    public String toString() {
        StringBuilder sb = new StringBuilder();
        sb.append(Id.toString());
        sb.append("-");
        sb.append(Sequence);
        return sb.toString();
    }
}