diff --git a/include/NacosExceptions.h b/include/NacosExceptions.h
index 56f9561..be451fd 100644
--- a/include/NacosExceptions.h
+++ b/include/NacosExceptions.h
@@ -81,6 +81,7 @@ class NacosException : public std::exception {
     static const int UNABLE_TO_GET_HOST_IP = 1008;
     static const int UNABLE_TO_CREATE_SOCKET = 1009;
     static const int INVALID_CONFIG_PARAM = 1010;
+    static const int UNABLE_TO_GET_HOST_NAME = 1011;
 
 };
 
diff --git a/include/constant/PropertyKeyConst.h b/include/constant/PropertyKeyConst.h
index 83e98be..647ff9f 100644
--- a/include/constant/PropertyKeyConst.h
+++ b/include/constant/PropertyKeyConst.h
@@ -58,6 +58,10 @@ class PropertyKeyConst {
 
     static const int NACOS_DEFAULT_PORT = 8848;
 
+    static const NacosString INSTANCE_ID_SEQ_FILE;
+
+    static const NacosString INSTANCE_ID_PREFIX;
+
     /*public static class SystemEnv {
 
         static const NacosString ALIBABA_ALIWARE_ENDPOINT_PORT = "ALIBABA_ALIWARE_ENDPOINT_PORT";
diff --git a/include/listen/Listener.h b/include/listen/Listener.h
index eb00f7e..acd596e 100644
--- a/include/listen/Listener.h
+++ b/include/listen/Listener.h
@@ -8,7 +8,7 @@ namespace nacos{
 class Listener {
 private:
     NacosString listenerName;
-    AtomicInt refCount;
+    AtomicInt<int> refCount;
 public:
     Listener() {
         this->listenerName = "theListener";
diff --git a/include/naming/subscribe/EventListener.h b/include/naming/subscribe/EventListener.h
index f7a6c05..1341b62 100644
--- a/include/naming/subscribe/EventListener.h
+++ b/include/naming/subscribe/EventListener.h
@@ -14,7 +14,7 @@ namespace nacos{
 class EventListener {
 private:
     NacosString listenerName;
-    AtomicInt refCount;
+    AtomicInt<int> refCount;
 public:
     EventListener() {
         this->listenerName = "theListener";
diff --git a/include/thread/AtomicInt.h b/include/thread/AtomicInt.h
index dc50576..0786f94 100644
--- a/include/thread/AtomicInt.h
+++ b/include/thread/AtomicInt.h
@@ -2,22 +2,30 @@
 #define __ATOMIC_INT_H_
 
 namespace nacos{
+template<typename T>
 class AtomicInt {
 private:
-    volatile int _intval;
+    volatile T _curval;
 public:
-    AtomicInt(int initval = 0) : _intval(initval) {};
+    AtomicInt(T curval = 0) : _curval(curval) {};
 
-    int inc(int incval = 1) {
-        int oldValue = __sync_fetch_and_add(&_intval, incval);
+    void set(T val) { _curval = val; };
+
+    T inc(T incval = 1) {
+        T oldValue = getAndInc(incval);
         return incval + oldValue;
     };
 
-    int dec(int decval = 1) {
+    T getAndInc(T incval = 1) {
+        T oldValue = __sync_fetch_and_add(&_curval, incval);
+        return oldValue;
+    }
+
+    T dec(int decval = 1) {
         return inc(-decval);
     };
 
-    int get() const { return _intval; };
+    T get() const { return _curval; };
 };
 }//namespace nacos
 
diff --git a/src/config/AppConfigManager.cpp b/src/config/AppConfigManager.cpp
index ff76a64..935c5c0 100644
--- a/src/config/AppConfigManager.cpp
+++ b/src/config/AppConfigManager.cpp
@@ -102,6 +102,8 @@ void AppConfigManager::initDefaults() {
 
     NacosString homedir = DirUtils::getHome();
 
+    set(PropertyKeyConst::INSTANCE_ID_PREFIX, NetUtils::getHostName());
+    set(PropertyKeyConst::INSTANCE_ID_SEQ_FILE, homedir + ConfigConstant::FILE_SEPARATOR + "nacos" + ConfigConstant::FILE_SEPARATOR + "instance_seq.dat");
     set(PropertyKeyConst::NACOS_SNAPSHOT_PATH, homedir + ConfigConstant::FILE_SEPARATOR + "nacos" + ConfigConstant::FILE_SEPARATOR + "snapshot");
     log_info("[AppConfigManager]-initDefaults:DEFAULT_SNAPSHOT_PATH:%s\n", appConfig[PropertyKeyConst::NACOS_SNAPSHOT_PATH].c_str());
 }
diff --git a/src/constant/PropertyKeyConst.cpp b/src/constant/PropertyKeyConst.cpp
index 0db1d0b..36aa952 100644
--- a/src/constant/PropertyKeyConst.cpp
+++ b/src/constant/PropertyKeyConst.cpp
@@ -50,4 +50,6 @@ const NacosString PropertyKeyConst::CLIENT_NAME = "nacos.client.name";
 const NacosString PropertyKeyConst::AUTH_USERNAME = "nacos.auth.username";
 const NacosString PropertyKeyConst::AUTH_PASSWORD = "nacos.auth.password";
 const NacosString PropertyKeyConst::LOCAL_IP = "nacos.client.ip";
+const NacosString PropertyKeyConst::INSTANCE_ID_SEQ_FILE = "nacos.instId.seq.file";
+const NacosString PropertyKeyConst::INSTANCE_ID_PREFIX = "nacos.instId.prefix";
 }//namespace nacos
diff --git a/src/factory/NacosServiceFactory.cpp b/src/factory/NacosServiceFactory.cpp
index 86914a1..d8ce633 100644
--- a/src/factory/NacosServiceFactory.cpp
+++ b/src/factory/NacosServiceFactory.cpp
@@ -19,6 +19,7 @@
 #include "src/naming/subscribe/HostReactor.h"
 #include "src/security/SecurityManager.h"
 #include "src/utils/ConfigParserUtils.h"
+#include "src/utils/SequenceProvider.h"
 #include "utils/DirUtils.h"
 
 //Unlike Java, in cpp, there's no container, no spring to do the ORM job, so I have to handle it myself
@@ -114,6 +115,10 @@ NamingService *NacosServiceFactory::CreateNamingService() NACOS_THROW(NacosExcep
     HostReactor *hostReactor = new HostReactor(objectConfigData);
     objectConfigData->_hostReactor = hostReactor;
 
+    const NacosString &seqConfile = appConfigManager->get(PropertyKeyConst::INSTANCE_ID_SEQ_FILE);
+    SequenceProvider<int64_t> *sequenceProvider = new SequenceProvider<int64_t>(seqConfile, 1, 10);
+    objectConfigData->_sequenceProvider = sequenceProvider;
+
     objectConfigData->checkAssembledObject();
     NamingService *instance = new NacosNamingService(objectConfigData);
 
diff --git a/src/factory/ObjectConfigData.cpp b/src/factory/ObjectConfigData.cpp
index 68be291..42be791 100644
--- a/src/factory/ObjectConfigData.cpp
+++ b/src/factory/ObjectConfigData.cpp
@@ -9,6 +9,7 @@
 #include "src/listen/ClientWorker.h"
 #include "src/security/SecurityManager.h"
 #include "utils/UuidUtils.h"
+#include "src/utils/SequenceProvider.h"
 
 namespace nacos{
 
@@ -44,6 +45,7 @@ void ObjectConfigData::checkNamingService() NACOS_THROW(NacosException) {
     NACOS_ASSERT(_serverListManager != NULL);
     NACOS_ASSERT(_udpNamingServiceListener != NULL);
     NACOS_ASSERT(_udpNamingServiceListener != NULL);
+    NACOS_ASSERT(_sequenceProvider != NULL);
 }
 
 void ObjectConfigData::checkConfigService() NACOS_THROW(NacosException) {
@@ -206,6 +208,12 @@ void ObjectConfigData::destroyNamingService() {
         delete _appConfigManager;
         _appConfigManager = NULL;
     }
+
+    if (_sequenceProvider != NULL)
+    {
+        delete _sequenceProvider;
+        _sequenceProvider = NULL;
+    }
 }
 
 void ObjectConfigData::destroyMaintainService() {
diff --git a/src/factory/ObjectConfigData.h b/src/factory/ObjectConfigData.h
index 0a3258c..c708a7d 100644
--- a/src/factory/ObjectConfigData.h
+++ b/src/factory/ObjectConfigData.h
@@ -20,6 +20,7 @@ class LocalSnapshotManager;
 class SecurityManager;
 class UdpNamingServiceListener;
 class HostReactor;
+template <typename T>class SequenceProvider;
 
 enum FactoryType {
     CONFIG = 0,
@@ -58,6 +59,7 @@ class ObjectConfigData {
     SecurityManager *_securityManager;
     UdpNamingServiceListener *_udpNamingServiceListener;
     HostReactor *_hostReactor;
+    SequenceProvider<int64_t> *_sequenceProvider;
 };
 }//namespace nacos
 
diff --git a/src/json/JSON.cpp b/src/json/JSON.cpp
index a76b43f..c305717 100644
--- a/src/json/JSON.cpp
+++ b/src/json/JSON.cpp
@@ -110,9 +110,10 @@ long JSON::getLong(const NacosString &jsonString, const NacosString &fieldname)
 Instance JSON::Json2Instance(const Value &host) NACOS_THROW(NacosException) {
     Instance theinstance;
 
-    markRequired(host, "instanceId");
-    const Value &instanceId = host["instanceId"];
-    theinstance.instanceId = instanceId.GetString();
+    if (host.HasMember("instanceId")) {
+        const Value &instanceId = host["instanceId"];
+        theinstance.instanceId = instanceId.GetString();
+    }
 
     markRequired(host, "port");
     const Value &port = host["port"];
diff --git a/src/naming/NacosNamingService.cpp b/src/naming/NacosNamingService.cpp
index b1e3f5b..5a5b1f4 100644
--- a/src/naming/NacosNamingService.cpp
+++ b/src/naming/NacosNamingService.cpp
@@ -2,6 +2,7 @@
 #include "src/naming/subscribe/SubscriptionPoller.h"
 #include "src/naming/subscribe/UdpNamingServiceListener.h"
 #include "src/naming/beat/BeatReactor.h"
+#include "src/utils/SequenceProvider.h"
 #include "utils/NamingUtils.h"
 #include "constant/UtilAndComs.h"
 #include "utils/ParamUtils.h"
@@ -88,7 +89,8 @@ void NacosNamingService::registerInstance
                 const NacosString &groupName,
                 Instance &instance
         ) NACOS_THROW(NacosException) {
-
+    const NacosString &instanceIdPrefix = _objectConfigData->_appConfigManager->get(PropertyKeyConst::INSTANCE_ID_PREFIX);
+    instance.instanceId = instanceIdPrefix + NacosStringOps::valueOf(_objectConfigData->_sequenceProvider->next());
     if (instance.ephemeral) {
         BeatInfo beatInfo;
         beatInfo.serviceName = NamingUtils::getGroupedName(serviceName, groupName);
diff --git a/src/utils/NetUtils.cpp b/src/utils/NetUtils.cpp
index 44935a7..21aee69 100644
--- a/src/utils/NetUtils.cpp
+++ b/src/utils/NetUtils.cpp
@@ -2,9 +2,13 @@
 #include <arpa/inet.h>
 #include <sys/socket.h>
 #include <netdb.h>
+#include <errno.h>
 #include <ifaddrs.h>
 #include <src/log/Logger.h>
 #include <string.h>
+#include <unistd.h>
+
+#define HOST_AND_LEN 250
 
 namespace nacos{
 
@@ -44,4 +48,17 @@ NacosString NetUtils::getHostIp() NACOS_THROW(NacosException){
     //Usually the program will not run to here
     throw NacosException(NacosException::UNABLE_TO_GET_HOST_IP, "Failed to get IF address");
 }
+
+NacosString NetUtils::getHostName() NACOS_THROW(NacosException)
+{
+    char hostname[HOST_AND_LEN];
+    
+    int res = gethostname(hostname, HOST_AND_LEN);
+    if (res == 0) {
+        return NacosString(hostname);
+    }
+
+    throw NacosException(NacosException::UNABLE_TO_GET_HOST_NAME, "Failed to get hostname, errno = " + NacosStringOps::valueOf(errno));
+}
+
 }//namespace nacos
diff --git a/src/utils/NetUtils.h b/src/utils/NetUtils.h
index 71de3b6..bb7b23e 100644
--- a/src/utils/NetUtils.h
+++ b/src/utils/NetUtils.h
@@ -10,6 +10,9 @@ class NetUtils {
 public:
     //Get IP address (best guess)
     static NacosString getHostIp() NACOS_THROW(NacosException);
+
+    //Get hostname
+    static NacosString getHostName() NACOS_THROW(NacosException);
 };
 }//namespace nacos
 
diff --git a/src/utils/SequenceProvider.h b/src/utils/SequenceProvider.h
new file mode 100644
index 0000000..49421d4
--- /dev/null
+++ b/src/utils/SequenceProvider.h
@@ -0,0 +1,82 @@
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <errno.h>
+#include "NacosString.h"
+#include "NacosExceptions.h"
+#include "thread/AtomicInt.h"
+#include "src/thread/Mutex.h"
+#include "src/config/IOUtils.h"
+
+namespace nacos
+{
+
+template<typename T>
+class SequenceProvider {
+private:
+    NacosString _fileName;
+    AtomicInt<T> _current;
+    Mutex _acquireMutex;
+    T _nr_to_preserve;
+    T _initSequence;
+    volatile T _hwm;//high water mark
+
+    void ensureWrite(int fd, T data) {
+        size_t bytes_written = 0;
+        while (bytes_written < sizeof(T)) {
+            bytes_written += write(fd, (char*)&data + bytes_written, sizeof(T) - bytes_written);
+        }
+    }
+
+    T preserve() {
+        T current;
+        int fd;
+        bool newFile = false;
+        if (IOUtils::checkNotExistOrNotFile(_fileName)) {
+            newFile = true;
+        }
+        mode_t mode = S_IRUSR | S_IWUSR | S_IRWXG | S_IWGRP;
+        fd = open(_fileName.c_str(), O_RDWR | O_CREAT, mode);
+        if (fd <= 0) {
+            throw new NacosException(NacosException::UNABLE_TO_OPEN_FILE, _fileName);
+        }
+        
+        if (newFile) {
+            ensureWrite(fd, _initSequence);
+            lseek(fd, 0, SEEK_SET);//read from the beginning
+        }
+
+        size_t bytes_read = 0;
+        while (bytes_read < sizeof(T))
+        {
+            bytes_read += read(fd, (char*)&current + bytes_read, sizeof(T) - bytes_read);
+        }
+        lseek(fd, 0, SEEK_SET);//write from the beginning
+
+        ensureWrite(fd, current + _nr_to_preserve);
+        close(fd);
+        _hwm = current + _nr_to_preserve;
+        return current;
+    };
+public:
+    SequenceProvider(const NacosString &fileName, T initSequence, T nr_to_preserve) {
+        _fileName = fileName;
+        _initSequence = initSequence;
+        _nr_to_preserve = nr_to_preserve;
+        _current.set(preserve());
+    };
+
+    T next(int step = 1) {
+        T res = _current.getAndInc(step);
+        while (res >= _hwm) {
+            _acquireMutex.lock();
+            if (res >= _hwm) {
+                preserve();
+            }
+            _acquireMutex.unlock();
+        }
+        return res;
+    };
+};
+
+} // namespace nacos
diff --git a/test/allinone.cpp b/test/allinone.cpp
index be76a67..3f111ea 100644
--- a/test/allinone.cpp
+++ b/test/allinone.cpp
@@ -130,6 +130,8 @@ bool testNamingServiceAndDeRegisterActively();
 
 bool testThreadPoolConcurrentWithAtomicCounter();
 
+bool testSequenceProvider();
+
 TestData disabledTestList[] =
 TEST_ITEM_START
 TEST_ITEM_END
@@ -137,7 +139,6 @@ TEST_ITEM_END
 TestData
 testList[] =
 TEST_ITEM_START
-
         TEST_ITEM("Normal http test", testNormalHttpRequest)
         TEST_ITEM("No server request, should fail", testNoServerRequest)
         TEST_ITEM("Publish config to server", testPublishConfig)
@@ -152,6 +153,7 @@ TEST_ITEM_START
         TEST_ITEM("Test for string characteristics", testStringEqual)
         TEST_ITEM("Read&Write file test", testReadWriteFile)
         TEST_ITEM("GetFileSize, should work well", testGetFileSize)
+        TEST_ITEM("Test get instances with predicate(testRandomByWeightSelector)", testRandomByWeightSelector)
         TEST_ITEM("Check whether file exists or not", testFileExists)
         TEST_ITEM("Create&Remove file", testCreateAndRemove)
         TEST_ITEM("Create a directory with subdirectories, and clean it", testCleanDirectory)
@@ -170,6 +172,7 @@ TEST_ITEM_START
         TEST_ITEM("Smoke test for ThreadPool", testThreadPoolSmoke)
         TEST_ITEM("Test basic function of NacosNamingService's registerService", testNamingServiceRegister)
         TEST_ITEM("Test serialization/deserialization of Business Object", testString2ServiceInfo)
+        TEST_ITEM("Test get instances with predicate(Randomly)", testInstanceSelectors)
         TEST_ITEM("Test serialization/deserialization of malformed Business Object", testMalformedJson2ServiceInfo)
         TEST_ITEM("Test serialization/deserialization of malformed Business Object (Double)", testMalformedDouble2ServiceInfo)
         TEST_ITEM("Test serialization/deserialization of malformed Business Object (no cacheMillis)", testLackcacheMillisServiceInfo)
@@ -184,8 +187,6 @@ TEST_ITEM_START
         TEST_ITEM("Register many services and get one", testGetAllInstances)
         TEST_ITEM("Subscribe & unsubscribe services", testListenService)
         TEST_ITEM("Test get all service names", testGetServiceNames)
-        TEST_ITEM("Test get instances with predicate(Randomly)", testInstanceSelectors)
-        TEST_ITEM("Test get instances with predicate(testRandomByWeightSelector)", testRandomByWeightSelector)
         TEST_ITEM("Smoking test of ThreadLocal", testThreadLocal)
         TEST_ITEM("Smoking test of ThreadLocal(pointer)", testThreadLocalPtr)
         TEST_ITEM("Smoking test of ThreadLocal(pointer with initializer)", testThreadLocalPtrWithInitializer)
@@ -200,6 +201,7 @@ TEST_ITEM_START
         TEST_ITEM("Test delayed task pool - multiple tasks triggered at the same time", testDelayedThread2)
         TEST_ITEM("Register a service instance and remove it actively", testNamingServiceAndDeRegisterActively)
         TEST_ITEM("thread pool with concurrent add & atomic operation", testThreadPoolConcurrentWithAtomicCounter)
+        TEST_ITEM("Test sequence provider", testSequenceProvider)
 TEST_ITEM_END
 
 int main() {
diff --git a/test/testcase/testDelayedThreadPool.cpp b/test/testcase/testDelayedThreadPool.cpp
index 289322d..e4e0e13 100644
--- a/test/testcase/testDelayedThreadPool.cpp
+++ b/test/testcase/testDelayedThreadPool.cpp
@@ -29,7 +29,7 @@ class DelayedTask : public Task {
         if (executor == NULL) {
             throw NacosException(NacosException::INVALID_CONFIG_PARAM, "no executor");
         }
-        printf(">>>>>>>>>>>>>>>>>>Task %s triggered, time =%lu (%lu), interval = %lu\n", getTaskName().c_str(), now_ms/1000, now_ms, interval_calc);
+        printf(">>>>>>>>>>>>>>>>>>Task %s triggered, time =%llu (%llu), interval = %llu\n", getTaskName().c_str(), now_ms/1000, now_ms, interval_calc);
 
         sleep(1);
     }
diff --git a/test/testcase/testNamingService.cpp b/test/testcase/testNamingService.cpp
index e9806c3..952156e 100644
--- a/test/testcase/testNamingService.cpp
+++ b/test/testcase/testNamingService.cpp
@@ -71,8 +71,10 @@ bool testNamingProxySmokeTest() {
     for (int i = 0; i < 10; i++) {
         NacosString serviceName = "TestServiceName" + NacosStringOps::valueOf(i);
         NacosString serverlist = namingProxy->queryList(serviceName, ConfigConstant::DEFAULT_GROUP, "TestCluster", 0, false);
-
-        if (serverlist.find("\"serviceName\":\"" + serviceName + "\"") == string::npos) {
+        cout << serverlist << endl;
+        if (serverlist.find("\"serviceName\":\"" + serviceName + "\"") == string::npos &&
+            //nacos 2.x compatibility
+            serverlist.find("\"serviceName\":\"DEFAULT_GROUP@@" + serviceName + "\"") == string::npos) {
             cout << "Failed to get data for:" << serviceName << endl;
             return false;
         }
diff --git a/test/testcase/testSequenceProvider.cpp b/test/testcase/testSequenceProvider.cpp
new file mode 100644
index 0000000..ef5948e
--- /dev/null
+++ b/test/testcase/testSequenceProvider.cpp
@@ -0,0 +1,58 @@
+#include <iostream>
+#include "src/thread/Thread.h"
+#include "src/utils/SequenceProvider.h"
+#include "utils/DirUtils.h"
+
+using namespace std;
+using namespace nacos;
+
+#define NR_THREADS 200
+#define GENERATION_PER_THREAD 1000
+
+int64_t sequences[GENERATION_PER_THREAD * NR_THREADS];
+int tid[NR_THREADS];
+
+SequenceProvider<uint64_t> *sequenceProvider;
+
+void *SeqThreadFunc(void *param) {
+    int *thread_no = (int*)param;
+    for (int i = 0; i < GENERATION_PER_THREAD; i++) {
+        int64_t res = sequenceProvider->next();
+        sequences[(*thread_no) * GENERATION_PER_THREAD + i] = res;
+    }
+
+    return NULL;
+}
+
+bool testSequenceProvider() {
+    cout << "in function testSequenceProvider" << endl;
+
+    cout << "Generating SEQ..." << endl;
+
+    sequenceProvider = new SequenceProvider<uint64_t> (DirUtils::getCwd() + "/test_seq.dat", 20000, 100);
+
+    Thread *threads[NR_THREADS] = {NULL};
+    for (int i = 0; i < NR_THREADS; i++) {
+        NacosString threadName = "SEQThread-" + NacosStringOps::valueOf(i);
+        tid[i] = i;
+        threads[i] = new Thread(threadName, SeqThreadFunc, (void *) &tid[i]);
+        threads[i]->start();
+    }
+
+    for (int i = 0; i < NR_THREADS; i++) {
+        threads[i]->join();
+        delete threads[i];
+    }
+
+    cout << "Generated." << endl;
+
+    for (int i = 0; i < NR_THREADS; i++) {
+        for (int j = 0; j < GENERATION_PER_THREAD; j++) {
+            cout << "Thread " << i << ": sequence =\t" << sequences[i * GENERATION_PER_THREAD + j] << endl;
+        }
+    }
+
+    cout << "test end..." << endl;
+
+    return true;
+}
diff --git a/test/testcase/testThreadSmoke.cpp b/test/testcase/testThreadSmoke.cpp
index 0d52aac..8021eba 100644
--- a/test/testcase/testThreadSmoke.cpp
+++ b/test/testcase/testThreadSmoke.cpp
@@ -82,13 +82,13 @@ bool testThreadPoolSmoke() {
     return true;
 }
 
-AtomicInt totalFinishedThreads;
+AtomicInt<int> totalFinishedThreads;
 
 class SmokingTestThreadTask : public Task {
 private:
-    AtomicInt &_counter;
+    AtomicInt<int> &_counter;
 public:
-    SmokingTestThreadTask(const NacosString &taskName, AtomicInt &counter) : _counter(counter) {
+    SmokingTestThreadTask(const NacosString &taskName, AtomicInt<int> &counter) : _counter(counter) {
         setTaskName(taskName);
     };
 
@@ -108,7 +108,7 @@ bool testThreadPoolConcurrentWithAtomicCounter() {
     ThreadPool tp(10);
     tp.start();
     cout << "ok, size = 10" << endl;
-    AtomicInt totalCounter;
+    AtomicInt<int> totalCounter;
 
     Task *tasks[1000];
     for (size_t i = 0; i < 40; i++) {