Titile: a command line shell to read/write data from a leveldb thrift server

Summary: implemented a commond line shell to talk with leveldb thrift server, which is based on state pattern and can be easily extended.

Test Plan: build and run

Reviewers: dhruba, zshao, heyongqiang

Differential Revision: https://reviews.facebook.net/D4713

Makefile

@@ -21,7 +21,7 @@ $(shell ./build_detect_platform build_config.mk)
 # this file is generated by the previous line to set build flags and sources
 include build_config.mk
 
-CFLAGS += -I. -I./include  $(PLATFORM_CCFLAGS) $(OPT)
+CFLAGS += -I. -I./include $(PLATFORM_CCFLAGS) $(OPT)
 CXXFLAGS += -I. -I./include $(PLATFORM_CXXFLAGS) $(OPT)
 
 LDFLAGS += $(PLATFORM_LDFLAGS)
@@ -33,6 +33,9 @@ MEMENVOBJECTS = $(MEMENV_SOURCES:.cc=.o)
 TESTUTIL = ./util/testutil.o
 TESTHARNESS = ./util/testharness.o $(TESTUTIL)
 
+TOOLS = \
+	leveldb_shell
+
 TESTS = \
 	arena_test \
 	bloom_test \
@@ -52,8 +55,7 @@ TESTS = \
 	table_test \
 	version_edit_test \
 	version_set_test \
-	write_batch_test \
-        leveldb_server_test
+	write_batch_test
 
 PROGRAMS = db_bench $(TESTS)
 BENCHMARKS = db_bench_sqlite3 db_bench_tree_db
@@ -80,7 +82,7 @@ $(SHARED1): $(SHARED3)
 	ln -fs $(SHARED3) $(SHARED1)
 endif
 
-all: $(SHARED) $(LIBRARY) $(THRIFTSERVER)
+all: $(SHARED) $(LIBRARY) $(THRIFTSERVER) $(TOOLS)
 
 check: all $(PROGRAMS) $(TESTS)
 	for t in $(TESTS); do echo "***** Running $$t"; ./$$t || exit 1; done
@@ -93,6 +95,9 @@ $(LIBRARY): $(LIBOBJECTS)
 	rm -f $@
 	$(AR) -rs $@ $(LIBOBJECTS)
 
+leveldb_shell: tools/shell/ShellContext.o tools/shell/ShellState.o tools/shell/LeveldbShell.o tools/shell/DBClientProxy.o tools/shell/ShellContext.h tools/shell/ShellState.h tools/shell/DBClientProxy.h $(LIBOBJECTS)
+	$(CXX) tools/shell/ShellContext.o tools/shell/ShellState.o tools/shell/LeveldbShell.o tools/shell/DBClientProxy.o $(LIBOBJECTS) -o $@ $(LDFLAGS)
+
 db_bench: db/db_bench.o $(LIBOBJECTS) $(TESTUTIL)
 	$(CXX) db/db_bench.o $(LIBOBJECTS) $(TESTUTIL) $(EXEC_LDFLAGS) -o $@  $(LDFLAGS)
 
@@ -169,6 +174,9 @@ leveldb_server: thrift/server.o $(LIBRARY)
 leveldb_server_test: thrift/test/simpletest.o $(LIBRARY) 
 	$(CXX) thrift/test/simpletest.o $(LIBRARY) $(EXEC_LDFLAGS) -o $@  $(LDFLAGS)
 
+DBClientProxy_test: tools/shell/test/DBClientProxyTest.o tools/shell/DBClientProxy.o $(LIBRARY) 
+	$(CXX) tools/shell/test/DBClientProxyTest.o tools/shell/DBClientProxy.o $(LIBRARY) $(EXEC_LDFLAGS) -o $@  $(LDFLAGS)
+
 ifeq ($(PLATFORM), IOS)
 # For iOS, create universal object files to be used on both the simulator and
 # a device.

tools/shell/DBClientProxy.cpp

@@ -0,0 +1,271 @@
+
+#include <boost/shared_ptr.hpp>
+
+#include "DBClientProxy.h"
+
+
+#include "thrift/lib/cpp/protocol/TBinaryProtocol.h"
+#include "thrift/lib/cpp/transport/TSocket.h"
+#include "thrift/lib/cpp/transport/TTransportUtils.h"
+
+
+
+using namespace std;
+using namespace boost;
+using namespace Tleveldb;
+using namespace apache::thrift::protocol;
+using namespace apache::thrift::transport;
+
+namespace leveldb {
+
+DBClientProxy::DBClientProxy(const string & host, int port) :
+  host_(host),
+  port_(port),
+  dbToHandle_(),
+  dbClient_() {
+}
+
+DBClientProxy::~DBClientProxy() {
+  cleanUp();
+}
+
+
+void DBClientProxy::connect(void) {
+  cleanUp();
+  printf("Connecting to %s:%d\n", host_.c_str(), port_);
+  try {
+    boost::shared_ptr<TSocket> socket(new TSocket(host_, port_));
+    boost::shared_ptr<TTransport> transport(new TBufferedTransport(socket));
+    boost::shared_ptr<TBinaryProtocol> protocol(new TBinaryProtocol(transport));
+    dbClient_.reset(new DBClient(protocol));
+
+    transport->open();
+  } catch (const std::exception & e) {
+    dbClient_.reset();
+    throw;
+  }
+}
+
+void DBClientProxy::cleanUp(void) {
+  if(dbClient_.get()) {
+    for(map<string, DBHandle>::iterator itor = dbToHandle_.begin();
+        itor != dbToHandle_.end();
+        ++itor) {
+      dbClient_->Close(itor->second, itor->first);
+    }
+    dbClient_.reset();
+  }
+  dbToHandle_.clear();
+}
+
+void DBClientProxy::open(const string & db) {
+  if(!dbClient_.get()) {
+    printf("please connect() first\n");
+    return;
+  }
+
+  //  printf("opening database : %s\n", db.c_str());
+  // we use default DBOptions here
+  DBOptions opt;
+  DBHandle handle;
+  try {
+    dbClient_->Open(handle, db, opt);
+  } catch (const LeveldbException & e) {
+    printf("%s\n", e.message.c_str());
+    if(kIOError == e.errorCode) {
+      printf("no such database : %s\n", db.c_str());
+      return;
+    }else {
+      printf("Unknown error : %d\n", e.errorCode);
+      return;
+    }
+  }
+
+  dbToHandle_[db] = handle;
+}
+
+
+bool DBClientProxy::create(const string & db) {
+  if(!dbClient_.get()) {
+    printf("please connect() first\n");
+    return false;
+  }
+
+  printf("creating database : %s\n", db.c_str());
+  DBOptions opt;
+  opt.create_if_missing = true;
+  opt.error_if_exists = true;
+  DBHandle handle;
+  try {
+    dbClient_->Open(handle, db, opt);
+  }catch (const LeveldbException & e) {
+    printf("%s\n", e.message.c_str());
+    printf("error code : %d\n", e.errorCode);
+    if(kNotFound == e.errorCode) {
+      printf("no such database : %s\n", db.c_str());
+      return false;;
+    } else {
+      printf("Unknown error : %d\n", e.errorCode);
+      return false;
+    }
+  }
+
+  dbToHandle_[db] = handle;
+  return true;
+}
+
+
+map<string, DBHandle>::iterator
+DBClientProxy::getHandle(const string & db) {
+  map<string, DBHandle>::iterator itor = dbToHandle_.find(db);
+  if(dbToHandle_.end() == itor) {
+    open(db);
+    itor = dbToHandle_.find(db);
+  }
+
+  return itor;
+}
+
+
+bool DBClientProxy::get(const string & db,
+                        const string & key,
+                        string & value) {
+  if(!dbClient_.get()) {
+    printf("please connect() first\n");
+    return false;
+  }
+
+  map<string, DBHandle>::iterator itor = getHandle(db);
+  if(dbToHandle_.end() == itor) {
+    return false;
+  }
+
+  ResultItem ret;
+  Slice k;
+  k.data = key;
+  k.size = key.size();
+  // we use default values of options here
+  ReadOptions opt;
+  dbClient_->Get(ret,
+                 itor->second,
+                 k,
+                 opt);
+  if(kOk == ret.status) {
+    value = ret.value.data;
+    return true;
+  } else if(kNotFound == ret.status) {
+    printf("no such key : %s\n", key.c_str());
+    return false;
+  } else {
+    printf("get data error : %d\n", ret.status);
+    return false;
+  }
+}
+
+
+
+bool DBClientProxy::put(const string & db,
+                        const string & key,
+                        const string & value) {
+  if(!dbClient_.get()) {
+    printf("please connect() first\n");
+    return false;
+  }
+
+  map<string, DBHandle>::iterator itor = getHandle(db);
+  if(dbToHandle_.end() == itor) {
+    return false;
+  }
+ 
+  kv temp;
+  temp.key.data = key;
+  temp.key.size = key.size();
+  temp.value.data = value;
+  temp.value.size = value.size();
+  WriteOptions opt;
+  opt.sync = true;
+  Code code;
+  code = dbClient_->Put(itor->second,
+                        temp,
+                        opt);
+
+
+  if(kOk == code) {
+    //    printf("set value finished\n");
+    return true;
+  } else {
+    printf("put data error : %d\n", code);
+    return false;
+  }
+}
+
+bool DBClientProxy::scan(const string & db,
+                         const string & start_key,
+                         const string & end_key,
+                         const string & limit,
+                         vector<pair<string, string> > & kvs) {
+  if(!dbClient_.get()) {
+    printf("please connect() first\n");
+    return false;
+  }
+
+  int limitInt = -1;
+  limitInt = atoi(limit.c_str());
+  if(limitInt <= 0) {
+    printf("Error while parse limit : %s\n", limit.c_str());
+    return false;
+  }
+
+  if(start_key > end_key) {
+    printf("empty range.\n");
+    return false;
+  }
+
+  map<string, DBHandle>::iterator itor = getHandle(db);
+  if(dbToHandle_.end() == itor) {
+    return false;
+  }
+
+  ResultIterator ret;
+  // we use the default values of options here
+  ReadOptions opt;
+  Slice k;
+  k.data = start_key;
+  k.size = start_key.size();
+  dbClient_->NewIterator(ret,
+                         itor->second,
+                         opt,
+                         seekToKey,
+                         k);
+  Iterator it;
+  if(kOk == ret.status) {
+    it = ret.iterator;
+  } else {
+    printf("get iterator error : %d\n", ret.status);
+    return false;
+  }
+
+  int idx = 0;
+  string ck = start_key;
+  while(idx < limitInt && ck < end_key) {
+    ResultPair retPair;
+    dbClient_->GetNext(retPair, itor->second, it);
+    if(kOk == retPair.status) {
+      ++idx;
+      ck = retPair.keyvalue.key.data;
+      if (ck < end_key) {
+        kvs.push_back(make_pair(retPair.keyvalue.key.data,
+                                retPair.keyvalue.value.data));
+      }
+    } else if(kEnd == retPair.status) {
+      printf("not enough values\n");
+      return true;
+    } else {
+      printf("GetNext() error : %d\n", retPair.status);
+      return false;
+    }
+  }
+  return true;
+}
+
+} // namespace

tools/shell/DBClientProxy.h

@@ -0,0 +1,64 @@
+
+#ifndef TOOLS_SHELL_DBCLIENTPROXY
+#define TOOLS_SHELL_DBCLIENTPROXY
+
+#include <vector>
+#include <map>
+#include <string>
+#include <boost/utility.hpp>
+#include <boost/shared_ptr.hpp>
+
+#include "DB.h"
+
+/*
+ * class DBClientProxy maintains:
+ * 1. a connection to leveldb service
+ * 2. a map from db names to opened db handles
+ *
+ * it's client codes' responsibility to catch all possible exceptions.
+ */
+
+namespace leveldb {
+
+class DBClientProxy : private boost::noncopyable {
+ public:
+  // connect to host_:port_
+  void connect(void);
+
+  // return true on success, false otherwise
+  bool get(const std::string & db,
+           const std::string & key,
+           std::string & value);
+
+  // return true on success, false otherwise
+  bool put(const std::string & db,
+           const std::string & key,
+           const std::string & value);
+
+  // return true on success, false otherwise
+  bool scan(const std::string & db,
+            const std::string & start_key,
+            const std::string & end_key,
+            const std::string & limit,
+            std::vector<std::pair<std::string, std::string> > & kvs);
+
+  // return true on success, false otherwise
+  bool create(const std::string & db);
+
+  DBClientProxy(const std::string & host, int port);
+  ~DBClientProxy();
+
+ private:
+  // some internal help functions
+  void cleanUp(void);
+  void open(const std::string & db);
+  std::map<std::string, Tleveldb::DBHandle>::iterator getHandle(const std::string & db);
+
+  const std::string host_;
+  const int port_;
+  std::map<std::string, Tleveldb::DBHandle> dbToHandle_;
+  boost::shared_ptr<Tleveldb::DBClient> dbClient_;
+};
+
+} // namespace
+#endif

tools/shell/LeveldbShell.cpp

@@ -0,0 +1,8 @@
+
+
+#include "ShellContext.h"
+
+int main(int argc, char ** argv) {
+  ShellContext c(argc, argv);
+  c.run();
+}

tools/shell/ShellContext.cpp

@@ -0,0 +1,104 @@
+
+#include <iostream>
+#include <boost/shared_ptr.hpp>
+
+#include "ShellContext.h"
+#include "ShellState.h"
+
+
+
+#include "thrift/lib/cpp/protocol/TBinaryProtocol.h"
+#include "thrift/lib/cpp/transport/TSocket.h"
+#include "thrift/lib/cpp/transport/TTransportUtils.h"
+
+
+
+using namespace std;
+using namespace boost;
+using namespace Tleveldb;
+using namespace leveldb;
+using namespace apache::thrift::protocol;
+using namespace apache::thrift::transport;
+
+void ShellContext::changeState(ShellState * pState) {
+  pShellState_ = pState;
+}
+
+void ShellContext::stop(void) {
+  exit_ = true;
+}
+
+bool ShellContext::ParseInput(void) {
+  if(argc_ != 3) {
+    printf("leveldb_shell host port\n");
+    return false;
+  }
+
+  port_ = atoi(argv_[2]);
+  if(port_ <= 0) {
+    printf("Error while parse port : %s\n", argv_[2]);
+    return false;
+  }
+
+  clientProxy_.reset(new DBClientProxy(argv_[1], port_));
+  if(!clientProxy_.get()) {
+    return false;
+  } else {
+    return true;
+  }
+}
+
+void ShellContext::connect(void) {
+  clientProxy_->connect();
+}
+
+void ShellContext::create(const string & db) {
+  if (clientProxy_->create(db)) {
+    printf("%s created\n", db.c_str());
+  }
+}
+
+void ShellContext::get(const string & db,
+                       const string & key) {
+  string v;
+  if (clientProxy_->get(db, key, v)) {
+    printf("%s\n", v.c_str());
+  }
+}
+
+void ShellContext::put(const string & db,
+                       const string & key,
+                       const string & value) {
+  if (clientProxy_->put(db, key, value)) {
+    printf("(%s, %s) has been set\n", key.c_str(), value.c_str());
+  }
+}
+
+void ShellContext::scan(const string & db,
+                        const string & start_key,
+                        const string & end_key,
+                        const string & limit) {
+  vector<pair<string, string> > kvs;
+  if (clientProxy_->scan(db, start_key, end_key, limit, kvs)) {
+    for(unsigned int i = 0; i < kvs.size(); ++i) {
+      printf("%d (%s, %s)\n", i, kvs[i].first.c_str(), kvs[i].second.c_str());
+    }
+  }
+}
+
+void ShellContext::run(void) {
+  while(!exit_) {
+    pShellState_->run(this);
+  }
+}
+
+ShellContext::ShellContext(int argc, char ** argv) :
+  pShellState_(ShellStateStart::getInstance()),
+  exit_(false),
+  argc_(argc),
+  argv_(argv),
+  port_(-1),
+  clientProxy_() {
+}
+
+

tools/shell/ShellContext.h

@@ -0,0 +1,51 @@
+#ifndef TOOLS_SHELL_SHELLCONTEXT
+#define TOOLS_SHELL_SHELLCONTEXT
+
+#include <map>
+#include <string>
+#include <boost/utility.hpp>
+#include <boost/shared_ptr.hpp>
+
+#include "DB.h"
+#include "DBClientProxy.h"
+
+class ShellState;
+
+class ShellContext : private boost::noncopyable {
+ public:
+  void changeState(ShellState * pState);
+
+  void stop(void);
+
+  bool ParseInput(void);
+
+  void connect(void);
+
+  void get(const std::string & db,
+           const std::string & key);
+
+  void put(const std::string & db,
+           const std::string & key,
+           const std::string & value);
+
+  void scan(const std::string & db,
+            const std::string & start_key,
+            const std::string & end_key,
+            const std::string & limit);
+
+  void create(const std::string & db);
+
+  void run(void);
+
+  ShellContext(int argc, char ** argv);
+
+ private:
+  ShellState * pShellState_;
+  bool exit_;
+  int argc_;
+  char ** argv_;
+  int port_;
+  boost::shared_ptr<leveldb::DBClientProxy> clientProxy_;
+};
+
+#endif

tools/shell/ShellState.cpp

@@ -0,0 +1,139 @@
+#include <iostream>
+#include <string>
+#include <sstream>
+#include <vector>
+
+#include "ShellState.h"
+#include "ShellContext.h"
+#include "transport/TTransportException.h"
+
+using namespace std;
+
+using namespace apache::thrift::transport;
+
+const char * PMT = ">> ";
+
+
+void ShellStateStart::run(ShellContext * c) {
+  if(!c->ParseInput()) {
+    c->changeState(ShellStateStop::getInstance());
+  } else {
+    c->changeState(ShellStateConnecting::getInstance());
+  }
+}
+
+
+void ShellStateStop::run(ShellContext * c) {
+  c->stop();
+}
+
+void ShellStateConnecting::run(ShellContext * c) {
+  try {
+    c->connect();
+  } catch (const TTransportException & e) {
+    cout << e.what() << endl;
+    c->changeState(ShellStateStop::getInstance());
+    return;
+  }
+  
+  c->changeState(ShellStateConnected::getInstance());
+}
+
+void ShellStateConnected::unknownCmd(void) {
+  cout << "Unknown command!" << endl;
+  cout << "Use help to list all available commands" << endl;
+}
+
+void ShellStateConnected::helpMsg(void) {
+  cout << "Currently supported commands:" << endl;
+  cout << "create db" << endl;
+  cout << "get db key" << endl;
+  cout << "scan db start_key end_key limit" << endl;
+  cout << "put db key value" << endl;
+  cout << "exit/quit" << endl;
+}
+
+void ShellStateConnected::handleConError(ShellContext * c) {
+  cout << "Connection down" << endl;
+  cout << "Reconnect ? (y/n) :" << endl;
+  string s;
+  while(getline(cin, s)) {
+    if("y" == s) {
+      c->changeState(ShellStateConnecting::getInstance());
+      break;
+    } else if("n" == s) {
+      c->changeState(ShellStateStop::getInstance());
+      break;
+    } else {
+      cout << "Reconnect ? (y/n) :" << endl;
+    }
+  }
+}
+
+void ShellStateConnected::run(ShellContext * c) {
+  string line;
+  cout << PMT;
+  getline(cin, line);
+  istringstream is(line);
+  vector<string> params;
+  string param;
+  while(is >> param) {
+    params.push_back(param);
+  }
+
+  // empty input line
+  if(params.empty())
+    return;
+
+  if("quit" == params[0] || "exit" == params[0]) {
+    c->changeState(ShellStateStop::getInstance());
+  } else if("get" == params[0]) {
+    if(params.size() == 3) {
+      try {
+        c->get(params[1], params[2]);
+      } catch (const TTransportException & e) {
+        cout << e.what() << endl;
+        handleConError(c);
+      }
+    } else {
+      unknownCmd();
+    }
+  } else if("create" == params[0]) {
+    if(params.size() == 2) {
+      try {
+        c->create(params[1]);
+      } catch (const TTransportException & e) {
+        cout << e.what() << endl;
+        handleConError(c);
+      }
+    } else {
+      unknownCmd();
+    }
+  }else if("put" == params[0]) {
+    if(params.size() == 4) {
+      try {
+        c->put(params[1], params[2], params[3]);
+      } catch (const TTransportException & e) {
+        cout << e.what() << endl;
+        handleConError(c);
+      }
+    } else {
+      unknownCmd();
+    }
+  } else if("scan" == params[0]) {
+    if(params.size() == 5) {
+      try {
+        c->scan(params[1], params[2], params[3], params[4]);
+      } catch (const TTransportException & e) {
+        cout << e.what() << endl;
+        handleConError(c);
+      }
+    } else {
+      unknownCmd();
+    }
+  } else if("help" == params[0]) {
+    helpMsg();
+  } else {
+    unknownCmd();
+  }
+}

tools/shell/ShellState.h

@@ -0,0 +1,87 @@
+
+#ifndef TOOLS_SHELL_SHELLSTATE
+#define TOOLS_SHELL_SHELLSTATE
+
+class ShellContext;
+
+/*
+ * Currently, there are four types of state in total
+ * 1. start state: the first state the program enters
+ * 2. connecting state: the program try to connnect to a leveldb server, whose
+ *    previous states could be "start" or "connected" states
+ * 3. connected states: the program has already connected to a server, and is
+ *    processing user commands
+ * 4. stop state: the last state the program enters, do some cleanning up things
+ */
+
+class ShellState {
+ public:
+  virtual void run(ShellContext *) = 0;
+  virtual ~ShellState() {}
+};
+
+
+class ShellStateStart : public ShellState {
+ public:
+  static ShellStateStart * getInstance(void) {
+    static ShellStateStart instance;
+    return &instance;
+  }
+
+  virtual void run(ShellContext *);
+
+ private:
+  ShellStateStart() {}
+  virtual ~ShellStateStart() {}
+};
+
+class ShellStateStop : public ShellState {
+ public:
+  static ShellStateStop * getInstance(void) {
+    static ShellStateStop instance;
+    return &instance;
+  }
+
+  virtual void run(ShellContext *);
+
+ private:
+  ShellStateStop() {}
+  virtual ~ShellStateStop() {}
+
+};
+
+class ShellStateConnecting : public ShellState {
+ public:
+  static ShellStateConnecting * getInstance(void) {
+    static ShellStateConnecting instance;
+    return &instance;
+  }
+
+  virtual void run(ShellContext *);
+
+ private:
+  ShellStateConnecting() {}
+  virtual ~ShellStateConnecting() {}
+
+};
+
+class ShellStateConnected : public ShellState {
+ public:
+  static ShellStateConnected * getInstance(void) {
+    static ShellStateConnected instance;
+    return &instance;
+  }
+
+  virtual void run(ShellContext *);
+
+ private:
+  ShellStateConnected() {}
+  virtual ~ShellStateConnected() {}
+
+  void unknownCmd();
+  void handleConError(ShellContext *);
+  void helpMsg();
+};
+
+#endif
+

tools/shell/test/DBClientProxyTest.cpp

@@ -0,0 +1,182 @@
+/**
+ * Tests for DBClientProxy class for leveldb
+ * @author Bo Liu (newpoo.liu@gmail.com)
+ * Copyright 2012 Facebook
+ */
+
+#include <algorithm>
+#include <vector>
+#include <string>
+#include <protocol/TBinaryProtocol.h>
+#include <transport/TSocket.h>
+#include <transport/TBufferTransports.h>
+#include <util/testharness.h>
+#include <DB.h>
+#include <AssocService.h>
+#include <leveldb_types.h>
+
+#include "server_options.h"
+
+
+#include "../DBClientProxy.h"
+using namespace leveldb;
+
+
+using namespace apache::thrift;
+using namespace apache::thrift::protocol;
+using namespace apache::thrift::transport;
+using boost::shared_ptr;
+using namespace Tleveldb;
+using namespace std;
+
+
+
+extern "C" void startServer(int argc, char**argv);
+extern "C" void stopServer(int port);
+extern  ServerOptions server_options;
+
+static const string db1("db1");
+
+
+static void testDBClientProxy(DBClientProxy & dbcp) {
+  bool flag;
+  const int NOK = 100;
+  const int BUFSIZE = 16;
+  int testcase = 0;
+
+  vector<string> keys, values;
+  vector<pair<string, string> > kvs, correctKvs;
+  string k, v;
+
+  for(int i = 0; i < NOK; ++i) {
+    char bufKey[BUFSIZE];
+    char bufValue[BUFSIZE];
+    snprintf(bufKey, BUFSIZE, "key%d", i);
+    snprintf(bufValue, BUFSIZE, "value%d", i);
+    keys.push_back(bufKey);
+    values.push_back(bufValue);
+    correctKvs.push_back((make_pair(string(bufKey), string(bufValue))));
+  }
+
+  sort(correctKvs.begin(), correctKvs.end());
+
+
+  // can not do get(), put(), scan() or create() before connected.
+  flag = dbcp.get(db1, keys[0], v);
+  ASSERT_TRUE(false == flag);
+  printf("\033[01;40;32mTEST CASE %d passed\033[01;40;37m\n", ++testcase);
+  flag = dbcp.put(db1, keys[0], keys[1]);
+  ASSERT_TRUE(false == flag);
+  printf("\033[01;40;32mTEST CASE %d passed\033[01;40;37m\n", ++testcase);
+  flag = dbcp.scan(db1, "a", "w", "100", kvs);
+  ASSERT_TRUE(false == flag);
+  printf("\033[01;40;32mTEST CASE %d passed\033[01;40;37m\n", ++testcase);
+  flag = dbcp.create(db1);
+  ASSERT_TRUE(false == flag);
+  printf("\033[01;40;32mTEST CASE %d passed\033[01;40;37m\n", ++testcase);
+
+  dbcp.connect();
+
+  // create a database
+  flag = dbcp.create(db1);
+  ASSERT_TRUE(true == flag);
+  printf("\033[01;40;32mTEST CASE %d passed\033[01;40;37m\n", ++testcase);
+
+  // no such key
+  flag = dbcp.get(db1, keys[0], v);
+  ASSERT_TRUE(false == flag);
+  printf("\033[01;40;32mTEST CASE %d passed\033[01;40;37m\n", ++testcase);
+
+
+  // scan() success with empty returned key-value pairs
+  kvs.clear();
+  flag = dbcp.scan(db1, "a", "w", "100", kvs);
+  ASSERT_TRUE(true == flag);
+  ASSERT_TRUE(kvs.empty());
+  printf("\033[01;40;32mTEST CASE %d passed\033[01;40;37m\n", ++testcase);
+
+
+  // put()
+  for(int i = 0; i < NOK; ++i) {
+    flag = dbcp.put(db1, keys[i], values[i]);
+    ASSERT_TRUE(true == flag);
+  }
+  printf("\033[01;40;32mTEST CASE %d passed\033[01;40;37m\n", ++testcase);
+
+
+  // scan all of key-value pairs
+  kvs.clear();
+  flag = dbcp.scan(db1, "a", "w", "100", kvs);
+  ASSERT_TRUE(true == flag);
+  ASSERT_TRUE(kvs == correctKvs);
+  printf("\033[01;40;32mTEST CASE %d passed\033[01;40;37m\n", ++testcase);
+
+
+  // scan the first 20 key-value pairs
+  {
+    kvs.clear();
+    flag = dbcp.scan(db1, "a", "w", "20", kvs);
+    ASSERT_TRUE(true == flag);
+    vector<pair<string, string> > tkvs(correctKvs.begin(), correctKvs.begin() + 20);
+    ASSERT_TRUE(kvs == tkvs);
+    printf("\033[01;40;32mTEST CASE %d passed\033[01;40;37m\n", ++testcase);
+  }
+
+  // scan key[10] to key[50]
+  {
+    kvs.clear();
+    flag = dbcp.scan(db1, correctKvs[10].first, correctKvs[50].first, "100", kvs);
+    ASSERT_TRUE(true == flag);
+
+    vector<pair<string, string> > tkvs(correctKvs.begin() + 10, correctKvs.begin() + 50);
+    ASSERT_TRUE(kvs == tkvs);
+    printf("\033[01;40;32mTEST CASE %d passed\033[01;40;37m\n", ++testcase);
+  }
+
+  // scan "key10" to "key40" by limit constraint
+  {
+    kvs.clear();
+    flag = dbcp.scan(db1, correctKvs[10].first.c_str(), "w", "30", kvs);
+    ASSERT_TRUE(true == flag);
+    vector<pair<string, string> > tkvs(correctKvs.begin() + 10, correctKvs.begin() + 40);
+    ASSERT_TRUE(kvs == tkvs);
+    printf("\033[01;40;32mTEST CASE %d passed\033[01;40;37m\n", ++testcase);
+  }
+
+
+  // get()
+  flag = dbcp.get(db1, "unknownKey", v);
+  ASSERT_TRUE(false == flag);
+  printf("\033[01;40;32mTEST CASE %d passed\033[01;40;37m\n", ++testcase);
+
+  flag = dbcp.get(db1, keys[0], v);
+  ASSERT_TRUE(true == flag);
+  ASSERT_TRUE(v == values[0]);
+  printf("\033[01;40;32mTEST CASE %d passed\033[01;40;37m\n", ++testcase);
+}
+
+
+
+static void cleanupDir(std::string dir) {
+  // remove old data, if any
+  char* cleanup = new char[100];
+  snprintf(cleanup, 100, "rm -rf %s", dir.c_str());
+  system(cleanup);
+}
+
+int main(int argc, char **argv) {
+  // create a server
+  startServer(argc, argv);
+  printf("Server thread created.\n");
+
+  // give some time to the server to initialize itself
+  while (server_options.getPort() == 0) {
+    sleep(1);
+  }
+
+  cleanupDir(server_options.getDataDirectory(db1));
+
+  DBClientProxy dbcp("localhost", server_options.getPort());
+  testDBClientProxy(dbcp);
+}
+