First round of refactoring of DCDBLib:

* Bumped Cassandra to 2.1.5
* Bumped cpp-driver to 2.0
* Eliminated cassandraBackend in favor of DCDBConnection

In the future, a DCDBConnection handles the low-level connection
to Cassandra. On top of an established DCDBConnection, you can
create a SensorDataStore object which gives you access to raw
sensor readings.

CollectAgent/collectagent.cpp

@@ -13,6 +13,7 @@
 
 #include <boost/date_time/posix_time/posix_time.hpp>
 
+#include <dcdb/connection.h>
 #include <dcdb/sensordatastore.h>
 
 #include "simplemqttserver.h"
@@ -175,7 +176,28 @@ int main(int argc, char* const argv[]) {
       }
 
       /*
-       * Allocate and initialize sensor data store.
+       * Allocate and initialize connection to Cassandra.
+       */
+      std::string sdHost(cassandraHost);
+      DCDBConnection dcdbConn(sdHost, 9042);
+
+      if (!dcdbConn.connect()) {
+          std::cout << "Cannot connect to Cassandra!" << std::endl;
+          exit(EXIT_FAILURE);
+      }
+
+      /*
+       * Legacy behavior: Initialize the DCDB schema in Cassandra.
+       */
+      dcdbConn.initSchema();
+
+      /*
+       * Allocate the SensorDataStore.
+       */
+      mySensorDataStore = new SensorDataStore(&dcdbConn);
+
+      /*
+       * Set TTL for data store inserts if TTL > 0.
        */
       uint64_t ttlInt;
       std::istringstream ttlParser(ttl);
@@ -183,8 +205,9 @@ int main(int argc, char* const argv[]) {
           std::cout << "Invalid TTL!" << std::endl;
           exit(EXIT_FAILURE);
       }
-      std::string sdHost(cassandraHost);
-      mySensorDataStore = new SensorDataStore(sdHost, 9042, ttlInt);
+      if (ttlInt) {
+        mySensorDataStore->setTTL(ttlInt);
+      }
 
       /*
        * Start the MQTT Message Server.
@@ -220,6 +243,7 @@ int main(int argc, char* const argv[]) {
 
       ms.stop();
       delete mySensorDataStore;
+      dcdbConn.disconnect();
   }
   catch (const exception& e) {
       cout << "Exception: " << e.what() << "\n";

DCDBLib/Makefile

@@ -6,8 +6,8 @@ CXXFLAGS = -O2 -ggdb -Wall -Werror -Wno-unused-local-typedefs -Wno-unknown-warni
 	-I$(DCDBBASEPATH)/include/ -fmessage-length=0 -DBOOST_DATE_TIME_POSIX_TIME_STD_CONFIG
 
 # List of object files to build and the derived list of corresponding source files
-OBJS = src/sensordatastore.o \
-       src/cassandraBackend.o \
+OBJS = src/connection.o \
+       src/sensordatastore.o \
        src/timestamp.o
 
 # List of public header files necessary to use this libray

DCDBLib/include/connection.h

+/*
+ * connection.h
+ *
+ *  Created on: May 18, 2015
+ *      Author: Axel Auweter
+ */
+
+/**
+ * @file
+ * @brief This file contains parts of the public API for the
+ * DCDBLib library.
+ * It contains the class definition of the DCDBConnection class,
+ * that handles connections to the data store and schema
+ * initialization.
+ */
+
+#include <string>
+#include <cstdint>
+
+#include "cassandra.h"
+
+#ifndef CONNECTION_H
+#define CONNECTION_H
+
+/* Forward-declaration of the implementation-internal classes */
+class DCDBConnectionImpl;
+
+class DCDBConnection
+{
+private:
+  DCDBConnectionImpl* impl;     /**< The object which implements the core functionality of this class */
+
+public:
+  /**
+   * @brief This function prints Cassandra CQL-specific
+   *        error messages from a CassFuture object.
+   * @param future  The future object which caused the error.
+   *
+   * @details
+   * Once a request to Cassandra completes, we get a CassFuture
+   * object which holds the return to our request. In case the
+   * request caused an error, this function prints a human-readable
+   * error message.
+   */
+  void printError(CassFuture* future);
+
+  /**
+   * @brief Set the hostname for the connection.
+   * @param hostname  Hostname of a Cassandra front end node.
+   */
+  void setHostname(std::string hostname);
+
+  /**
+   * @brief Return the current hostname of the connection.
+   * @return The hostname of a Cassandra front end node to which this object will connect.
+   */
+  std::string getHostname();
+
+  /**
+   * @brief Set the port for the connection.
+   * @param port  Port on which the Cassandra front end node accepts CQL native protocol clients.
+   */
+  void setPort(uint16_t port);
+
+  /**
+   * @brief Return the current port of the connection.
+   * @return The port on which the Cassandra front end node accepts CQL native protocol clients.
+   */
+  uint16_t getPort();
+
+  /**
+   * @brief Establish a connection to the Cassandra database.
+   * @return True if the connection was successfully established, false otherwise.
+   */
+  bool connect();
+
+  /**
+   * @brief Disconnect an existing connection to the Cassandra database.
+   */
+  void disconnect();
+
+  /**
+   * @brief Get the session handle of the connection.
+   * @return Pointer to this connection's session object.
+   */
+  CassSession* getSessionHandle();
+
+  /**
+   * @brief This function executes a simple raw CQL query.
+   * @param query  The CQL query string.
+   * @return       Returns a CassError type to indicate success or failure
+   */
+  CassError executeSimpleQuery(std::string query);
+
+  /**
+   * @brief Initialize the database schema for DCDB.
+   * @return True if the schema was successfully initialized.
+   */
+  bool initSchema();
+
+  DCDBConnection();
+  DCDBConnection(std::string hostname, uint16_t port);
+  virtual ~DCDBConnection();
+};
+
+#endif /* CONNECTION_H */

DCDBLib/include/sensordatastore.h

@@ -16,6 +16,8 @@
 #include <stdint.h>
 #include <string>
 
+#include "connection.h"
+
 #ifndef SENSORDATASTORE_H_
 #define SENSORDATASTORE_H_
 
@@ -97,16 +99,6 @@ private:
     CassandraBackend* csBackend;
     
 public:
-    /**
-     * @brief This function initializes the SensorDataStore object,
-     *        sets the connection parameters and established a
-     *        connection to the database.
-     * @param hostname The hostname or IP address of the database node to connect to.
-     * @param port     The port on which the database node is listening.
-     * @param ttl      The TTL for data inserted into the data store (set to 0 for unlimited)
-     */
-    void init(std::string hostname, int port, uint64_t ttl);
-
     /**
      * @brief This function populates a preallocated SensorId object
      *        from a MQTT topic string.
@@ -126,19 +118,17 @@ public:
     void insert(SensorId* sid, uint64_t ts, uint64_t value);
     
     /**
-     * @brief A shortcut constructor for a SensorDataStore object
-     *        that automatically initializes with default parameters
-     *        for hostname and port.
+     * @brief Set the TTL for newly inserted sensor data.
+     * @param ttl      The TTL for the sensor data in seconds.
      */
-    SensorDataStore();
+    void setTTL(uint64_t ttl);
 
     /**
-     * @brief The standard constructor for a SensorDataStore object.
-     * @param hostname A string containing the hostname or IP address of the database server.
-     * @param port     A integer containing the port number on which the database server is listening.
-     * @param ttl      A uint64_t containing the TTL for inserted data items.
+     * @brief A shortcut constructor for a SensorDataStore object
+     *        that allows accessing the data store through a
+     *        connection that is already established.
      */
-    SensorDataStore(std::string hostname, int port, uint64_t ttl);
+    SensorDataStore(DCDBConnection* conn);
 
     /**
      * @brief The standard destructor for a SensorDatStore object.

DCDBLib/include_internal/cassandraBackend.h → DCDBLib/include_internal/connection_internal.h

 /*
- * cassandraBackend.h
+ * connection_internal.h
  *
- *  Created on: Apr 08, 2013
+ *  Created on: May 18, 2015
  *      Author: Axel Auweter
  */
 
 /*
  * @file
- * @brief This file defines the CassandraBackend class and related
- *        things that provide a low-level abstraction to the
- *        Cassandra key-value store.
+ * @brief This file contains the internal functions of the
+ *        DCDBConnection which are provided by the
+ *        DCDBConnectionImpl class.
  */
 
-#ifndef CASSANDRA_BACKEND_H
-#define CASSANDRA_BACKEND_H
-
 #include <string>
+#include <cstdint>
 
-#include <dcdbendian.h>
+#include "connection.h"
 
-#include "cassandra.h"
+#ifndef CONNECTION_INTERNAL_H
+#define CONNECTION_INTERNAL_H
 
-/**
- * @brief The CassandraBackend class provides low-level
- *        access to the Cassandra key-value store using
- *        the CQL API.
- */
-class CassandraBackend
+class DCDBConnectionImpl
 {
 protected:
+  std::string hostname_;        /**< The hostname of a DB front-end node. */
+  uint16_t    port_;            /**< The port of the DB front-end node. */
+  bool        connected;        /**< Indicates whether a connection has been established. */
+
   CassCluster* cluster;         /**< The Cassandra Cluster object (contains hostname, port, etc) */
   CassSession* session;         /**< The session object through which we communicate with C* once the connection is established */
-  const CassSchema*  schema;    /**< The schema object containing the current database schema information */
+  const CassSchema* schema;     /**< The schema object containing the current database schema information */
   std::string  currentKeyspace; /**< The name of the active keyspace */
 
-  const CassPrepared* preparedInsert; /**< The prepared statement for insertions */
-
   /**
    * @brief This function validates a name to ensure that
    *        it only consists of alphanumeric characters.
@@ -44,39 +40,6 @@ protected:
    */
   bool validateName(std::string name);
 
-  /**
-   * @brief This function converts a uint64_t into a big-endian
-   *        byte array represented as std::string.
-   * @param n  The value to convert
-   * @return   The string containing the big-endian byte array.
-   */
-  std::string int64Convert(uint64_t n);
-
-  /**
-   * @brief This function prints Cassandra CQL-specific
-   *        error messages from a CassFuture object.
-   * @param future  The future object which caused the error.
-   */
-  void printError(CassFuture* future);
-
-  /**
-   * @brief This function executes a simple raw CQL query.
-   * @param query  The CQL query string.
-   * @return       Returns a CassError type to indicate success or failure
-   */
-  CassError executeSimpleQuery(std::string query);
-
-public:
-  /* Database meta operations */
-
-  /**
-   * @brief Starts a connection to a Cassandra front-end node.
-   * @param hostname   The hostname to connect to.
-   * @param port       The TCP port number on which Cassandra is listening for CQL clients.
-   * @return           Returns true if a connection was established, false otherwise.
-   */
-  bool connect(std::string hostname, int port);
-
   /**
    * @brief Fetch the list of Key Spaces from the Cassandra server.
    */
@@ -127,34 +90,59 @@ public:
   void createColumnFamily(std::string name, std::string fields, std::string primaryKey, std::string options);
 
 
-  /* Database data access operations */
+public:
+  /**
+   * @brief The implementation function of DCDBConnection::printError().
+   */
+  void printError(CassFuture* future);
 
   /**
-   * @brief Insert a data into the database
-   * @param key           The name of the row key
-   * @param ts            The data time stamp (used for column name and time information in Cassandra
-   * @param value         The data itself
+   * @brief The implementation function of DCDBConnection::setHostname().
    */
-  void insert(std::string key, uint64_t ts, uint64_t value);
+  void setHostname(std::string hostname);
 
   /**
-   * @brief Prepare for insertions
+   * @brief The implementation function of DCDBConnection::getHostname().
    */
-  void prepareInsert(uint64_t ttl);
+  std::string getHostname();
 
+  /**
+   * @brief The implementation function of DCDBConnection::setPort().
+   */
+  void setPort(uint16_t port);
 
-  /* Class constructor / desctructor */
+  /**
+   * @brief The implementation function of DCDBConnection::getPort().
+   */
+  uint16_t getPort();
 
   /**
-   * @brief The standard constructor for CassandraBackend
+   * @brief The implementation function of DCDBConnection::connect().
    */
-  CassandraBackend();
+  bool connect();
 
   /**
-   * @brief The standard desctructor for CassandraBackend
+   * @brief The implementation function of DCDBConnection::disconnect().
    */
-  virtual ~CassandraBackend();
-};
+  void disconnect();
+
+  /**
+   * @brief The implementation function of DCDBConnection::getSessionHandle().
+   */
+  CassSession* getSessionHandle();
+
+  /**
+   * @brief The implementation function of DCDBConnection::executeSimpleQuery().
+   */
+  CassError executeSimpleQuery(std::string query);
 
+  /**
+   * @brief The implementation function of DCDBConnection::initSchema().
+   */
+  bool initSchema();
+
+  DCDBConnectionImpl();
+  virtual ~DCDBConnectionImpl();
+};
 
-#endif /* CASSANDRA_BACKEND_H */
+#endif /* CONNECTION_INTERNAL_H */

DCDBLib/include_internal/dcdbglobals.h

+/*
+ * dcdbglobals.h
+ *
+ *  Created on: May 18, 2015
+ *      Author: Axel Auweter
+ */
+
+/**
+ * @file
+ * @brief This file contains some global definitions and names
+ * use by the DCDBLib library.
+ */
+
+#ifndef DCDB_GLOBALS_H
+#define DCDB_GLOBALS_H
+
+#define KEYSPACE_NAME        "dcdb"
+#define CF_SENSORDATA        "sensordata"
+
+#define CONFIG_KEYSPACE_NAME KEYSPACE_NAME "_config"
+#define CF_PUBLISHEDSENSORS  "publishedsensors"
+#define CF_VIRTUALSENSORS    "virtualsensors"
+
+#endif /* DCDB_GLOBALS_H */

DCDBLib/include_internal/sensordatastore_internal.h

@@ -18,14 +18,7 @@
 #include <string>
 
 #include "sensordatastore.h"
-#include "cassandraBackend.h"
-
-#define KEYSPACE_NAME        "dcdb"
-#define CF_SENSORDATA        "sensordata"
-
-#define CONFIG_KEYSPACE_NAME KEYSPACE_NAME "_config"
-#define CF_PUBLISHEDSENSORS  "publishedsensors"
-#define CF_VIRTUALSENSORS    "virtualsensors"
+#include "connection.h"
 
 /**
  * @brief The SensorDataStoreImpl class contains all protected
@@ -35,7 +28,9 @@
 class SensorDataStoreImpl
 {
 protected:
-  CassandraBackend* csBackend;    /**< The CassandraBackend object that does the low-level stuff for us. */
+  DCDBConnection*     connection;     /**< The DCDBCOnnection object that does the low-level stuff for us. */
+  CassSession*        session;        /**< The CassSession object given by the connection. */
+  const CassPrepared* preparedInsert; /**< The prepared statement for fast insertions. */
 
   /**
    * @brief This function returns a "key" string which
@@ -45,15 +40,13 @@ protected:
    */
   std::string sidConvert(SensorId *sid);
 
-public:
   /**
-   * @brief This function connects to the database and initializes keyspaces and column families
-   * @param hostname  The hostname of a Cassandra front-end node
-   * @param port      The port number of the Cassandra front-end node
-   * @param ttl       The TTL for inserted data (set to 0 to insert data without TTL)
+   * @brief Prepare for insertions.
+   * @param ttl   A TTL that will be set for newly inserted values. Set to 0 to insert without TTL.
    */
-  void init(std::string hostname, int port, uint64_t ttl);
+  void prepareInsert(uint64_t ttl);
 
+public:
   /**
    * @brief This function converts a MQTT topic string to a SensorId object
    * @param topic   The MQTT topic string to convert
@@ -69,11 +62,17 @@ public:
    */
   void insert(SensorId* sid, uint64_t ts, uint64_t value);
 
+  /**
+   * @brief This function sets the TTL of newly inserted readings.
+   * @param ttl    The TTL to be used for new inserts in seconds.
+   */
+  void setTTL(uint64_t ttl);
+
   /**
    * @brief This is the standard constructor of the SensorDataStoreImpl class.
    * @param csb   A CassandraBackend object to do the raw database access.
    */
-  SensorDataStoreImpl(CassandraBackend *csb);
+  SensorDataStoreImpl(DCDBConnection* conn);
 
   /**
    * @brief The standard desctructor of SensorDataStoreImpl.

DCDBLib/src/cassandraBackend.cpp → DCDBLib/src/connection.cpp

 /*
- * cassandraBackend.cpp
+ * connection.cpp
  *
- *  Created on: Apr 08, 2013
+ *  Created on: May 18, 2015
  *      Author: Axel Auweter
  */
 
+#include <algorithm>
 #include <iostream>
-#include <string>
 
 #include <boost/lexical_cast.hpp>
 
-#include <cstdio>
-#include <cstdlib>
-#include <cstdint>
-#include <cinttypes>
+#include "cassandra.h"
 
-#include "cassandraBackend.h"
+#include "connection.h"
+#include "connection_internal.h"
+#include "dcdbglobals.h"
 
-/**
- * @details
- * Once a request to Cassandra completes, we get a CassFuture
- * object which holds the return to our request. In case the
- * request caused an error, this function prints a human-readable
- * error message.
+/*
+ * Definition of the public DCDBConnection functions.
+ * All calls forward calls of all DCDBConnection functions
+ * to their counterparts in the DCDBConnectionImpl class.
  */
-void CassandraBackend::printError(CassFuture* future)
-{
-  CassString message = cass_future_error_message(future);
-  std::cerr << "Cassandra Backend Error: " << std::string(message.data, message.length) << std::endl;
+void DCDBConnection::printError(CassFuture* future) {
+  impl->printError(future);
 }
 
-/**
- * @details
- * The request is issued as a simple synchronous CQL statement.
- */
-CassError CassandraBackend::executeSimpleQuery(std::string query)
-{
-  CassError rc = CASS_OK;
-  CassFuture* future = NULL;
-  CassStatement* statement = cass_statement_new(cass_string_init(query.c_str()), 0);
+void DCDBConnection::setHostname(std::string hostname) {
+  impl->setHostname(hostname);
+}
 
-  future = cass_session_execute(session, statement);
-  cass_future_wait(future);
+std::string DCDBConnection::getHostname() {
+  return impl->getHostname();
+}
 
-  rc = cass_future_error_code(future);
-  if (rc != CASS_OK) {
-      printError(future);
-  }
+void DCDBConnection::setPort(uint16_t port) {
+  impl->setPort(port);
+}
 
-  cass_future_free(future);
-  cass_statement_free(statement);
+uint16_t DCDBConnection::getPort() {
+  return impl->getPort();
+}
 
-  return rc;
+bool DCDBConnection::connect() {
+  return impl->connect();
 }
 
+void DCDBConnection::disconnect() {
+  impl->disconnect();
+}
 
-/**
- * @details
- * This function connects to a Cassandra front end node
- * using the CQL API.
+bool DCDBConnection::initSchema() {
+  return impl->initSchema();
+}
+
+CassSession* DCDBConnection::getSessionHandle() {
+  return impl->getSessionHandle();
+}
+
+/*
+ * DCDBConnection constructors & destructor.
+ * Upon object creation, allocate a corresponding impl class
+ * and free it on object deallocation.
  */
-bool CassandraBackend::connect(std::string hostname, int port)
-{
-    /* Create a new cluster object */
-    if (!cluster)
-      cluster = cass_cluster_new();
+DCDBConnection::DCDBConnection() {
+  if (!impl)
+    impl = new DCDBConnectionImpl();
+}
+
+DCDBConnection::DCDBConnection(std::string hostname, uint16_t port) {
+  if (!impl)
+    impl = new DCDBConnectionImpl();
 
-    if (!session)
-      session = cass_session_new();
+  impl->setHostname(hostname);
+  impl->setPort(port);
+}
 
-    /* Set hostname and port */
-    cass_cluster_set_contact_points(cluster, hostname.c_str());
-    cass_cluster_set_port(cluster, port);
+DCDBConnection::~DCDBConnection() {
+  if (impl)
+    delete impl;
+}
 
-    /* Force protcol version to 1 */
-    cass_cluster_set_protocol_version(cluster, 1);
 
-    /* Connect to the server */