sensordatastore.cpp 7.69 KB
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/*
 * sensordatastore.cpp
 *
 *  Created on: Jul 24, 2013
 *      Author: Axel Auweter
 */

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/**
 * @mainpage
 * The DCDBLib library is a dynamic runtime library providing
 * functions to initialize and access the DCDB data store. It
 * is being used by the CollectAgent to handle insertion of
 * data and can be used by tools responsible for data analysis.
 *
 * Its main class is the SensorDataStore class which provides
 * functions to connect to the data store, initialize an empty
 * data base and to (TODO) retrieve data.
 *
 * For its internal handling, SensorDataStore relies on the
 * SensorDataStoreImpl class (which hides all private member
 * functions belonging to the SensorDataStore class from the
 * header that is used by programmers who link against this
 * library). Raw database functionality is abstracted into the
 * CassandraBackend class (to easy switching to other
 * key-value style databases in the future).
 *
 * To use the library in your client application, simnply
 * include the sensordatastore.h header file and initialize
 * an object of the SensorDataStore class.
 */

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#include "sensordatastore_internal.h"

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/**
 * @details
 * This function serializes a SensorId object into a
 * big-endian 128-bit character array represented as
 * std::string.
 */
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string SensorDataStoreImpl::sidConvert(SensorId *sid)
{
    uint64_t ll[2];
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    ll[0] = Endian::hostToBE(sid->raw[0]);
    ll[1] = Endian::hostToBE(sid->raw[1]);
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    return string((char*)ll, 16);
}

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/**
 * @details
 * The conversion of a MQTT message topic to a SensorId
 * object is performed by byte-wise scanning of the string,
 * and skipping of all characters except for those in the
 * range [0-9,a-f,A-F]. Each character is then turned from
 * hex string into its binary representation an OR'ed into
 * the 128-bit raw fields of the SensorId object.
 *
 * Applications should not call this function directly, but
 * use the topicToSid function provided by the
 * SensorDataStore class.
 */
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bool SensorDataStoreImpl::topicToSid(SensorId* sid, string topic)
{
    uint64_t pos = 0;
    const char* buf = topic.c_str();
    sid->raw[0] = 0;
    sid->raw[1] = 0;
    while (*buf) {
        if (*buf >= '0' && *buf <= '9') {
            sid->raw[pos / 64] |= (((uint64_t)(*buf - '0')) << (60-(pos%64)));
            pos += 4;
        }
        else if (*buf >= 'A' && *buf <= 'F') {
            sid->raw[pos / 64] |= (((uint64_t)(*buf - 'A' + 0xa)) << (60-(pos%64)));
            pos += 4;
        }
        else if (*buf >= 'a' && *buf <= 'f') {
            sid->raw[pos / 64] |= (((uint64_t)(*buf - 'a' + 0xa)) << (60-(pos%64)));
            pos += 4;
        }
        buf++;
    }
    return pos == 128;
}

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/**
 * @details
 * Initialization of the SensorDataStore happens in three
 * steps:
 *  - Establish Connection
 *  - Check if all keyspaces are present and create them if not
 *  - Check if all column families are present and create them if not
 *
 *  Applications should not call this function directly, but
 *  use the init function provideed by the SensorDataStore class.
 */
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void SensorDataStoreImpl::init(string hostname, int port) {

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    /*
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     * Open the connection to the Cassandra database and
     * create the necessary keyspace and column family.
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     */
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    try {
        csBackend->connect(hostname, port);

        if (!csBackend->existsKeyspace(KEYSPACE_NAME)) {
            cout << "Creating Keyspace " << KEYSPACE_NAME << "...\n";
            csBackend->createKeyspace(KEYSPACE_NAME, 1);
        }

        csBackend->selectKeyspace(KEYSPACE_NAME);

        if (!(csBackend->currentKeySpace.name.compare(KEYSPACE_NAME) == 0)) {
            cout << "Cannot select keyspace " << KEYSPACE_NAME << "\n";
            exit(EXIT_FAILURE);
        }

        if (!csBackend->existsColumnFamily(CF_SENSORDATA)) {
            cout << "Creating Column Familiy " CF_SENSORDATA "...\n";
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            csBackend->createColumnFamily(CF_SENSORDATA,
                "sid blob, ts bigint, value bigint",
                "sid, ts",
                "COMPACT STORAGE");
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        }
    }
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    catch(const TTransportException& te){
        cout << "TP Exception: " << te.what() << "[" << te.getType() << "]\n";
        exit(EXIT_FAILURE);
    }
    catch(const InvalidRequestException& ire){
        cout << "IRE Exception: " << ire.what() << "[" << ire.why << "]\n";
        exit(EXIT_FAILURE);
    }
    catch(const NotFoundException& nfe){
        cout << "NF Exception: " <<  nfe.what() << "\n";
        exit(EXIT_FAILURE);
    }
}

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/**
 * @details
 * To insert a sensor reading, the Rsvd field of the SensorId must
 * be filled with a time component that ensures that the maximum
 * number of 2^32 columns per key is not exceeded while still
 * allowing relatively easy retrieval of data.
 *
 * We achieve this by using a "week-stamp" (i.e. number of weeks
 * since Unix epoch) within the Rsvd field of the SensorId before
 * calling the Cassandra Backend to do the raw insert.
 *
 * Applications should not call this function directly, but
 * use the insert function provided by the SensorDataStore class.
 */
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void SensorDataStoreImpl::insert(SensorId* sid, uint64_t ts, uint64_t value)
{
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  /* Calculate and insert week number */
  uint16_t week = ts / 604800000000;
  sid->dsid.rsvd = week;

  /* Insert into Cassandra */
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  csBackend->insert(CF_SENSORDATA, sidConvert(sid), ts, value);
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}

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/**
 * @details
 * This constructor only sets the internal csBackend variable to
 * the externally provided CassandraBackend object.
 */
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SensorDataStoreImpl::SensorDataStoreImpl(CassandraBackend *csb)
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{
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  csBackend = csb;
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}

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/**
 * @details
 * Due to the simplicity of the class, the destructor is left empty.
 */
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SensorDataStoreImpl::~SensorDataStoreImpl()
{
}

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/**
 * @details
 * The main task of this function is to ensure that the
 * SensorDataStore object owns an instance of SensorDataStoreImpl.
 * Once this is ensured, the actual initialization work is
 * performed by the init function of SensorDataStoreImpl.
 */
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void SensorDataStore::init(string hostname, int port)
{
    /* Allocate new SensorDataStoreImpl Object if necessary */
    if (!impl) {
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        impl = new SensorDataStoreImpl(csBackend);
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    }
    
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    /* Call the Impl class init function */
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    impl->init(hostname, port);
}

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/**
 * @details
 * Instead of doing the actual work, this function simply
 * forwards to the insert function of the SensorDataStoreImpl
 * class.
 */
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bool SensorDataStore::topicToSid(SensorId* sid, std::string topic)
{
    return impl->topicToSid(sid, topic);
}

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/**
 * @details
 * Instead of doing the actual work, this function simply
 * forwards to the insert function of the SensorDataStoreImpl
 * class.
 */
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void SensorDataStore::insert(SensorId* sid, uint64_t ts, uint64_t value)
{
    impl->insert(sid, ts, value);
}

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/**
 * @details
 * This constructor for SensorDataStore acts similarly to the
 * standard constructor by calling the standard constructor
 * with "localhost" as the hostname and 9160 as the port number.
 */
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SensorDataStore::SensorDataStore()
{
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    csBackend = new CassandraBackend();
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    impl = nullptr;
    init("localhost", 9160);
}

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/**
 * @details
 * This constructor for SensorDataStore objects initializes
 * the object and connects to the database at the given
 * hostname on the given port.
 *
 * For this, the constructor allocates a CassandraBackend
 * object that is then used by SensorDataStoreImpl for doing
 * the raw database accesses.
 */
SensorDataStore::SensorDataStore(std::string hostname, int port)
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{
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    csBackend = new CassandraBackend();
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    impl = nullptr;
    init(hostname, port);
}

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/**
 * @details
 * The SensorDataStore desctructor deallocates the
 * SensorDataStoreImpl and CassandraBackend objects.
 */
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SensorDataStore::~SensorDataStore()
{
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  /* Clean up... */
  if (impl)
    delete impl;
  if (csBackend)
    delete csBackend;

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}