sensordatastore.cpp 5.61 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).
 *
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 * To use the library in your client application, simply
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 * include the sensordatastore.h header file and initialize
 * an object of the SensorDataStore class.
 */

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#include <string>
#include <iostream>
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#include <cstdint>
#include <cinttypes>
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#include "cassandra.h"
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#include "sensordatastore.h"
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#include "sensordatastore_internal.h"
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#include "connection.h"
#include "dcdbglobals.h"

#include "dcdbendian.h"
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/**
 * @details
 * Since we want high-performance inserts, we prepare the
 * insert CQL query in advance and only bind it on the actual
 * insert.
 */
void SensorDataStoreImpl::prepareInsert(uint64_t ttl)
{
  CassError rc = CASS_OK;
  CassFuture* future = NULL;
  const char* query;

  /*
   * Free the old prepared if necessary.
   */
  if (preparedInsert) {
      cass_prepared_free(preparedInsert);
  }

  char *queryBuf = NULL;
  if (ttl == 0) {
      query = "INSERT INTO dcdb.sensordata (sid, ts, value) VALUES (?, ?, ?);";
  }
  else {
      queryBuf = (char*)malloc(256);
      snprintf(queryBuf, 256, "INSERT INTO dcdb.sensordata (sid, ts, value) VALUES (?, ?, ?) USING TTL %" PRIu64 " ;", ttl);
      query = queryBuf;
  }

  future = cass_session_prepare(session, query);
  cass_future_wait(future);

  rc = cass_future_error_code(future);
  if (rc != CASS_OK) {
      connection->printError(future);
  } else {
      preparedInsert = cass_future_get_prepared(future);
  }

  cass_future_free(future);
  if (queryBuf) {
      free(queryBuf);
  }
}

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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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#if 0
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  std::cout << "Inserting@SensorDataStoreImpl (" << sid->raw[0] << " " << sid->raw[1] << ", " << ts << ", " << value << ")" << std::endl;
#endif

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  /* Calculate and insert week number */
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  uint16_t week = ts / 604800000000000;
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  sid->setRsvd(week);
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  /* Insert into Cassandra */
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  std::string key = sid->serialize();
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  CassError rc = CASS_OK;
  CassStatement* statement = NULL;
  CassFuture *future = NULL;

  statement = cass_prepared_bind(preparedInsert);

  cass_statement_bind_bytes_by_name(statement, "sid", (cass_byte_t*)(key.c_str()), 16);
  cass_statement_bind_int64_by_name(statement, "ts", ts);
  cass_statement_bind_int64_by_name(statement, "value", value);

  future = cass_session_execute(session, statement);

  cass_future_wait(future);

  rc = cass_future_error_code(future);
  if (rc != CASS_OK) {
      connection->printError(future);
  }

  cass_future_free(future);
  cass_statement_free(statement);
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}

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/**
 * @details
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 * This function updates the prepared statement for inserts
 * with the new TTL value.
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 */
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void SensorDataStoreImpl::setTTL(uint64_t ttl)
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{
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  prepareInsert(ttl);
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}

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/**
 * @details
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 * This constructor sets the internal connection variable to
 * the externally provided DCDBConnection object and also
 * retrieves the CassSession pointer of the connection.
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 */
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SensorDataStoreImpl::SensorDataStoreImpl(DCDBConnection* conn)
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{
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  connection = conn;
  session = connection->getSessionHandle();
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  preparedInsert = nullptr;
  prepareInsert(0);
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}

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/**
 * @details
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 * Due to the simplicity of the class, the destructor is left empty.
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 */
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SensorDataStoreImpl::~SensorDataStoreImpl()
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{
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  connection = nullptr;
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  session = nullptr;
  if (preparedInsert) {
      cass_prepared_free(preparedInsert);
  }
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}

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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
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 * Instead of doing the actual work, this function simply
 * forwards to the insert function of the SensorDataStoreImpl
 * class.
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 */
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void SensorDataStore::setTTL(uint64_t ttl)
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{
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    impl->setTTL(ttl);
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}

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/**
 * @details
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 * This constructor allocates the implementation class which
 * holds the actual implementation of the class functionality.
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 */
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SensorDataStore::SensorDataStore(DCDBConnection* conn)
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{
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    impl = new SensorDataStoreImpl(conn);
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}

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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;
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}