/**
     * getNoSQLResource() -- private static method
     *
     * this method initializes the nosql resource by attempting to connect to the nosql service.  if the connection
     * attempt succeeds, then mark the resource as available.  Otherwise, post an error-fatal and explicitly mark
     * the service as not-available and return.
     *
     * NOTE:
     * -----
     * This resource allocation exists outside of the resource manager because the resource manager instantiates
     * this class in it's constructor.  Were you to request a resource from the resource manager, you'd end-up in
     * a circular reference and if the whole thing does not come to an immediate shuddering stop, then it would
     * certainly blow-up the first time you attempt to log an error.  So, tl;dr:  do not attempt to 'fix' this as
     * it's not broken.
     *
     * @author  mike@givingassistant.org
     * @version 1.0
     *
     * @return Aws\DynamoDb\DynamoDbClient|null
     *
     * HISTORY:
     * ========
     * 06-09-17     mks     original coding
     *
     */
    private function getNoSQLResource():Aws\DynamoDb\DynamoDbClient
    {
        global $eos;
        $options = null;
        date_default_timezone_set(TIME_TIMEZONE);

        if (empty($this->config)) {
            echo getDateTime() . CON_ERROR . $this->res . ERROR_CONFIG_RESOURCE_404 . CONFIG_DATABASE_DDB . $eos;
            return(null);
        }

        $noSQLConfig = $this->config[CONFIG_DATABASE_DDB_APPSERVER];
        $credentials = [
            STRING_KEY => $noSQLConfig[CONFIG_DATABASE_DDB_APPSERVER_KEY_ID],
            STRING_SECRET => $noSQLConfig[CONFIG_DATABASE_DDB_APPSERVER_ACCESS_KEY]
        ];

        /*
         * Requests to DynamoDB are made over HTTP(S), and this does not require that you establish an upfront
         * connection. When you create the client object, you are not making a connection to DynamoDB, you are just
         * configuring an HTTP client that will make requests to DynamoDB.
         */

        $awsConfig = new Aws\Sdk([
            STRING_ENDPOINT => $noSQLConfig[CONFIG_DATABASE_DDB_APPSERVER_DSN] . ':' . $noSQLConfig[CONFIG_DATABASE_DDB_APPSERVER_PORT],
            STRING_REGION => $noSQLConfig[CONFIG_DATABASE_DDB_APPSERVER_REGION],
            STRING_VERSION => $noSQLConfig[CONFIG_DATABASE_DDB_APPSERVER_VERSION],
            STRING_CREDS => $credentials
        ]);
        return $awsConfig->createDynamoDb();
    }


    /**
     * getLog() - public method
     *
     * getLog is the method that is used to fetch log (or Metrics) records from the mongo collection.
     *
     * because ddb limits queries to 1MB returns, and the paint is still wet on this schema, for now I'm
     * going to limit queries for log-file fetching to just the last N records created within the last hour and
     * we'll just grab up to the limit of the records returned - which should still be a significant number of
     * records...
     *
     * This method reads the last X records created in the last hour (since this method is mainly used for
     * providing HTML output to the log-reader) and wraps the data in HTML table rows intended for the logDump
     * utility.
     *
     * todo -- pagination support?  Query by error-code?  Query by eventID?  Query by class?
     *
     * @author  mshallop@pathway.com
     * @version 1.0
     *
     * @param  string $_what    defaults to the log template -- should be over-ridden for metrics template
     * @return null|string
     * @throws Exception
     *
     * HISTORY:
     * ========
     * 06-07-17     mks     original coding
     * 06-14-17     mks     refactored for ddb
     *
     */
    public function getLog(string $_what = TEMPLATE_CLASS_LOGS):string
    {
        $result = null;
        $returnData = null;
        $marshaler = new Marshaler();           // black-box son converter
        $lastHour = time() - NUMBER_ONE_HOUR_SEC;
        if ($_what != TEMPLATE_CLASS_LOGS and $_what != TEMPLATE_CLASS_METRICS) $_what = TEMPLATE_CLASS_LOGS;

        $eav = $marshaler->marshalJson('{":ts" :' . $lastHour . '}');

        $params = [
            DDB_STRING_TABLE_NAME => $this->collectionName,
            DDB_STRING_KEY_COND_EXPR => LOG_CREATED . ' > :ts',
            DDB_STRING_EXPR_ATTR_VALS => $eav
        ];

        try {
            $result = $this->connection->query($params);
        } catch (DynamoDbException $e) {
            $this->errStack[] = __FILE__ . ':' . __LINE__ . ':' . __METHOD__ . ':' . $this->class . ':' .
                ERROR_FATAL . ' caught cursor exception: ' . $e->getMessage();
            self::throwFatal();
        }
        if (!is_null($result)) {
            foreach ($result[DDB_STRING_ITEMS] as $row) {
                $returnData .= '<div class="rowMeta">';  // note: css is defined in the utilities directory
                $returnData .= '(' . $row[(DB_PKEY . $this->ext)]  . ') - ';
//                $returnData .= date(TIME_DATE_FORMAT, $row[(META_SESSION_DATE . self::$ext)]->sec) . ' - ';

                // add error label as a span: warn/error/fatal...
                $returnData .= self::getErrorLabel($row[(LOG_LEVEL . $this->ext)]);

                $returnData .= ' ' . $row[(ERROR_FILE . $this->ext)] . '(' . $row[(ERROR_LINE . $this->ext)] . ')';
                $cd = '';
                if (!empty($row[(ERROR_CLASS . $this->ext)])) $cd = ' class[' . $row[(ERROR_CLASS . $this->ext)] . ']';
                if (!empty($row[(ERROR_METHOD . $this->ext)])) $cd .= '.method(' . $row[(ERROR_METHOD . $this->ext)] . ')</div>';
                $returnData .= $cd;
                /*
                                if ($row[(ERROR_TYPE . self::$ext)] == ERROR_TRACE) {
                                    $returnData .= '</div>';
                                }
                */
                $returnData .= '<div class="rowData">' . htmlentities($row[(ERROR_MESSAGE . $this->ext)]);
                if ($_what == TEMPLATE_CLASS_METRICS) {
                    $returnData .= ' - ' . $row[(DB_TIMER . $this->ext)] . ' or ';
                    $returnData .= ($row[(DB_TIMER . $this->ext)] * NUMBER_MS_PER_SEC) . 'ms';
                }
                $returnData .= '</div>';
                $returnData .= '<div class="rowHist">';
                foreach($row[(DB_HISTORY . $this->ext)] as $histRec) {
                    $returnData .= date('Y-M-d h:i:s', $histRec[META_SESSION_DATE]->sec);// . ' (';
                    if (!is_null($row[(LOG_EVENT_GUID . $this->ext)]))
                        $returnData .= ', Event ID: ' . $row[(LOG_EVENT_GUID . $this->ext)];
//                    $returnData .= $histRec[META_SESSION_EVENT] . ') from (';
//                    $returnData .= $histRec[META_SESSION_IP] . '): ';
//                    $returnData .= ((isset($histRec[META_SESSION_ID])) ? $histRec[META_SESSION_ID] : $histRec[META_CLIENT]) . '<br />';
                }
                $returnData .= '</div><br />';
            }
        }
        return ($returnData);
    }