/**
* Retrieves the RRD stored data for the specified metric over the specified time range.
*
* @param rrdFilename the name of the RRD file containing the metric's data
* @param startTime start time, in seconds since Unix epoch, to fetch metric's data
* @param endTime end time, in seconds since Unix epoch, to fetch metric's data
* @return domain object containing the metric's sampled data, which consists of the timestamps
* and their associated values, and the total count of the sampled data
* @throws IOException
* @throws MetricsGraphException
*/
private MetricData getMetricData(String rrdFilename, long startTime, long endTime)
throws IOException, MetricsGraphException {
LOGGER.trace("ENTERING: getMetricData");
// Create RRD DB in read-only mode for the specified RRD file
RrdDb rrdDb = new RrdDb(rrdFilename, true);
// Extract the data source (should always only be one data source per RRD file - otherwise we
// have a problem)
if (rrdDb.getDsCount() != 1) {
throw new MetricsGraphException(
"Only one data source per RRD file is supported - RRD file "
+ rrdFilename
+ " has "
+ rrdDb.getDsCount()
+ " data sources.");
}
// The step (sample) interval that determines how often RRD collects the metric's data
long rrdStep = rrdDb.getRrdDef().getStep();
// Retrieve the RRD file's data source type (COUNTER or GAUGE) to determine how (later)
// to store the metric's data for presentation.
DsType dataSourceType = rrdDb.getDatasource(0).getType();
// Fetch the metric's data from the RRD file for the specified time range
FetchRequest fetchRequest = rrdDb.createFetchRequest(ConsolFun.TOTAL, startTime, endTime);
FetchData fetchData = fetchRequest.fetchData();
long[] timestamps = fetchData.getTimestamps();
double[] values = fetchData.getValues(0);
// Done retrieving data from the RRD database - close it, otherwise no one else will
// be able to access it later.
rrdDb.close();
// The lists of the metric's timestamps and their associated values that have non-"NaN" values
List<Long> validTimestamps = new ArrayList<Long>();
List<Double> validValues = new ArrayList<Double>();
long totalCount = 0;
MetricData metricData = new MetricData();
if (dataSourceType == DsType.COUNTER) {
// Counters are for constantly incrementing data, hence they can
// have a summation of their totals
metricData.setHasTotalCount(true);
for (int i = 0; i < timestamps.length; i++) {
// Filter out the RRD values that have not yet been sampled (they will
// have been set to NaN as a placeholder when the RRD file was created)
if (!Double.toString(values[i]).equals("NaN")) {
// RRD averages the collected samples over the step interval.
// To "undo" this averaging and get the actual count, need to
// multiply the sampled data value by the RRD step interval.
double nonAveragedValue = (double) (values[i] * rrdStep);
validTimestamps.add(timestamps[i]);
validValues.add(nonAveragedValue);
totalCount += (long) nonAveragedValue;
}
}
} else if (dataSourceType == DsType.GAUGE) {
// Gauges are for data that waxes and wanes, hence no total count
metricData.setHasTotalCount(false);
for (int i = 0; i < timestamps.length; i++) {
// Filter out the RRD values that have not yet been sampled (they will
// have been set to NaN as a placeholder when the RRD file was created)
if (!Double.toString(values[i]).equals("NaN")) {
validTimestamps.add(timestamps[i]);
validValues.add(values[i]);
}
}
}
metricData.setTimestamps(validTimestamps);
metricData.setValues(validValues);
metricData.setTotalCount(totalCount);
LOGGER.trace("EXITING: getMetricData");
return metricData;
}
