private void DetectDownloadCountDecreases(DownloadData oldData, DownloadData newData, string id, ref int decreaseCount)
{
var oldHasId = oldData.TryGetValue(id, out var oldDownloads);
if (!oldHasId)
{
oldDownloads = new DownloadByVersionData();
}
var newHasId = newData.TryGetValue(id, out var newDownloads);
if (!newHasId)
{
newDownloads = new DownloadByVersionData();
}
var uniqueVersions = new HashSet <string>(
oldDownloads.Keys.Concat(newDownloads.Keys),
StringComparer.OrdinalIgnoreCase);
foreach (var version in uniqueVersions)
{
var oldHasVersion = oldDownloads.TryGetValue(version, out var oldCount);
var newHasVersion = newDownloads.TryGetValue(version, out var newCount);
if (newCount < oldCount)
{
decreaseCount++;
// Don't emit too many telemetry events. At a certain point the detail provided by additional events
// doesn't help investigation and can overwhelm Application Insights.
if (decreaseCount <= _options.Value.MaxDownloadCountDecreases)
{
_telemetryService.TrackDownloadCountDecrease(
id,
version,
oldHasId,
oldHasVersion,
oldCount,
newHasId,
newHasVersion,
newCount);
}
}
}
}