internal async Task <DatabaseMeasurementInfo> GetMetaInformationAsync(string db, string measurementName, TimeSpan?expiration)
{
var key = new DatabaseMeasurementInfoKey(db, measurementName);
DatabaseMeasurementInfo info;
lock (_seriesMetaCache)
{
_seriesMetaCache.TryGetValue(key, out info);
}
var now = DateTime.UtcNow;
if (info != null)
{
if (!expiration.HasValue) // info never expires
{
return(info);
}
if (now - info.Timestamp < expiration.Value) // has not expired
{
return(info);
}
}
// has expired or never existed, lets retrieve it
// get metadata information from the store
var tagsResult = await this.ShowTagKeysAsync(db, measurementName).ConfigureAwait(false);
var tags = tagsResult.Series.FirstOrDefault()?.Rows;
info = new DatabaseMeasurementInfo(now);
if (tags != null)
{
foreach (var row in tags)
{
info.Tags.Add(row.TagKey);
}
}
lock (_seriesMetaCache)
{
_seriesMetaCache[key] = info;
}
return(info);
}
internal async Task <DatabaseMeasurementInfo> GetMetaInformationAsync(string db, string measurementName, bool forceRefresh)
{
var key = new DatabaseMeasurementInfoKey(db, measurementName);
DatabaseMeasurementInfo info;
if (!forceRefresh)
{
lock ( _seriesMetaCache )
{
if (_seriesMetaCache.TryGetValue(key, out info))
{
return(info);
}
}
}
// get metadata information from the store
var fieldTask = ShowFieldKeysAsync(db, measurementName);
var tagTask = ShowTagKeysAsync(db, measurementName);
await Task.WhenAll(fieldTask, tagTask).ConfigureAwait(false);
var fields = fieldTask.Result.Series.FirstOrDefault()?.Rows;
var tags = tagTask.Result.Series.FirstOrDefault()?.Rows;
info = new DatabaseMeasurementInfo();
if (fields != null)
{
foreach (var row in fields)
{
info.Fields.Add(row.FieldKey);
}
}
if (tags != null)
{
foreach (var row in tags)
{
info.Tags.Add(row.TagKey);
}
}
lock ( _seriesMetaCache )
{
_seriesMetaCache[key] = info;
}
return(info);
}
