private async Task <(DatabaseUsage DbUsage, File Cached)> GetFromCache(CancellationToken cancel)
{
File cached = null;
DatabaseUsage databaseUsage = null;
try
{
using (new SystemAccount())
{
cached = await Node.LoadAsync <File>(DatabaseUsageCachePath, cancel)
.ConfigureAwait(false);
}
if (cached != null)
{
if (DateTime.UtcNow - cached.ModificationDate <= DatabaseUsageCacheTime)
{
databaseUsage = (DatabaseUsage)cached.GetCachedData(CacheKey);
if (databaseUsage == null)
{
var src = RepositoryTools.GetStreamString(cached.Binary.GetStream());
databaseUsage = JsonConvert.DeserializeObject <DatabaseUsage>(src);
cached.SetCachedData(CacheKey, databaseUsage);
}
}
}
}
catch (Exception e)
{
_logger.LogWarning("An error occurred during loading DatabaseUsage.cache: " + e);
// do nothing
}
return(databaseUsage, cached);
}
private async STT.Task PutToCacheAsync(DatabaseUsage databaseUsage, File cached, CancellationToken cancel)
{
var resultBuilder = new StringBuilder();
using (var writer = new StringWriter(resultBuilder))
JsonSerializer.Create(SerializerSettings).Serialize(writer, databaseUsage);
using (new SystemAccount())
{
cached ??= await CreateCacheFileAsync(cancel);
if (cached == null)
{
return;
}
var iteration = 0;
try
{
var serialized = resultBuilder.ToString();
var cachedStream = !cached.IsNew ? cached.Binary?.GetStream() : null;
var cachedData = cachedStream != null?RepositoryTools.GetStreamString(cachedStream) : string.Empty;
// save the content only if there was a change
if (string.Equals(serialized, cachedData))
{
return;
}
Retrier.Retry(5, 500, typeof(NodeIsOutOfDateException), () =>
{
iteration++;
// reload to have a fresh instance
if (!cached.IsNew && iteration > 1)
{
cached = Node.Load <File>(cached.Id);
}
cached.SetCachedData(CacheKey, databaseUsage);
cached.Binary.SetStream(RepositoryTools.GetStreamFromString(serialized));
cached.Save(SavingMode.KeepVersion);
_logger.LogTrace($"DatabaseUsage.cache has been saved. Iteration: {iteration}");
});
}
catch (Exception e)
{
_logger.LogWarning(e, $"An error occurred during saving DatabaseUsage.cache in iteration {iteration}.");
// do nothing
}
}
}
protected static string GetBinaryText(File file)
{
if (file == null)
{
return(string.Empty);
}
using (var stream = file.Binary.GetStream())
{
return(RepositoryTools.GetStreamString(stream) ?? string.Empty);
}
}