public override async Task <TimeStampFeedEntries> GetTimeStampServers(CancellationToken cancellationToken = default)
{
// The following code makes sure that the list of servers is shown in a random order (not to prefer any specific server).
var originalList = await base.GetTimeStampServers(cancellationToken).ConfigureAwait(false);
if (originalList?.Servers?.Any() != true)
{
return(originalList);
}
Logger.Debug("Randomizing the list of timestamp servers...");
var randomList = new TimeStampFeedEntries
{
Servers = new List <TimeStampServerEntry>()
};
var rnd = new Random();
while (originalList.Servers.Any())
{
var randomElement = rnd.Next(0, originalList.Servers.Count);
randomList.Servers.Add(originalList.Servers[randomElement]);
originalList.Servers.RemoveAt(randomElement);
}
return(randomList);
}
public override async Task <TimeStampFeedEntries> GetTimeStampServers(CancellationToken cancellationToken = default)
{
Logger.Debug("Getting exclusive lock for cached read operation...");
var gotLock = this.syncObject.WaitOne(TimeSpan.FromSeconds(10));
try
{
if (!gotLock)
{
Logger.Debug("Could not get an exclusive lock in 10 seconds, aborting...");
return(new TimeStampFeedEntries());
}
if (this.cache?.Servers != null)
{
if (this.lastRead > DateTime.Now.Subtract(this.invalidateAfter))
{
Logger.Debug($"Returning the cached copy of servers (last modification {this.lastRead}) which is not older than {this.invalidateAfter} ago...");
return(this.cache);
}
Logger.Debug($"Invalidating the cached copy of servers (last modification {this.lastRead}) which was older than {this.invalidateAfter} ago...");
this.cache = null;
this.lastRead = DateTime.MinValue;
}
var file = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData, Environment.SpecialFolderOption.DoNotVerify), "msix-hero", "timestamps.json");
bool commit;
if (File.Exists(file))
{
var lastDate = File.GetLastWriteTimeUtc(file);
if (lastDate > DateTime.UtcNow.Subtract(this.invalidateAfter))
{
Logger.Debug($"Returning the local copy of servers from file {file} (last modification {lastDate}) which is not older than {this.invalidateAfter} ago...");
// the file is in accepted date range, so we can deserialize it and return the results
await using var fs = await this.OpenStream(cancellationToken).ConfigureAwait(false);
this.cache = await this.GetTimeStampServers(fs, cancellationToken).ConfigureAwait(false);
commit = false;
}
else
{
Logger.Debug($"Invalidating the cached copy of servers from file {file} (last modification {lastDate}) which is older than {this.invalidateAfter} ago...");
this.cache = await this.decoratedFeed.GetTimeStampServers(cancellationToken).ConfigureAwait(false);
this.lastRead = DateTime.UtcNow;
Logger.Info($"New last read date is {this.lastRead}.");
commit = true;
}
}
else
{
Logger.Debug("There is no cached copy available, getting the list from the actual provider...");
this.cache = await this.decoratedFeed.GetTimeStampServers(cancellationToken).ConfigureAwait(false);
this.lastRead = DateTime.UtcNow;
Logger.Info($"New last read date is {this.lastRead}.");
commit = true;
}
if (commit)
{
var fileInfo = new FileInfo(file);
if (fileInfo.Exists)
{
Logger.Info($"Deleting existing cached copy {fileInfo.FullName}...");
fileInfo.Delete();
}
else if (fileInfo.Directory?.Exists == false)
{
Logger.Info($"Creating directory {fileInfo.Directory.FullName}...");
fileInfo.Directory.Create();
}
Logger.Debug($"Serializing cached entries into JSON format...");
var jsonString = JsonConvert.SerializeObject(this.cache, Formatting.Indented);
Logger.Debug($"Writing cached entries in JSON format into {fileInfo.FullName}...");
await File.WriteAllTextAsync(fileInfo.FullName, jsonString, cancellationToken).ConfigureAwait(false);
}
return(this.cache);
}
finally
{
if (gotLock)
{
Logger.Debug("Returning from exclusive lock...");
this.syncObject.Set();
}
}
}
