Open liuhj1018 opened 1 month ago
if (File.Exists(processFile))
{
string content = File.ReadAllText(processFile);
var newPack = JsonConvert.DeserializeObject
DownloadPackage
@liuhj1018 When you check the null condition for storage, don't update storage when it was used before. So, when I want to use the Downloader object again to download another URL, I get it wrong because I use an older storage stream and override the old data with new data.
Do you stop the Downloader process with the Stop()
method and then exit from your app or reboot it?
I ask this question because this issue didn't happen before this and when you call the stop, all processes have been done actually and disposed of this cycle. So, you can continue any time you want.
Do you stop the Downloader process with the method and then exit from your app or reboot it? I ask this question because this issue didn't happen before this and when you call the stop, all processes have been done actually and disposed of this cycle. So, you can continue any time you want.
Stop()
No, I don't call the stop method. I just simulate the program or the computer has benn suddenly shut down. This is not normal but happen. I will check null condition for storage, and the current and the next downloader.
I want to write the Package to the local file using "var packageJson = JsonConvert.SerializeObject(package);". But Where I put the sentence? OnDownloadProgressChanged or OnChunkDownloadProgressChanged method?
In the case of sudden shutdowns (like a power failure or unexpected program termination), you’ll want to back up the package
object, which contains the metadata necessary to resume the download. My Downloader library is designed to resume downloads by serializing the package
object as JSON and storing it in a file, database, or another persistent storage. This package can then be passed back to the Downloader to continue the download from where it left off.
You’re right to consider the performance impact of serializing the package on every OnProgress
event. While backing up on every event would ensure no data is lost, it could indeed be too resource-intensive. To address this, I recommend using a debounce algorithm to limit how often the serialization occurs. This will prevent redundant operations and reduce the performance overhead while ensuring that only the latest package is backed up.
Use OnDownloadProgressChanged
:
Handling Race Conditions:
Handling Sudden Shutdowns:
Here's a rough idea of how debouncing could be implemented:
private DateTime _lastSerializedTime = DateTime.MinValue;
private readonly TimeSpan _debounceInterval = TimeSpan.FromSeconds(5);
void OnDownloadProgressChanged(object sender, DownloadProgressChangedEventArgs e)
{
if (DateTime.Now - _lastSerializedTime > _debounceInterval)
{
var packageJson = JsonConvert.SerializeObject(package);
File.WriteAllText("packageBackup.json", packageJson);
_lastSerializedTime = DateTime.Now;
}
}
This way, you can ensure the package is backed up regularly without overwhelming the system.
I haven’t fully tested this particular scenario, but I believe this approach should work for your needs. Let me know if you need any more help with this!
two problems:
I don't Undrestand the right issue. According to the previews answer you must handle race conditions by debouncing and locking objects to prevent write conflict issues. please explain more about what happened.
1.packageBackup.json write conflict. I had used locking object method first, but its efficiency was low. So now I use File.WriteAllTextAsync method. 2.When I generate the local backup.json file, shutdown the program and restart, the file stream is initialized in the ConcurrentStream.cs (line 31) firstly, and then initialized in the DownloadPackage.cs (line 138) secondly. They are conflict. I add Storage nullvalue judgement to avoid initializing twice on the same file.
I download a large file. I put the downloadpackage json file to the disk. When I reboot the progress and resume from the json file, a error shows the datafile is in use. I find line 25 and line 87 same in the ConcurrentStream.cs and I modify the DownloadPackage.cs. The datafile can be downloaded correctly.
Is it a bug? or I use in a wrong way? Look forward for reply!