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Watcher

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This commit is contained in:
Jöran Malek 2023-11-26 01:50:32 +01:00
parent 7131259eba
commit 4508324ff5
1 changed files with 50 additions and 21 deletions
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69
src/pdns-dhcp/Kea/KeaLeaseWatcher.cs
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@ -2,12 +2,23 @@ using System.Threading.Channels;
using Microsoft.Extensions.Hosting;
using nietras.SeparatedValues;
using pdns_dhcp.Options;
using Stl.Async;
namespace pdns_dhcp.Kea;
public abstract class KeaDhcpLeaseWatcher : IHostedService
{
private static readonly FileStreamOptions _leaseFileStreamOptions = new()
{
Access = FileAccess.Read,
Mode = FileMode.Open,
Options = FileOptions.SequentialScan,
Share = (FileShare)7,
};
private readonly FileSystemWatcher _fsw;
private readonly string _leaseFile;
private Channel<FileSystemEventArgs>? _eventChannel;
@ -69,30 +80,38 @@ public abstract class KeaDhcpLeaseWatcher : IHostedService
private async Task Reading(CancellationToken stoppingToken)
{
SemaphoreSlim readerLock = new(1, 1);
while (!stoppingToken.IsCancellationRequested)
{
using CancellationTokenSource loopCts = CancellationTokenSource.CreateLinkedTokenSource(stoppingToken);
var loopToken = loopCts.Token;
_eventChannel = Channel.CreateUnbounded<FileSystemEventArgs>();
_fsw.EnableRaisingEvents = true;
ValueTask reader = default;
Task reader = FileReader(loopToken);
try
{
await foreach (var @event in _eventChannel.Reader.ReadAllAsync(loopCts.Token))
await foreach (var @event in _eventChannel.Reader.ReadAllAsync(loopToken))
{
// Guard for Deleted-events and moved-away events,
// both have to stop this reader immediately.
// Just wait for the file being created/moved to _leaseFile.
// Described in [The LFC Process](https://kea.readthedocs.io/en/latest/arm/lfc.html#kea-lfc)
switch (@event)
{
case { ChangeType: WatcherChangeTypes.Created }:
case RenamedEventArgs { ChangeType: WatcherChangeTypes.Renamed } renamed when renamed.Name == _leaseFile:
reader = FileReader(loopCts.Token);
break;
case { ChangeType: WatcherChangeTypes.Deleted }:
case RenamedEventArgs { ChangeType: WatcherChangeTypes.Renamed } renamed when renamed.OldName == _leaseFile:
case RenamedEventArgs renamed when renamed.OldName == _leaseFile:
loopCts.Cancel();
break;
continue;
}
if (reader is not { IsCompleted: false })
{
reader = FileReader(loopToken);
}
if (@event.ChangeType == WatcherChangeTypes.Changed)
{
case { ChangeType: WatcherChangeTypes.Changed }:
break;
}
}
}
@ -100,6 +119,8 @@ public abstract class KeaDhcpLeaseWatcher : IHostedService
finally
{
_eventChannel.Writer.TryComplete();
if (reader is { IsCompleted: false })
{
try
{
await reader.ConfigureAwait(continueOnCapturedContext: false);
@ -107,13 +128,18 @@ public abstract class KeaDhcpLeaseWatcher : IHostedService
catch { }
}
}
ValueTask FileReader(CancellationToken stoppingToken)
{
return ValueTask.CompletedTask;
}
}
private async Task FileReader(CancellationToken stoppingToken)
{
try
{
using var fileStream = new FileStream(Options.Leases, _leaseFileStreamOptions);
}
catch { }
}
private void OnLeaseChanged(object sender, FileSystemEventArgs e)
{
var writer = _eventChannel?.Writer;
@ -122,13 +148,16 @@ public abstract class KeaDhcpLeaseWatcher : IHostedService
return;
}
var write = writer.WriteAsync(e);
if (write.IsCompleted)
#pragma warning disable CA2012 // Task is awaited immediately.
if (writer.WriteAsync(e) is { IsCompleted: false } task)
{
return;
try
{
task.GetAwaiter().GetResult();
}
write.GetAwaiter().GetResult();
catch { }
}
#pragma warning restore
}
private void OnLeaseError(object sender, ErrorEventArgs e)