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Watcher.cs
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Watcher.cs
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using System.IO;
using System.Runtime.CompilerServices;
using System.Runtime.Serialization;
using System.Threading;
using System.Threading.Tasks;
using k8s.Models;
namespace k8s
{
/// <summary>Describes the type of a watch event.</summary>
public enum WatchEventType
{
/// <summary>Emitted when an object is created, modified to match a watch's filter, or when a watch is first opened.</summary>
[EnumMember(Value = "ADDED")]
Added,
/// <summary>Emitted when an object is modified.</summary>
[EnumMember(Value = "MODIFIED")]
Modified,
/// <summary>Emitted when an object is deleted or modified to no longer match a watch's filter.</summary>
[EnumMember(Value = "DELETED")]
Deleted,
/// <summary>Emitted when an error occurs while watching resources. Most commonly, the error is 410 Gone which indicates that
/// the watch resource version was outdated and events were probably lost. In that case, the watch should be restarted.
/// </summary>
[EnumMember(Value = "ERROR")]
Error,
/// <summary>Bookmarks may be emitted periodically to update the resource version. The object will
/// contain only the resource version.
/// </summary>
[EnumMember(Value = "BOOKMARK")]
Bookmark,
}
public class Watcher<T> : IDisposable
{
/// <summary>
/// indicate if the watch object is alive
/// </summary>
public bool Watching { get; private set; }
private readonly CancellationTokenSource _cts;
private readonly Func<Task<TextReader>> _streamReaderCreator;
private bool disposedValue;
[System.Diagnostics.CodeAnalysis.SuppressMessage("Design", "IDE0052:Remove unread private members", Justification = "Used in an async task loop")]
private readonly Task _watcherLoop;
/// <summary>
/// Initializes a new instance of the <see cref="Watcher{T}"/> class.
/// </summary>
/// <param name="streamReaderCreator">
/// A <see cref="StreamReader"/> from which to read the events.
/// </param>
/// <param name="onEvent">
/// The action to invoke when the server sends a new event.
/// </param>
/// <param name="onError">
/// The action to invoke when an error occurs.
/// </param>
/// <param name="onClosed">
/// The action to invoke when the server closes the connection.
/// </param>
public Watcher(Func<Task<StreamReader>> streamReaderCreator, Action<WatchEventType, T> onEvent,
Action<Exception> onError, Action onClosed = null)
: this(
async () => (TextReader)await streamReaderCreator().ConfigureAwait(false),
onEvent, onError, onClosed)
{
}
/// <summary>
/// Initializes a new instance of the <see cref="Watcher{T}"/> class.
/// </summary>
/// <param name="streamReaderCreator">
/// A <see cref="TextReader"/> from which to read the events.
/// </param>
/// <param name="onEvent">
/// The action to invoke when the server sends a new event.
/// </param>
/// <param name="onError">
/// The action to invoke when an error occurs.
/// </param>
/// <param name="onClosed">
/// The action to invoke when the server closes the connection.
/// </param>
public Watcher(Func<Task<TextReader>> streamReaderCreator, Action<WatchEventType, T> onEvent,
Action<Exception> onError, Action onClosed = null)
{
_streamReaderCreator = streamReaderCreator;
OnEvent += onEvent;
OnError += onError;
OnClosed += onClosed;
_cts = new CancellationTokenSource();
_watcherLoop = Task.Run(async () => await WatcherLoop(_cts.Token).ConfigureAwait(false));
}
/// <summary>
/// add/remove callbacks when any event raised from api server
/// </summary>
public event Action<WatchEventType, T> OnEvent;
/// <summary>
/// add/remove callbacks when any exception was caught during watching
/// </summary>
public event Action<Exception> OnError;
/// <summary>
/// The event which is raised when the server closes the connection.
/// </summary>
public event Action OnClosed;
public class WatchEvent
{
[JsonPropertyName("type")]
public WatchEventType Type { get; set; }
[JsonPropertyName("object")]
public T Object { get; set; }
}
private async Task WatcherLoop(CancellationToken cancellationToken)
{
try
{
Watching = true;
await foreach (var (t, evt) in CreateWatchEventEnumerator(_streamReaderCreator, OnError,
cancellationToken)
.ConfigureAwait(false)
)
{
OnEvent?.Invoke(t, evt);
}
}
catch (OperationCanceledException)
{
// ignore
}
catch (Exception e)
{
// error when transport error, IOException ect
OnError?.Invoke(e);
}
finally
{
Watching = false;
OnClosed?.Invoke();
}
}
internal static async IAsyncEnumerable<(WatchEventType, T)> CreateWatchEventEnumerator(
Func<Task<TextReader>> streamReaderCreator,
Action<Exception> onError = null,
[EnumeratorCancellation] CancellationToken cancellationToken = default)
{
Task<TR> AttachCancellationToken<TR>(Task<TR> task)
{
if (!task.IsCompleted)
{
// here to pass cancellationToken into task
return task.ContinueWith(t => t.GetAwaiter().GetResult(), cancellationToken);
}
return task;
}
using var streamReader = await AttachCancellationToken(streamReaderCreator()).ConfigureAwait(false);
for (; ; )
{
// ReadLineAsync will return null when we've reached the end of the stream.
var line = await AttachCancellationToken(streamReader.ReadLineAsync()).ConfigureAwait(false);
cancellationToken.ThrowIfCancellationRequested();
if (line == null)
{
yield break;
}
WatchEvent @event = null;
try
{
var genericEvent = KubernetesJson.Deserialize<Watcher<KubernetesObject>.WatchEvent>(line);
if (genericEvent.Object.Kind == "Status")
{
var statusEvent = KubernetesJson.Deserialize<Watcher<V1Status>.WatchEvent>(line);
var exception = new KubernetesException(statusEvent.Object);
onError?.Invoke(exception);
}
else
{
@event = KubernetesJson.Deserialize<WatchEvent>(line);
}
}
catch (Exception e)
{
onError?.Invoke(e);
}
if (@event != null)
{
yield return (@event.Type, @event.Object);
}
}
}
protected virtual void Dispose(bool disposing)
{
if (!disposedValue)
{
if (disposing)
{
_cts?.Cancel();
_cts?.Dispose();
}
disposedValue = true;
}
}
// // TODO: override finalizer only if 'Dispose(bool disposing)' has code to free unmanaged resources
// ~Watcher()
// {
// // Do not change this code. Put cleanup code in 'Dispose(bool disposing)' method
// Dispose(disposing: false);
// }
public void Dispose()
{
// Do not change this code. Put cleanup code in 'Dispose(bool disposing)' method
Dispose(true);
GC.SuppressFinalize(this);
}
}
}