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using Microsoft.Extensions.Caching.Memory;
namespace Nop.Core.Caching;
/// <summary>
/// A distributed cache manager that locks the acquisition task
/// </summary>
public partial class MemoryCacheLocker : ILocker
{
#region Fields
protected readonly IMemoryCache _memoryCache;
#endregion
#region Ctor
public MemoryCacheLocker(IMemoryCache memoryCache)
{
_memoryCache = memoryCache;
}
#endregion
#region Utilities
/// <summary>
/// Run action
/// </summary>
/// <param name="key">The key of the background task</param>
/// <param name="expirationTime">The time after which the lock will automatically be expired</param>
/// <param name="action">The action to perform</param>
/// <param name="cancellationTokenSource">A CancellationTokenSource for manually canceling the task</param>
/// <returns></returns>
protected virtual async Task<bool> RunAsync(string key, TimeSpan? expirationTime, Func<CancellationToken, Task> action, CancellationTokenSource cancellationTokenSource = default)
{
var started = false;
try
{
var tokenSource = _memoryCache.GetOrCreate(key, entry => new Lazy<CancellationTokenSource>(() =>
{
entry.AbsoluteExpirationRelativeToNow = expirationTime;
entry.SetPriority(CacheItemPriority.NeverRemove);
started = true;
return cancellationTokenSource ?? new CancellationTokenSource();
}, true))?.Value;
if (tokenSource != null && started)
await action(tokenSource.Token);
}
catch (OperationCanceledException) { }
finally
{
if (started)
_memoryCache.Remove(key);
}
return started;
}
#endregion
#region Methods
/// <summary>
/// Performs some asynchronous task with exclusive lock
/// </summary>
/// <param name="resource">The key we are locking on</param>
/// <param name="expirationTime">The time after which the lock will automatically be expired</param>
/// <param name="action">Asynchronous task to be performed with locking</param>
/// <returns>A task that resolves true if lock was acquired and action was performed; otherwise false</returns>
public virtual async Task<bool> PerformActionWithLockAsync(string resource, TimeSpan expirationTime, Func<Task> action)
{
return await RunAsync(resource, expirationTime, _ => action());
}
/// <summary>
/// Starts a background task with "heartbeat": a status flag that will be periodically updated to signal to
/// others that the task is running and stop them from starting the same task.
/// </summary>
/// <param name="key">The key of the background task</param>
/// <param name="expirationTime">The time after which the heartbeat key will automatically be expired. Should be longer than <paramref name="heartbeatInterval"/></param>
/// <param name="heartbeatInterval">The interval at which to update the heartbeat, if required by the implementation</param>
/// <param name="action">Asynchronous background task to be performed</param>
/// <param name="cancellationTokenSource">A CancellationTokenSource for manually canceling the task</param>
/// <returns>A task that resolves true if lock was acquired and action was performed; otherwise false</returns>
public virtual async Task RunWithHeartbeatAsync(string key, TimeSpan expirationTime, TimeSpan heartbeatInterval, Func<CancellationToken, Task> action, CancellationTokenSource cancellationTokenSource = default)
{
// We ignore expirationTime and heartbeatInterval here, as the cache is not shared with other instances,
// and will be cleared on system failure anyway. The task is guaranteed to still be running as long as it is in the cache.
await RunAsync(key, null, action, cancellationTokenSource);
}
/// <summary>
/// Tries to cancel a background task by flagging it for cancellation on the next heartbeat.
/// </summary>
/// <param name="key">The task's key</param>
/// <param name="expirationTime">The time after which the task will be considered stopped due to system shutdown or other causes,
/// even if not explicitly canceled.</param>
/// <returns>A task that represents requesting cancellation of the task. Note that the completion of this task does not
/// necessarily imply that the task has been canceled, only that cancellation has been requested.</returns>
public virtual Task CancelTaskAsync(string key, TimeSpan expirationTime)
{
if (_memoryCache.TryGetValue(key, out Lazy<CancellationTokenSource> tokenSource))
tokenSource.Value.Cancel();
return Task.CompletedTask;
}
/// <summary>
/// Check if a background task is running.
/// </summary>
/// <param name="key">The task's key</param>
/// <returns>A task that resolves to true if the background task is running; otherwise false</returns>
public virtual Task<bool> IsTaskRunningAsync(string key)
{
return Task.FromResult(_memoryCache.TryGetValue(key, out _));
}
#endregion
}