public static async Task <string> AcquireLeaseAsync(this CloudBlob blob, TimeSpan?leaseTime = null, CancellationToken cancellationToken = default(CancellationToken))
{
// From: https://msdn.microsoft.com/en-us/library/azure/ee691972.aspx
// The Lease Blob operation establishes and manages a lock on a blob for write and delete operations.
// The lock duration can be 15 to 60 seconds, or can be infinite.
if (leaseTime.HasValue && (leaseTime.Value <TimeSpan.FromSeconds(15) | leaseTime.Value> TimeSpan.FromSeconds(60)))
{
throw new ArgumentOutOfRangeException(nameof(leaseTime), string.Format("{0} must be between 15 and 60 seconds", nameof(leaseTime)));
}
var defaultLeaseTime = TimeSpan.FromSeconds(15);
var proposedLeaseId = (string)null; // Proposed lease id (leave it null for storage service to return you one).
var blobDoesNotExist = false;
var leaseId = (string)null;
leaseTime = leaseTime.HasValue ? leaseTime : defaultLeaseTime;
try
{
// Optimistically try to acquire the lease. The blob may not yet
// exist. If it doesn't we handle the 404, create it, and retry below
leaseId = await blob.AcquireLeaseAsync(leaseTime, proposedLeaseId, null, null, null, cancellationToken).ConfigureAwait(false);
}
catch (StorageException exception)
{
if (exception.RequestInformation != null)
{
if (exception.RequestInformation.HttpStatusCode == 404)
{
blobDoesNotExist = true;
}
else
{
throw;
}
}
else
{
throw;
}
}
if (blobDoesNotExist)
{
await blob.UploadTextAsync(string.Empty, null, cancellationToken);
leaseId = await blob.AcquireLeaseAsync(leaseTime, proposedLeaseId, null, null, null, cancellationToken).ConfigureAwait(false);
}
return(leaseId);
}
private static void DoLeaseOperation(CloudBlob blob, string leaseId, LeaseAction action)
{
switch (action)
{
case LeaseAction.Acquire:
blob.AcquireLeaseAsync(TimeSpan.FromSeconds(90), leaseId).Wait();
break;
case LeaseAction.Renew:
blob.RenewLeaseAsync(AccessCondition.GenerateLeaseCondition(leaseId)).Wait();
break;
case LeaseAction.Release:
blob.ReleaseLeaseAsync(AccessCondition.GenerateLeaseCondition(leaseId)).Wait();
break;
case LeaseAction.Break:
blob.BreakLeaseAsync(TimeSpan.FromSeconds(90)).Wait();
break;
case LeaseAction.Change:
blob.ChangeLeaseAsync(leaseId, AccessCondition.GenerateLeaseCondition(leaseId)).Wait();
break;
default:
throw new ArgumentOutOfRangeException(nameof(action), action, null);
}
}
public static async Task <string> TryAcquireLeaseAsync(this CloudBlob blob, TimeSpan?leaseTime = null, int maxLeaseAttempts = 1, CancellationToken cancellationToken = default(CancellationToken))
{
if (blob == null)
{
throw new ArgumentNullException(nameof(blob));
}
if (maxLeaseAttempts < 1 || maxLeaseAttempts > 10)
{
throw new ArgumentOutOfRangeException(string.Format("{0} must be between 1 and 10", nameof(maxLeaseAttempts)));
}
var leaseId = (string)null;
for (var attempts = 0; attempts < maxLeaseAttempts; attempts++)
{
try
{
leaseId = await blob.AcquireLeaseAsync(leaseTime, cancellationToken).ConfigureAwait(false);
if (!string.IsNullOrEmpty(leaseId))
{
break;
}
}
catch (StorageException e)
{
// If the status code is 409 (HttpStatusCode.Conflict), it means the resource is already leased
if (e.RequestInformation?.HttpStatusCode == 409)
{
if (attempts < maxLeaseAttempts - 1)
{
await Task.Delay(500).ConfigureAwait(false); // Make sure we don't retry too quickly
}
}
else
{
throw;
}
}
}
return(leaseId);
}
public static string AcquireLease(this CloudBlob blob, TimeSpan?leaseTime, string proposedLeaseId, AccessCondition accessCondition = null, BlobRequestOptions options = null, OperationContext operationContext = null)
{
return(blob.AcquireLeaseAsync(leaseTime, proposedLeaseId, accessCondition, options, operationContext).GetAwaiter().GetResult());
}