Dfyjkt

Noticed the following behavior in my team’s application:

Multiple threads trying to acquire the lease on the same blob using the line below:

await blob.AcquireLeaseAsync(TimeSpan.FromSeconds(lockTime), null, null, new BlobRequestOptions() RetryPolicy = RetryPolicy , null);

Multiple threads got a lease successfully, each got a different lease, around the same time.
This is because AcquireLeaseAsync is NOT thread-safe right?
I thought lease is a lock, so it can only be granted to one thread at a time?

We tried to add an access condition of lease ID being null, which seems to be helpful.

await blob.AcquireLeaseAsync(TimeSpan.FromSeconds(lockTime), null, new AccessCondition LeaseId = null, new BlobRequestOptions() RetryPolicy = RetryPolicy , null);

But not sure if it’s fool-proof, i.e is there a chance multiple threads can pass this access condition when trying to acquire lease on the blob?

Below is the code that I use to generate this issue:

class Program

 static void Main(string args)
 
 Console.WriteLine("started");
 var storageConnStr = "";
 var client = CloudStorageAccount.Parse(storageConnStr).CreateCloudBlobClient();
 var container = client.GetContainerReference("test");
 var blob = container.GetBlobReference("Program.cs");
 List<Task> list = new List<Task>();

 for (int i = 0; i < 100; i++)
 
 list.Add(Task.Run(() => AcquireLease(blob)));
 
 Task.WhenAll(list).Wait();

 
 static void AcquireLease(CloudBlob blob)
 
 try
 
 var id = blob.AcquireLeaseAsync(TimeSpan.FromSeconds(30), null, null, null, null).Result;
 Console.WriteLine($"Successfully acquired lease on thread Thread.CurrentThread.ManagedThreadId, lease id id, time is DateTime.UtcNow");
 
 catch (Exception)
 
 Console.WriteLine($"Got exception at Thread.CurrentThread.ManagedThreadId");
 
 

Sample output:

Successfully acquired lease on thread 86, lease id
dfbd393e-46e2-49dc-98f4-853356fbc255, time is 11/10/2018 2:16:57 AM

Successfully acquired lease on thread 22, lease id
f81b3dbf-68f6-401d-b82e-a1c19fb3527c, time is 11/10/2018 2:16:57 AM

Successfully acquired lease on thread 54, lease id
6c05c2ee-c5a5-4d4e-83a9-b65688fca6df, time is 11/10/2018 2:16:57 AM