Fix race that causes "lease id cannot be null or empty" illegal argument exception from storage

[JamesBirdsall]

Problem occurs in acquireLease and is a race condition that requires multiple instances of EventProcessorHost and storage calls to be interleaved in a particular order.

When this instance of EventProcessorHost scanned the lease blobs, this partition was unowned (token is empty) but between then and now, another instance of EPH has established a lease (getLeaseState() is LEASED). We normally enforce that we only steal the lease if it is still owned by the instance which owned it when we scanned, but we can't do that when we don't know who owns it. The safest thing to do is just fail the acquisition. If that means that one EPH instance gets more partitions than it should, rebalancing will take care of that quickly enough.

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[msftclas]

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[serkantkaraca]

		throw new IllegalArgumentException("acquireLeaseSync: newLeaseId really is " + ((newLeaseId == null) ? "null" : "empty"));

James, I thought this was throwing, no? #Closed

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Refers to: azure-eventhubs-eph/src/main/java/com/microsoft/azure/eventprocessorhost/AzureStorageCheckpointLeaseManager.java:394 in 50fb1db. [](commit_id = 50fb1db, deletion_comment = False)

[JamesBirdsall]

No, that message did not appear in the logs. Also, if that line threw, then the storage call which did throw and did appear in the logs would not have been made.

[serkantkaraca]

lease.getToken() [](start = 92, length = 16)

Due to the same race, this can still throw NullRef, right? #Closed

[JamesBirdsall]

getToken() does not fetch anything from Storage, it just returns the string currently stored in the Lease. That string does not change unless the instance is replaced or setToken() is called. In this case, all three calls to getToken() are guaranteed to return the same value.

[serkantkaraca]