Question

You are building a .NET consumer using the change feed processor from the Cosmos DB SDK to process an order-events container. During peak hours, a single processor host cannot keep up, and the change feed estimator reports growing lag. Your monitored container has 6 physical partitions. You deploy 3 additional identical instances of the same application (4 total), all configured with the same processor name, the same lease container, and the same instance-specific 'instanceName'... except two instances were accidentally deployed with an identical 'instanceName'. What is the effect on lease (partition) distribution and processing?

Accepted Answer

The change feed processor uses instanceName to uniquely identify each host; two hosts sharing the same instanceName can cause leases to be reassigned back and forth between them, leading to duplicate processing and unstable distribution.

Answer

instanceName is ignored by the processor; leases are always split evenly by processor name alone, so all 4 instances process correctly regardless of duplicate names.

Answer

The duplicate instanceName causes both affected hosts to be rejected at startup, so only 2 of the 4 instances will acquire leases and process changes.

Answer

Because there are 6 partitions and 4 instances, the processor automatically renames duplicate hosts using a GUID suffix, so distribution is unaffected.