Consumer Group Limits per Namespace

Question

Hello,

we are thinking of using Event Hubs Premium or Dedicated to host an Event Hubs namespace for our project. We would prefer a single namespace to allow all consumers to subscribe to any topics.

The Event Hubs tier comparison page states:

Number of consumer groups per event hub

Basic|Standard|Premium|Dedicated

|1|20|100|1,000 No limit per CU

Number of Kafka consumer groups per namespace

Basic|Standard|Premium|Dedicated

NA|1,000|1,000|1,000

How is the number of consumer groups per namespace defined? Is it just the sum of all consumer groups in all event hubs of the specific namespace? Or is some form of uniqueness (e.g. consumer group names) counted?

So in theory: a namespace with 100 event hubs and 10 consumer groups per event hub would reach the limit of 1000 consumer groups per namespace?

Can the limit be increased somehow per support request based on the number of purchased PUs/CUs?

Thanks

Answer 1

Hi @KE
Thank you for posting your query!

In addition to Sander van de Velde | MVP response
In Azure Event Hubs, the number of consumer groups is limited per event hub, not per namespace. This means each event hub within a namespace can have up to the maximum allowed consumer groups independently. For example, in the Premium tier, each event hub can have up to 100 consumer groups, and in the Dedicated tier, up to 1,000 consumer groups per event hub.

Is it just the sum of all consumer groups in all event hubs of the specific namespace?
Event Hubs consumer groups: No, the limit is per event hub, not per namespace. The total number of consumer groups in a namespace is not restricted, as long as each event hub stays within its tier limit.
Kafka consumer groups: Yes, the limit is per namespace, meaning all Kafka consumer groups across all event hubs in the namespace count toward the 1,000 limit (for Standard, Premium, and Dedicated tiers).

A namespace with 100 event hubs and 10 consumer groups per event hub would reach the limit of 1000 consumer groups per namespace?

Event Hubs consumer groups: No, you would not hit a limit because the consumer group limit applies per event hub, not per namespace. In this case, each event hub has 10 consumer groups, which is well below the limits for all tiers.
Kafka consumer groups: Yes, you would hit the limit because Kafka consumer groups have a namespace-level limit of 1,000 in Standard, Premium, and Dedicated tiers.

Can the limit be increased somehow per support request based on the number of purchased PUs/CUs?
For Event Hubs consumer groups, the per-event hub limit (e.g., 100 for Premium, 1,000 for Dedicated) cannot be increased beyond its tier’s maximum. However, in Dedicated clusters, where there is no limit per Capacity Unit (CU), adding more CUs may effectively increase the number of consumer groups per event hub.
The 1,000 Kafka consumer group limit per namespace cannot be increased, even in the Dedicated tier.

You can refer the Microsoft Doc below:
https://learn.microsoft.com/en-us/azure/event-hubs/event-hubs-quotas

Hope this helps. Do let us know if you any further queries.

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Answer 2

Hello @KE,

welcome to this moderated Azure community forum.

Although an EventHub namespace supports both connectivity using the EventHub messaging library and the Kafka way of messaging, these are different solutions with different rules and limitations.

Check out this FAQ:

They span a namespace. Using the same Kafka group name for multiple applications on multiple topics means that all applications and their Kafka clients will be rebalanced whenever only a single application needs rebalancing. Choose your group names wisely.

So the EventHub namespace is in control of the limitation.

I'm not sure if this is a hard limit.

You need to ask Microsoft for hard and soft limits via a support ticket.

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