Azure Service Bus: High Availability

Question

I'm currently building a hybrid-cloud solution that needs to write messages to a queue for later processing. It is absolutely imperative that the queue is highly available (99.999+% uptime).

My options are to read/write messages to a local ZeroMQ high availability pair, or an Azure Service Bus. I would prefer to go the Azure Service Bus route, but can't find any documentation regarding high availability configuration for Azure Service Bus.

Has anyone had success setting up Azure Service Bus for high availability? I understand that the SLA for a single instance of any Azure service cannot be changed. I'm thinking more along the lines of the failover capabilities of Azure Web Apps.

Answer 1

The main thing you can do for consuming a service at a higher than SLA value is to ensure you are handling retry logic. The key here will be the temporal nature of any outage, and tuning a retry backoff to handle edge cases. Some use linear or exponential backoffs to wait even longer for the service to come back up.

Also, you can have more than one service bus in a different region for georedundancy, and either load balancing messages across the two or use one as a hot backup. This can get you around any regional outages and keep your service up when one data center is not meeting its local SLA.

Answer 2

You can find the for SLA for Azure Service Bus here: legal/sla/service-bus/v1_0/

For Service Bus Relays, we guarantee that at least 99.9% of the time, properly configured applications will be able to establish a connection to a deployed Relay. For Service Bus Queues and Topics, we guarantee that at least 99.9% of the time, properly configured applications will be able to send or receive messages or perform other operations on a deployed Queue or Topic. For Service Bus Basic and Standard Notification Hub tiers, we guarantee that at least 99.9% of the time, properly configured applications will be able to send notifications or perform registration management operations with respect to a Notification Hub. For Event Hubs Basic and Standard tiers, we guarantee that at least 99.9% of the time, properly configured applications will be able to send or receive messages or perform other operations on the Event Hub.

Answer 3

Service Bus now supports Geo-disaster recovery and Geo-replication at the namespace level.

https://learn.microsoft.com/en-us/azure/service-bus-messaging/service-bus-geo-dr

Answer 4

We've had Service Bus Relay up and running for 5+ years and have had one outage. It was an outage at the specific data center the relay was provisioned in and touched many services. After that we implemented redundancy by implementing a secondary Service Bus Relay namespace in a different data center location. The reconfigured code was set to check the connectivity on every connection and switch the primary and secondary connections. We treated them as equals so once we "failed over" that namespace would become primary.