Using Deployment Slots with Event Hub Integrated App Services

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Using Deployment Slots with Event Hub Integrated App Services

CareyBoldenow 96

We have several Java Spring Boot based App Services that are solely integrated with Event Hub to publish and/or consume events. We would like to leverage Deployment Slots to do some level of Blue/Green deployments with these apps, but given the nuances of event driven architecture (e.g. no HTTP, how to maintain consumer group integrity, etc), this is proving to be a bit challenging. I have seen this link which discusses how this could potentially be done with Azure Functions that are integrated with Event Hub: https://stackoverflow.com/questions/64170709/using-azure-function-deployment-slots-with-eventhub, but this solution assumes you are using App Settings to configure things such as consumer groups. In our case, we are using App Configuration for all our application configuration and before we look to move some app properties back to App Settings (which I would prefer not to do), I just wanted to see if any of you have solved this challenge of using Deployment Slots with App Services that are integrated with Event Hub.

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Ryan Hill 30,281 Microsoft Employee Moderator

Hi @CareyBoldenow ,

Have looked into using feature flag management between your Blue/Green deployment slots? This tutorial goes over how to implement for a Java Spring Boot app. Another option you could leverage is labeling your app config. Personally, I've used it to switch between a production and test service bus. I can't think of a reason why that wouldn't work for event hub.

CareyBoldenow 96 Reputation points

2021-10-06T14:19:29.843+00:00

Hello @Ryan Hill ,

Both of these options are very interesting and I guess I would like to learn a bit more about exactly how you might use either feature flags and how you are using labels today to do this with Service Bus. We do use labels (represent the environment the value is meant for) already for all our app configuration key/values, but for production deployments we could alter our use of labels if need be to support these blue/green deployments. We also use the feature flag capability of App Configuration so are very familiar with that as well.

So for discussion sake, let's say we have a Spring Boot App Service called "myAppService (v1.0)" that is consuming events from "Event Hub A" using consumer-group "myConsumerGroup", and currently v1.0 is running in the production deployment slot. Now, we are being asked to modify some of the business logic in "myAppService". So we make the change and deploy v1.1 of "myAppService" to the staging deployment slot. Where I am still a bit fuzzy and could use your help is given that both of these slots are consuming from the same Event Hub A (or maybe in your mind they are not), how do we use either feature flags or labels to coordinate/facilitate both the validation of v1.1 in staging and the eventual swap to production?

Or are you suggesting that rather than literally use deployment slots, that we would use feature flags for example to achieve somewhat the same blue/green deployment as one would get with deployment slots, but not actually use deployment slots?

Thanks!
Carey
Ryan Hill 30,281 Reputation points Microsoft Employee Moderator

2021-10-07T01:34:40.847+00:00
Hi @CareyBoldenow ,

It really depends on what fits best for your app. Having said that, I'm a C# guy but the same principles should apply. In my situation we used two separate resource groups between testing and dev, so everything was duplicate. Inside the resource group, we had multiple service buses endpoints in the App Config that had a different label applied. From a coding perspective, the filter is an app setting and read in at startup along with the necessary app config values

var label = Environment.GetEnvironmentVariable("AppLabel"); var config = new ConfigurationBuilder().AddAzureAppConfiguration(options => { options.Connect(new Uri(Environment.GetEnvironmentVariable("AppConfigEndpoint")), credentials) .Select("servicebus*", LabelFilter.Null) .UseFeatureFlags(); if(!string.IsNullOrEmpty(label)) { options.Select(KeyFilter.Any, label); } }); builder.Services.Replace(ServiceDescriptor.Singleton(typeof(IConfiguration), config.Build()).AddFeatureManagement();

So, you could have blue/green feature flags along with labels that are tied to the slot. Hope this helps.
CareyBoldenow 96 Reputation points

2021-10-07T12:07:38.18+00:00

Thanks @Ryan Hill ! Will give this a try.

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Using Deployment Slots with Event Hub Integrated App Services

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