This is not a guide or any kind of introduction to Logic Apps but my thoughts and key take aways from working with them for a while now.
Events & Connectors
Logic Apps are great for reacting to events – especially Azure events – and I usually use them to build up the outer and more general logic of a system. This is to react to things that happens and maybe do comparison against thresholds and other configuration settings. It’s easy to call out to other services both in Azure, Office and external APIs.
As a general rule I don’t use Logic Apps to update data – I prefer to use Azure Functions for that as SDKs usually supports more advanced retries and error handling. However, some connectors supports this also – your mileage may vary.
The connectors really are the stars of Logic Apps – you can receive and act on data from pretty much any resource in the Microsoft eco system and most enterprise systems that support Azure Active Directory have connectors too.
Creating Logic Apps using the visual designer in the Portal and Visual Studio is a breeze – Visual Studio Code still only supports editing the underlying JSON document but will display the visual designer in read-only mode. Actual development using a repo and Azure DevOps CI/CD is a bit clunky and deployment requires an ARM template to be built using a script. Better support for storing the “code” for a Logic App in a code repository and deployment is something I’m hoping that will be added in the future.
I’ve seen integration developers use Logic Apps to quickly and easily build integration pipelines using HTTP, data parsing, conditions and service bus but they get stuck when it comes to CI/CD.
No deployment slots
Logic Apps doesn’t support deployment slots so it requires a service window of some sort when deploying in higher load scenarios. Since we’re exposing our Logic Apps through the Azure API Management Gateway we mock the requests to our Logics Apps during deployments. This is certainly not ideal and I hope that Logic Apps will get some form of deployment slot capability in the future.
Logic Apps on paper supports reacting to and handling 1000s of events and requests per minute (we’ve done that too – Just be aware that the normal limit is 100.000 requests per 5 minutes). However if you’re not carefull then “long” running activations during high load can cause your entire App to freeze. If this happens then a manual restart can become required. If that happens then you have to start thinking about your usage of Logic Apps; the flows, branching, error handling and perhaps if moving to an Azure Function is better fit for what you’re trying to accomplish.