In the Azure portal, we need to create a function app for creating Azure Functions. A function app provides the execution context for individual functions. All configuration done at the function-app level will be applied to all Azure Functions. The following is an example of an Azure Function app named ShipAnyWhere-AzureFunction and a function called UpdateInventory:

These function apps are run and maintained by the Azure App Service platform, which is an Azure service used for hosting web applications, REST APIs, and mobile backends. The following is a layer diagram showing the dependencies of an Azure Functions runtime over other Azure technologies:

From the preceding diagram, it is clear that the root of Azure Functions is the Azure App Service platform, which brings following core capabilities to Azure Functions:

• It provides the ability...

To explain the concepts of Azure Functions, we'll make use of a fictional company, ShipAnyWhere. ShipAnyWhere is a large logistical company that is specialized in commerce and fulfillment. ShipAnyWhere provides solutions for e-commerce businesses across the world. It has got more than 100 distribution centers across more than 30 countries. It provides B2B, e-commerce, and multi-channel fulfillment solutions to its customers using cutting-edge technologies.

ShipAnyWhere has a web application that allows orders to be submitted by customers. When an order is submitted, the following takes place:

1. The web application puts the Order message in a Service Bus queue
2. An Azure Function receives the Order messages from the Service Bus queue
3. The availability of the products being ordered is checked with Inventory DB, which is a Cosmos DB database collection
4. Based...

In the previous section, we implemented the first part of our scenario by creating an Azure Function with a Service Bus queue trigger and running it locally. At this point, it is essential that we understand the various components of Azure Functions.

The host.json file is a configuration file containing the values that affect all the functions of a function app. This file is created as soon as we add an Azure Function project. This file will have at least one field to begin with, indicating the runtime version of Azure Functions.

The following is the content of the host.json file created in our sample project:

In the first part of the sample scenario, we created an Azure Function with a Service Bus trigger, ran the function locally, and deployed it to an Azure Function app. In this section, we will implement the logic for validating orders against Inventory DB and updating the order in Sales DB:

To install the NuGet package, you need to do the following:

1. Press F1 in Visual Studio Code for the command pallet
2. Select the option for installing a NuGet package:

3. Select the package named Microsoft.Azure.WebJobs.Extensions.CosmosDB:

Due to the ease of use and availability of a diverse set of triggers and bindings for Azure Functions, Azure Functions are being used more and more in various use cases. In this section, we will see some of the use cases in which Azure Functions can be used.

Again, we make use of our fictional company, ShipAnyWhere, to explain some use cases:

• Extending Logic Apps functionality: ShipAnyWhere has a logic app that processes orders. Though the transformation is done by executing maps, the order needs to be further enriched with master data lookups. The master data lookup is a functionality that will be shared across various integrations. ShipAnyWhere has decided to use Azure Functions to implement the lookup logic. Using Azure Function connectors, Logic Apps can make use of this lookup functionality:

• Extending SaaS applications: At ShipAnyWhere, the invoices...

Azure Functions provide a rich set of functionalities to build enterprise-grade serverless functions. Though it is easy to create simple functions easily, when making enterprise-grade functions we need to follow some best practices. In this section, we are going to discuss a few best practices when implementing Azure Functions.

In our samples, we stored two connection strings: one for the Service Bus queue and another one for Cosmos DB. Both these application settings carry keys, which are sensitive and need to be secured in one place. Azure Key Vault is the best place to store any secrets. Storing connection strings...

Durable Functions is an extension to Azure Functions that allows us to create code-based workflows by managing state, checkpoints, and restarts. Logic apps, on the other hand, provide all this functionality in a designer-based approach. The following are some of the patterns durable functions help us to achieve in code-based integrations.

A pattern formed by the execution of multiple microservices – in this case, Azure Functions – in a sequential order is referred to as function chaining:

In the preceding example, there is a Orchestrator function, which executes the Activity Functions – Func1, Func2, Func3, and Func4 – in a sequential manner. The state of every...

In this section, we will implement a function-chaining scenario. At ShipAnyWhere, when a new driver registers themselves, there are a few things that need to happen in a sequential manner. First, the driver's background needs to be verified. If the verification result is successful, they can be registered as a contract employee and assigned a driver ID. Once the driver ID is created, induction training will be scheduled. All these tasks are dependent on each other and are long running. Hence, we will implement the flow using durable functions.

In Visual Studio Code, press F1 to open the command pallet. Use the NuGet package install command and provide...

Azure Functions are the linchpin in Azure's serverless offerings. With a range of triggers and bindings available, it is quick and easy for developers to spin up Azure Functions for given problems or APIs. Microsoft has made it possible for users to either use the Azure portal, Visual Studio, or Visual Studio Code for development.

In next chapter we will cover how to use Azure Event Grid and Event Grid Domain to publish and subscribe events from client application. We will also cover how you can utilize Azure Functions bindings to publish and subscribe events from Event Grid.