Azure Functions v2 with .NET Core - billing in serverless architecture.
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README.md

Azure Functions v2 with .NET Core

This example shows simplified billing system in serverless architecture.

Comprehensive guide describing exactly the architecture, applied design patterns and technologies can be found on our blog in article Azure Functions 2.0 – real world use case for serverless architecture.

We encourage you to read, because in this README there is only a substitute for all information.

Architecture

  1. User uploads CSV file (with name structure CLIENTCODE_YEAR_MONTH_activeList.txt.) with Beneficiaries (the sample file is located in the data-examples folder) to a specific data storage - active-lists Azure Blob Container.

  2. The above action triggers a function (GenerateBillingItemsFunc) that is responsible for:

    • generating billing items (using prices from an external database - CosmosDB crm database, prices collection) and saving them in the table billingItems;
    • sending message about the need to create a new invoice to invoice-generation-request;
  3. When a new message appears on the queue invoice-generation-request, next function is triggered (GenerateInvoiceFunc). This function creates domain object Invoice and save this object in database (CosmosDB crm database, invoices collection) and send message to queues: invoice-print-request and invoice-notification-request.

  4. When a new message appears on the queue invoice-print-request, function PrintInvoiceFunc is triggered. This function uses external engine to PDF generation - JsReport and saves PDF file in BLOB storage.

  5. When a new message appears on the queue invoice-notification-request, function NotifyInvoiceFunc is triggered. This function uses two external systems - SendGrid to Email sending and Twilio to SMS sending.

Tutorial from scratch to run locally

  1. Install and run Microsoft Azure Storage Emulator.

  2. Install and run CosmosDB Emulator. Check this on https://localhost:8081/_explorer/index.html.

  3. Create in Emulator blob Container active-lists.

  4. Upload ASC_2018_02_activeLists.txt file from data-examples folder to active-lists blob.

  5. Create CosmosDB database crm and in this database create collections: prices, invoices.

  6. Add CosmosDB properties PriceDbUrl and PriceDbAuthKey to local.appsettings.json in PriceDbInitializator and GenerateBillingIemsFunc. You can copy this properties from Azure CosmosDB Emulator - check point 2 (URI and Primary Key).

  7. Run project PriceDbInitializator to init collection prices in crm database.

  8. Add CosmosDB connection string as cosmosDb to local.settings.json in GenerateInvoiceFunc. You can copy this string from Azure CosmosDB Emulator - check point 2 (Primary Connection String).

  9. Create an account in SendGrid and add property SendGridApiKey to local.settings.json in NotifyInvoiceFunc.

  10. Create an account in Twilio and add properties TwilioAccountSid TwilioAuthToken to local.settings.json in NotifyInvoiceFunc.

  11. Run JsReport with Docker: docker run -p 5488:5488 jsreport/jsreport. Check JsReport Studio on localhost:5488.

  12. Add JsReport url as JsReportUrl to local.settings.json in PrintInvoiceFunc project.

  13. Add JsReport template with name INVOICE and content:

<h1>Invoice {{invoiceNumber }}</h1>
<h3>Customer: {{ customer }}</h3>
<h3>Address: 00-101 Warszawa, Chłodna 21</h3>
<h3>Description: {{ description }}</h3>

<h3>Details:</h3>
<table width="90%" border="1" bgcolor="#C0C0C0" align="center">
    <tr>
        <th>Item</th>
        <th>Price</th>
    </tr>

    {{#each lines}}
    <tr>
        <td>{{ itemName }}</td>
        <td align="right">{{ cost }}</td>
    </tr>
    {{/each}}

    <tr>
        <td>
            <strong>Total</strong>
        </td>
        <td align="right">
            <strong>{{ totalCost }}</strong>
        </td>
    </tr>
</table>

Example JSON for INVOICE template:

{
  "customer": "ASC",
  "invoiceNumber": "ASC/10/2018",
  "description": "Invoice for insurance policies for 10/2018",
  "lines": [
    {
      "itemName": "Policy A",
      "cost": 2140.0
    },
    {
      "itemName": "Policy B",
      "cost": 1360.0
    }
  ],
  "totalCost": 3500.0
}

All properties in one local.appsettings.json:

{
  "IsEncrypted": false,
  "Values": {
    "FUNCTIONS_WORKER_RUNTIME": "dotnet",
    "AzureWebJobsStorage": "UseDevelopmentStorage=true",
    "PriceDbUrl": "https://localhost:8081",
    "PriceDbAuthKey": "AUTH_KEY",
    "cosmosDb": "AccountEndpoint=https://localhost:8081/;AccountKey=AUTH_KEY",
    "JsReportUrl": "http://localhost:5488",
    "SendGridApiKey": "SEND_GRID_API_KEY",
    "TwilioAccountSid ": "TWILIO_ACCOUNT_SID",
    "TwilioAuthToken": "TWILIO_AUTH_TOKEN"
  }
}

Monitoring examples

Application Map for all function in one project:

Application Map 1

Application Map for functions in separated projects:

Application Map 2

End-to-end transaction details:

End to End Transaction Details

Tips & Tricks

  1. CSV file is working for client code ASC (filename: ASC_2018_12_activeList.txt). If you want run functions for another client code, you must simulate prices in database. Check project PriceDbInitializator, file Program.cs, method AddDoc.

  2. Remember that you must use Twilio Test Credentials.

Twilio Test Credentials

  1. Microsoft Azure Storage Emulator with all created storages:

Microsoft Azure Storage Emulator