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Jonathan Mourtada
Jonathan Mourtada

Posted on • Originally published at mourtada.se on

Create a simple azure function

#azure #serverless #azurefunctions #dotnet

In this post I’ll show you how to create a simple azure function which is triggered by a http call and logs the requests to an appendblob on azure blob storage.

Create a new project

First of all you will need to create a project. I just used the visual studio project template for azure functions(The Azure SDK is needed). Choose to create a Http trigger function and set the authorization level to anonymous

The code

Once created you will get a stub for a working http trigger function. Below is an example how to log the request to an appendblob.

using System; using System.IO; using System.Threading.Tasks; using Microsoft.AspNetCore.Mvc; using Microsoft.Azure.WebJobs; using Microsoft.Azure.WebJobs.Extensions.Http; using Microsoft.AspNetCore.Http; using Microsoft.Extensions.Logging; using Azure.Storage.Blobs; using System.Globalization; using Azure.Storage.Blobs.Specialized; using Azure.Storage.Blobs.Models; using System.Text; using Microsoft.Extensions.Primitives; using System.Linq; namespace MyAzureFunction { public static class MyAzureFunction { [FunctionName("MyAzureFunction")] public static async Task<IActionResult> Run( [HttpTrigger(AuthorizationLevel.Anonymous, "get", Route = null)] HttpRequest req, [Blob("my-blob-container")] BlobContainerClient container, ILogger log) { var culture = new CultureInfo("sv-SE"); var clientIp = GetClientIp(req.Headers); var logStr = $"{DateTime.Now.ToString("T", culture)} {clientIp}\n"; log.LogInformation(logStr); await container.CreateIfNotExistsAsync(); var blobName = $"access_{DateTime.Now.ToString("d", culture).Replace("-", "")}.log"; var appendBlob = container.GetAppendBlobClient(blobName); await appendBlob.CreateIfNotExistsAsync(); await appendBlob.SetHttpHeadersAsync(new BlobHttpHeaders() { ContentType = "text/plain" }); byte[] blockContent = Encoding.UTF8.GetBytes(logStr); using (var ms = new MemoryStream(blockContent)) { await appendBlob.AppendBlockAsync(ms); } return new OkResult(); } private static string GetClientIp(IHeaderDictionary headers) { headers.TryGetValue("X-Forwarded-For", out StringValues value); var clientIp = value.FirstOrDefault() ?? "missing-ip"; return clientIp; } } }
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The first interesting part is the [Blob("my-blob-container")] BlobContainerClient container. This injects a BlobContainerClient that will be used with our interactions with the blob storage of our configured azure storage account.

It is important to use the new Azure.Storage.Blobs namespace. I had some troubles following old code examples that used deprecated namespaces and types. More information can be found here https://docs.microsoft.com/en-us/azure/azure-functions/functions-bindings-storage-blob-output?tabs=csharp#additional-types.

The function creates an appendblob for every new date and sets the content-type of the blob to text/plain. It then adds a row to the blob for every incoming http get request.

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