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;
}
}
}
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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