C# – Azure WebJobs – No functions found – How to make a trigger-less job

azureazure-webjobsc

I'm new to Azure WebJobs, I've run a sample where a user uploads an image to blob storage and inserts a record into the Queue, then the job retrieves that from the queue as a signal to do something like resizing the uploaded image. Basically in the code the job uses QueueTrigger attribute on a public static method to do all that.

Now I need a job that just does something like inserting a record into a database table every hour, it does not have any type of trigger, it just runs itself. How do I do this?

I tried to have a static method and in it I do the insert to db, the job did start but I got a message saying:

No functions found. Try making job classes public and methods public
static.

What am I missing?

Edit
After Victor's answer I tried the following,

static void Main()
{
    JobHost host = new JobHost();
    host.Call(typeof(Program).GetMethod("ManualTrigger"));
}

[NoAutomaticTrigger]
public static void ManualTrigger()
{
    // insert records to db
}

but this time I got InvalidOperationException,

'Void ManualTrigger()' can't be invoked from Azure WebJobs SDK. Is it missing Azure WebJobs SDK attributes?

Best Answer

If you don't use any input/output attributes from the WebJobs SDK (QueueTrigger, Blob, Table, etc), you have to decorate the job with the NoAutomaticTrigger Attribute to be recognized by the SDK.

Method A: HttpClient (Preferred)

Available in: .NET Framework 4.5+, .NET Standard 1.1+, .NET Core 1.0+ .

It is currently the preferred approach, and is asynchronous and high performance. Use the built-in version in most cases, but for very old platforms there is a NuGet package.

using System.Net.Http;

Setup

It is recommended to instantiate one HttpClient for your application's lifetime and share it unless you have a specific reason not to.

private static readonly HttpClient client = new HttpClient();

See HttpClientFactory for a dependency injection solution.

POST

var values = new Dictionary<string, string>
{
    { "thing1", "hello" },
    { "thing2", "world" }
};

var content = new FormUrlEncodedContent(values);

var response = await client.PostAsync("http://www.example.com/recepticle.aspx", content);

var responseString = await response.Content.ReadAsStringAsync();

GET

var responseString = await client.GetStringAsync("http://www.example.com/recepticle.aspx");

Method B: Third-Party Libraries

RestSharp

POST

 var client = new RestClient("http://example.com");
 // client.Authenticator = new HttpBasicAuthenticator(username, password);
 var request = new RestRequest("resource/{id}");
 request.AddParameter("thing1", "Hello");
 request.AddParameter("thing2", "world");
 request.AddHeader("header", "value");
 request.AddFile("file", path);
 var response = client.Post(request);
 var content = response.Content; // Raw content as string
 var response2 = client.Post<Person>(request);
 var name = response2.Data.Name;

Flurl.Http

It is a newer library sporting a fluent API, testing helpers, uses HttpClient under the hood, and is portable. It is available via NuGet.

    using Flurl.Http;

POST

var responseString = await "http://www.example.com/recepticle.aspx"
    .PostUrlEncodedAsync(new { thing1 = "hello", thing2 = "world" })
    .ReceiveString();

GET

var responseString = await "http://www.example.com/recepticle.aspx"
    .GetStringAsync();

Method C: HttpWebRequest (not recommended for new work)

Available in: .NET Framework 1.1+, .NET Standard 2.0+, .NET Core 1.0+. In .NET Core, it is mostly for compatibility -- it wraps HttpClient, is less performant, and won't get new features.

using System.Net;
using System.Text;  // For class Encoding
using System.IO;    // For StreamReader

POST

var request = (HttpWebRequest)WebRequest.Create("http://www.example.com/recepticle.aspx");

var postData = "thing1=" + Uri.EscapeDataString("hello");
    postData += "&thing2=" + Uri.EscapeDataString("world");
var data = Encoding.ASCII.GetBytes(postData);

request.Method = "POST";
request.ContentType = "application/x-www-form-urlencoded";
request.ContentLength = data.Length;

using (var stream = request.GetRequestStream())
{
    stream.Write(data, 0, data.Length);
}

var response = (HttpWebResponse)request.GetResponse();

var responseString = new StreamReader(response.GetResponseStream()).ReadToEnd();

GET

var request = (HttpWebRequest)WebRequest.Create("http://www.example.com/recepticle.aspx");

var response = (HttpWebResponse)request.GetResponse();

var responseString = new StreamReader(response.GetResponseStream()).ReadToEnd();

Method D: WebClient (Not recommended for new work)

This is a wrapper around HttpWebRequest. Compare with HttpClient.

Available in: .NET Framework 1.1+, NET Standard 2.0+, .NET Core 2.0+

using System.Net;
using System.Collections.Specialized;

POST

using (var client = new WebClient())
{
    var values = new NameValueCollection();
    values["thing1"] = "hello";
    values["thing2"] = "world";

    var response = client.UploadValues("http://www.example.com/recepticle.aspx", values);

    var responseString = Encoding.Default.GetString(response);
}

GET

using (var client = new WebClient())
{
    var responseString = client.DownloadString("http://www.example.com/recepticle.aspx");
}

C# – Dependency injection using Azure WebJobs SDK

Azure WebJobs SDK now supports instance methods. Combining this with a custom IJobActivator allows you to use DI.

First, create the custom IJobActivator that can resolve a job type using your favourite DI container:

public class MyActivator : IJobActivator
{
    private readonly IUnityContainer _container;

    public MyActivator(IUnityContainer container)
    {
        _container = container;
    }

    public T CreateInstance<T>()
    {
        return _container.Resolve<T>();
    }
}

You need to register this class using a custom JobHostConfiguration:

var config = new JobHostConfiguration
{
    JobActivator = new MyActivator(myContainer)
};
var host = new JobHost(config);

Then, you can use a simple class with instance methods for your jobs (here I'm using Unity's constructor injection feature):

public class MyFunctions
{
    private readonly ISomeDependency _dependency;

    public MyFunctions(ISomeDependency dependency)
    {
        _dependency = dependency;
    }

    public Task DoStuffAsync([QueueTrigger("queue")] string message)
    {
        Console.WriteLine("Injected dependency: {0}", _dependency);

        return Task.FromResult(true);
    }
}

Best Answer

Related Solutions

C# – How to make an HTTP POST web request

Method A: HttpClient (Preferred)

Setup

Method B: Third-Party Libraries

Method C: HttpWebRequest (not recommended for new work)

Method D: WebClient (Not recommended for new work)

C# – Dependency injection using Azure WebJobs SDK

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