Publish to an Azure Event Hub with output bindings and use partition keys

Question

I'm publishing an object to an Azure Event Hub using output bindings like so.

[FunctionName("IntegrationFunction")]
[return: EventHub("%Transactions:EVH:Transactions:Hub%", Connection = "Transactions:EVH:Transactions")]
public Transaction Run(
    [ServiceBusTrigger(
        "%Transactions:SB:Transactions:ReceiveTopic%",
        "%Transactions:SB:Transactions:AnalyticsTopicSubscription%",
        Connection = "Transactions:SB:Transactions")]
    string mySbMsg,
    ILogger log)
{
    var retailTransaction = JsonConvert.DeserializeObject<RetailTransaction>(
        mySbMsg,
        JsonSerialisationUtils.SerialiserSettings);
    
    try
    {
        var transaction = retailTransaction.ToDto();
        log.LogInformation($"Transaction {transaction.TransactionNumber} processed.");
        return transaction;
    }
    catch (Exception e)
    {
        log.LogError(e, "Error mapping transaction.");
    }

    return null;
}

Is there any way to publish it to a specific partition e.g. transaction.StoreCode?

Answer 1

You can pass the partition key value while publishing the events to EventHub using IAsyncCollector<EventData>. Refer the MSDoc and github issue for more details.

• I am using the below code to set the partition key.

using System;
using System.Text;
using System.Threading.Tasks;
using Azure.Messaging.EventHubs;
using Microsoft.Azure.WebJobs;
using Microsoft.Azure.WebJobs.EventHubs;
using Microsoft.Azure.WebJobs.Host;
using Microsoft.Extensions.Logging;
namespace _78148689
{
    public class Function1
    {
        [FunctionName("IntegrationFunction")]
        public static async Task Run([ServiceBusTrigger("mytopic", "mysubscription", Connection = "serviceBusConnection")]string mySbMsg,
            [EventHub("test-hub", Connection = "EventHubConnectionAppSetting")]IAsyncCollector<EventData> outputEvents, ILogger log)
        {
            log.LogInformation($"C# ServiceBus topic trigger function processed message: {mySbMsg}");

            var eventData = new EventData(Encoding.UTF8.GetBytes(mySbMsg));

            await outputEvents.AddAsync(eventData, "demo-key");
        }
    }
}

.csproj-

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>net6.0</TargetFramework>
    <AzureFunctionsVersion>v4</AzureFunctionsVersion>
    <RootNamespace>_78148689</RootNamespace>
  </PropertyGroup>
  <ItemGroup>
    <PackageReference Include="Azure.Messaging.EventHubs" Version="5.11.1" />
    <PackageReference Include="Microsoft.Azure.WebJobs.Extensions.EventHubs" Version="6.2.0" />
    <PackageReference Include="Microsoft.Azure.WebJobs.Extensions.ServiceBus" Version="5.13.6" />
    <PackageReference Include="Microsoft.NET.Sdk.Functions" Version="4.3.0" />
  </ItemGroup>
  <ItemGroup>
    <None Update="host.json">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </None>
    <None Update="local.settings.json">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
      <CopyToPublishDirectory>Never</CopyToPublishDirectory>
    </None>
  </ItemGroup>
</Project>

I am able to publish the event.