CODEWITHSUNDEEP
azureazure-functionsazure-cosmosdb
tnk479
tnk479

Reputation: 794

How do I pass in the storage account connection string for a CosmosDBTrigger?

I'm trying to figure out the proper way to pass in a storage account connection string to a CosmosDBTrigger. I have a function that runs when there is a change on a CosmosDB container. This function copies image blobs from one container to another. If you look at the code below, I have commented out the line where I am trying to fine the storage account that I want to connect to. This function runs when that is commented out. It does not run when I have that un-commented. Why?

public static class Function1
{
    [FunctionName("ImageCopier")]
    public static async Task Run([CosmosDBTrigger(
        databaseName: "MyDatabase", 
        collectionName: "Orders",
        ConnectionStringSetting = "databaseConnection",
        CreateLeaseCollectionIfNotExists = true,
        LeaseDatabaseName = "TriggerLeases",
        LeaseCollectionName = "TriggerLeases",
        LeaseCollectionPrefix = "ImageCopier")]IReadOnlyList<Document> input, 
        //[StorageAccount("MyStorageAccount")]string storageConnectionString,
        ILogger log)
    {

I have MyStorageAccount defined in my local.settings.json file and I also have it in my Azure Function Configuration settings. I copied the connection string directly from the storage account keys panel.

Upvotes: 1

Views: 390

Answers (2)

Noah Stahl
Noah Stahl

Reputation: 7623

While you can access raw configuration values using GetEnvironmentVariable, a more robust/idiomatic approach with .NET in particular is to leverage the built-in dependency injection of configuration.

Using this, you can accept an IConfiguration or strongly-typed IOptions through the function's constructor and use the values in your code. For example:

public class Function1
{
    private readonly IConfiguration configuration;

    public Function1(IConfiguration configuration)
    {
        this.configuration = configuration;
    }

    [FunctionName("ImageCopier")]
    public async Task Run([CosmosDBTrigger(/* trigger params */)] IReadOnlyList<Document> input)
    {
        var connectionString = configuration["MyStorageAccount"];

        // Use connection string
    }
}

You can take this further to inject services like an "ImageBlobService" into your function that have already been configured in a common Startup Configure method just like ASP.NET Core. That way the individual functions don't need to know anything about configuration and just ask for the relevant service to use.

Upvotes: 0

Andy
Andy

Reputation: 13607

When you set up a CosmosDB trigger, the information that is supplied in that trigger is specific to the trigger. If you need a setting or configuration not related to the trigger in your code, you can use the Environment.GetEnvironmentVariable method.

In your local environment, you can set these variables by editing the local.settings.json file, specifically the Values array. For example:

{
    "IsEncrypted": false,
    "Values": {
        "JobUri": "https://yourapiendpointurl.com",
        "BlobStorageConnectionString" : "the connection string",
        "AzureWebJobsStorage": "UseDevelopmentStorage=true",
        "FUNCTIONS_WORKER_RUNTIME": "dotnet"
    }
}

In your method, you may grab that value like so:

public static class Function1
{
    [FunctionName("ImageCopier")]
    public static async Task Run([CosmosDBTrigger(
        databaseName: "MyDatabase", 
        ...
        ILogger log)
    {
        var connectionString = 
            Environment.GetEnvironmentVariable("BlobStorageConnectionString");
    }
}

The local.settings.json file will not be used when it's running in Azure.

I am not sure that when you publish the function if your local.settings.json file will migrate the settings to your Azure Function app's configuration, so I would check to make sure that your settings are in there after publishing.

Side note: Be carful when committing code to repos .. you don't want "secrets" in your repositories in case someone gets in to your repo and discovers it.

Upvotes: 0

Related Questions