A simple azure function, triggered by cosmos that logs to blob storage

azure-function-cosmos-trigger.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using Microsoft.Azure.Documents;
using Microsoft.Azure.WebJobs;
using Microsoft.Extensions.Logging;
using Microsoft.WindowsAzure.Storage.Blob;

namespace CosmosDbChangeFeedTrigger
{
    public static class CosmosDbChangeFeedTrigger
    {
        [FunctionName("<put azure function name here")]
        public static void Run([CosmosDBTrigger(
            "<put database name here>",
            "<put collection name here>",
            ConnectionStringSetting = "<put cosmos db connection string name here",
            LeaseCollectionName = "<put leases collection name here>",
            CreateLeaseCollectionIfNotExists = true)]IReadOnlyList<Document> documents,
            [Blob("test-database-container", FileAccess.Write)] CloudBlobContainer container,
            ILogger log)
        {
            log.LogInformation("Starting the function....");
            log.LogInformation("Saving data...");
            documents.ToList().ForEach(d => writeToBlobStorage(container, d));
            log.LogInformation("Data saved, exiting.");
        }

        private static void writeToBlobStorage(CloudBlobContainer container, Document d)
        {
            var fileName = string.Format("log-file-{0}.json",d.Id);
            Console.WriteLine("Uploading to Blob storage as {0}...", fileName);

            CloudBlockBlob cloudBlockBlob = container.GetBlockBlobReference(fileName);
            cloudBlockBlob.UploadTextAsync(d.ToString()).Wait();
        }
    }
}

The "Blob" attribute is an "out" binding. Together with the FileAccess enum it gives access to a CloudBlobContainer instance. This instance can be used to access blob storage