title: How to avoid failed when input blob is missing in Azure Data Factory copy activity
body: <p>I have a pipeline with three activities:
   1. Download file from external web site and store it in blob storage (custom activity)
   2. Copy data from blob to Azure SQL DB (Copy activity)
   3. Delete blob file (custom activity)</p>
  
  <p>The files shall be downloaded once/month, but I don't know which day it will be made available, so I have scheduled the pipeline to run once/day. If the file is available, it is downloaded. Activity #1 works fine, but activity #2 fails if there is no input file. Is there any way to avoid the Failed result, since it's an expected outcome?</p>