Azure Function CosmosDB Trigger returned encoded data?

Question

I wrote a short azure function to simply take data in from CosmosDB change feed Trigger.

However, looks like it returns some form of encoded data.

For example

{
    "_id" : ObjectId("5ad8db107dfa95101430ab94"),
    "id" : "task123",
    "type" : "genera123l",
    "information" : "some task"
}

If above document is created in my cosmos db,

public static void Run(IReadOnlyList<Document> documents, TraceWriter log)
{
    if (documents != null && documents.Count > 0)
    {
        log.Info("Documents modified " + documents.Count);
        log.Info("First document Id " + documents[0].Id);
    }
}

above code will print

2018-04-19T19:28:23.899 [Info] Documents modified 1
2018-04-19T19:28:23.899 [Info] First document Id NWFkOGRiMTA3ZGZhOTUxMDE0MzBhYjk0

instead of

2018-04-19T19:28:23.899 [Info] Documents modified 1
2018-04-19T19:28:23.899 [Info] First document Id task123

which is the expected output. Is there some sort of configuration that I'm missing here?

Looks like none of the documentations for CosmosDB or Azure Function App addresses this issuse :(

Thanks

Appears that the Id value is coming from '_id', instead of 'id' parameter of the document. decoding in base64 created correct value for _id. appears that its being read as ObjectId, — Evan Park

Tom Sun - MSFT Tom Sun - MSFT · Accepted Answer · 2018-04-20T06:25:51

I assume that you use the Azure CosmosDB MongoDb API for input bindings.

Please hava a try to use the Azure CosmosDB SQL API. Detail steps you could refer to this guide. Then you could get the expected answer. For more information, please refer to this link.

Don't use Azure Cosmos DB input or output bindings if you're using MongoDB API on a Cosmos DB account. Data corruption is possible.

Azure Function CosmosDB Trigger returned encoded data?

2 Answers