azure-webjobs-sdk-extensions: Function app settings not read when a function is developed in portal using Cosmos DB Trigger

From @baskar3078 on November 1, 2017 2:49

When we develop a function using Cosmos DB Trigger in azure portal, the database and collection names are not read from function application settings in function.json file.

Investigative information

Repro steps

  1. Create a function using CosmosDB Trigger portal
  2. Add an function application setting with Key - “cosmos-triggers-database-name” and any value
  3. Update the function.json as below
  "bindings": [
      "type": "cosmosDBTrigger",
      "name": "inputDocs",
      "direction": "in",
      "leaseDatabaseName": "leases",
      "leaseCollectionName": "MyCosmosCollection-myFunction",
      "connectionStringSetting": "CosmosTriggers-SourceAdapter",
      "databaseName": "%cosmos-triggers-database-name%",
      "collectionName": "MyCosmosCollection",
      "createLeaseCollectionIfNotExists": true
  "disabled": false
  1. Save and run the function

Expected behavior

Expected behavior is to read the document from Cosmos DB.

Actual behavior

Function ($myFunction) Error: The listener for function 'Functions.myFunction' was unable to start.
 Microsoft.Azure.WebJobs.Extensions.DocumentDB: Either the source collection 'MyCosmosCollection' (in database '%cosmos-triggers-database-name%') or the lease collection 'MyCosmosCollection-myFunction' (in database 'leases') does not exist. Both collections must exist before the listener starts. To automatically create the lease collection, set 'CreateLeaseCollectionIfNotExists' to 'true'. Microsoft.Azure.Documents.Client: Message: {"Errors":["Resource Not Found"]}
 ActivityId: b00f7802-fccb-47eb-972d-0bd70ec896c1, Request URI: rntbd://
 Session Id: 092ccb7ce9104407bf56c26a5cc8b119
 Timestamp: 2017-10-31T19:13:03.914Z

Known workarounds

We need to explicitly mention the database and collection name in function.json file.

Related information

Copied from original issue: Azure/azure-webjobs-sdk-script#2086

About this issue

  • Original URL
  • State: closed
  • Created 7 years ago
  • Reactions: 1
  • Comments: 17 (14 by maintainers)

Most upvoted comments

I was confused as well. I took a look and have submitted #370 which should fix it.

There were 2 things:

  • The NameResolver keys won’t contain %%. They basically just do a straight lookup. That’s why the tests passed.
  • You need to use the ResolveWholeString extension in order to evaluate with the %%.