COSMOS-DB-TEST

A simple example of using CosmosDB change feed to trigger a function.

The example consists of two functions. The first is triggered by a timer and writes a new document to the CosmosDB database. The second reads the changefeed from the database and operates on the data there.

Local Setup

For this to work locally, follow these steps.

1. Install the CosmosDB Local Emulator.
2. Create a Database matching the databaseName in either function.json file. This is TestDB by default. (These should match so the functions deal with the same database.)
3. Create a collection matching the collectionName in either function.json file. This is MonitoredCollection by default. (These should match so the functions deal with the same database.)
4. Create a local.settings.json file in the root of this directory.

{
  "IsEncrypted": false,
  "Values": {
    "AzureWebJobsStorage": "UseDevelopmentStorage=true",
    "FUNCTIONS_WORKER_RUNTIME": "python",
    "ConnectionString": ""
  }
}

5. Copy the connection string from the CosmosDB Emulator and use it for the ConnectionString value.
6. Use F5 in VSCode to launch the two functions.

Notes

The changefeed includes all updates and creates. It does not include deletes. There is also no way to differentiate between an update and a create. It would be possible to add fields to the document to indicate an update if desired. You could also use a soft-delete flag to indicate deletes if you needed to process those.