-------------------- Work in progress -------------

Migration Service

Edit the paramers as shown below
- Choose the resource group location the same as the cosmos db source and destination
- take a note of the hostname bindings for the migrationwebappclient name which will be used as the client URI used for migration
- the cosmos db account information provided is to store the migration metadata and migration state

After the template is deployed, open the URL for the migration client that you took note of above
Add the migration details needed ( the document age parameter is optional, it will start migrating from the beginning if not provided )

You can scale the number of workers up or down by scaling the migrationwebapp service
If you want to check more migration metrics over time, you can check the custom metrics published to the app insights instance created with by the ARM template
Once the migration is complete, you will need to press complete migration to stop streaming from source to destination

Migrations are live as it streams from the source collection to destination.
Migrations can be paused and resumed
Failed migration can be resumed
Reading from source can be starting from a certain date and that can be used to rollback
The tool can be scaled up and down manually during migration to make the best use of storage
Uses change feed processor to read from the source collection
Uses bulk executor to write to the target collection

A continous web job that run in all instances in a web app and this is responsible for reading the change feed using change feed processor and writing to destination using bulk executor
A single instance web job that is responsible for monitoring the migration
A web nodejs app for the frontend that takes inputs to start the migration
The comunication between the web app and the web jobs happens through a cosmosdb database and webjobs poll for any changes in the db to start the migration

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