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Database Notes

All data is held in a single MongoDB database called smilrDb across two collections events and feedback. If they don't exist, the database and collections will be created by the data API on first access, so there is no need to initialize the database.
The app has been developed and tested again MongoDB versions 3.6 and 3.4, however only very standard Mongo API functionality is used, so it is expected that other 3.x versions will be compatible.

The choice of MongoDB allows us to explore several deployment architectures, the main two being

  • Running MongoDB as a containerised microservice
  • Using cloud platform service, namely Azure Cosmos DB

Switching between the two options is simply a matter of changing the MongoDB connection string used by the data API (MONGO_CONNSTR), this can be done to highlight or demonstrate the compatibility of Cosmos DB

Collection Sharding

The data-access layer supports sharded collections, but sharding is not mandatory. The shard keys for the collections are as follows:

  • events collection to be set with a shard key of type
  • feedback collection to be set with a shard key of event

Option 1 - MongoDB as a containerised microservice

If you don't want to use platform services or have any external dependencies, then running MongoDB in a container along side our two other microservices is an option. This represents a more "pure microservices" scenario

The provided Azure Templates and Kubernetes configurations and docs provide examples of this scenario

Option 2 - Using Azure Cosmos DB

As Azure Cosmos DB fully supports the MonogDB API, you can use Cosmos DB to deploy Smilr. This provides a number of benefits, such as near global scale, geo-replication and a range of consistency models. Deployment of a new Cosmos DB account is simple, using the Azure CLI it is a single command. Note the account name must be globally unique so you will have to change it

az cosmosdb create --resource-group {res_group} --name {change_me} --kind MongoDB

You can then obtain the MongoDB connection string using the Azure portal or the following command:

az cosmosdb list-connection-strings --resource-group {res_group} --name {change_me}

Option 3 - Run MongoDB Locally

You have three options when it comes to running MongoDB locally:

Use Windows Subsystem For Linux (WSL) - Ubuntu

Using Windows Subsystem For Linux (WSL) is probably the easiest way to run MongoDB on a Windows 10 machine. If you haven't already enabled WSL and installed a Linux distribution, then do so. I strongly recommend picking Ubuntu as the distribution to run.

Open an Ubuntu bash terminal and install MonogDB with the following:

sudo apt update
sudo apt install -y mongodb
sudo mkdir /data/db

Then start the server with:

sudo mongod

MonogDB server will start and be listening on all IPs by default, there is no authentication or SSL so you can simply connect with mongodb://localhost as the connection string

Loading Demo Data

The database requires no initialization, however a helper script is provided to populate the system with a set of simple demo data:

curl -L https://raw.github.com/benc-uk/smilr/master/etc/bash/loadData.sh | sh

The demo data held in demodata.json