Re-use MongoDB MongoClient in ASP.NET-Core service

Question

So I'm building an ASP.NET-Core API connecting to a mongoDB instance. I was reading through the official Microsoft tutorial regarding this topic and came across the linked code sample.

Basically they instantiate a BookService and create a new instance of MongoClient in the scope of the constructor.

private readonly IMongoCollection<Book> _books;

public BookService(IBookstoreDatabaseSettings settings)
{
    var client = new MongoClient(settings.ConnectionString);
    var database = client.GetDatabase(settings.DatabaseName);
    _books = database.GetCollection<Book>(settings.BooksCollectionName);
}

As I understand this the _books collection would still work without the MongoClient instance present since it knows which collection it's assigned to and how to communicate with it BUT the mongoDB MongoClient re-use guidelines suggests to store a global/static instance of the client to re-use. (I guess for the same port-exhaustion, etc. reason you would want to re-use HTTPClients? Also it supports internal connection pooling, which is nice!)

Thinking further on what they imply I was quite sure it would be a bad idea to instantiate and immediately drop an instance for a client for each of my services. But I dont't know anything about MongoDB on this scope.

I know it's just a tutorial and they tend to be the "quick and dirty" way of coding but since I'm new to this whole topic I just wanted to make sure I would start out properly.

So is it OK doing it the "Microsoft way" or should I just create a global instance for the client or a factory altogether?

//Edit:

For clarification: Would it be better to register the MongoClient as a Singleton on Startup and inject it into classes that need it OR use the method described above?

Answer 1

This is how I typically add Mongo to my pipelines:

services.AddSingleton<IMongoClient>(sp =>
{ 
    var connectionString = "";
    return new MongoClient(connectionString);
});
services.AddScoped(sp =>
{
    var client = sp.GetRequiredService<IMongoClient>();
    var database = "";
    return client.GetDatabase(database);
});

This gives me a scoped IDatabase instance I can inject anywhere I need it (while using just one singleton IMongoClient instance).