I have a Web Api project which relies heavily on Azure Cosmos DB. Until now, having one Cosmos DB account (one connection string) was sufficient. Now a new requirement is to be able to connect to a different Cosmos (two connection strings) depending on an incoming parameter.
For customerId X we should fetch documents from Cosmos DB 1 and for another customer Y we have to look in Cosmos DB 2.
Until now my Startup.cs file registered a singleton instance of CosmosClient. Which in turn gets instantiated like this cosmosClient = new CosmosClient(endpointUrl, primaryKey); And this worked really well. The Web Api was easily able to process all requests. But now that we have to new up a CosmosClient per request, performance is really bad.
So my question is; Is there a way to have multiple instances of the same singleton? As in; can we create a single instance of the combination Class+EndPointUrl? (Would that still be a singleton?)
Right now, we are newing up thousands of CosmosClients every minute. And we really need just one more compared to what we had earlier.
There's multiple ways to do this, but an easy implementation would be to create a wrapper around each CosmosClient you use. The only use of the wrapper will be to allow you to use various instances of the CosmosClient and differentiate them by their types.
//Create your own class for each client inheriting the behaviour of CosmosClient
public class ContosoCosmosClient : CosmosClient
{
public ContosoCosmosClient(string connectionString, CosmosClientOptions clientOptions = null) : base(connectionString, clientOptions)
{
}
public ContosoCosmosClient(string accountEndpoint, string authKeyOrResourceToken, CosmosClientOptions clientOptions = null) : base(accountEndpoint, authKeyOrResourceToken, clientOptions)
{
}
public ContosoCosmosClient(string accountEndpoint, TokenCredential tokenCredential, CosmosClientOptions clientOptions = null) : base(accountEndpoint, tokenCredential, clientOptions)
{
}
}
//In Startup.up add a Singleton for each client
services.AddSingleton(new ContosoCosmosClient(...));
services.AddSingleton(new FabrikamCosmosClient(...));
Then in your business logic you can add both clients and depending on your logic choose which client you want to use:
public class MyService
{
public MyService(ContosoCosmosClient contosoClient, FabrikamCosmosClient fabrikamClient)
{
//...
}
}
Thanks for all comments and answers.
In the end, is this case, the best solution was the approach that was suggested by Mr. T. https://devblogs.microsoft.com/cosmosdb/httpclientfactory-cosmos-db-net-sdk/
I'm now still using one CosmosClient, Scoped. Which allows dynamic use of endpoints.
By injecting the IHttpClientFactory and setting the CosmosClientOptions like this;
{
HttpClientFactory = () => _httpClientFactory.CreateClient("cosmos")
});
we are now making full use of the HttpClient and its ability to reuse ports.