CODEWITHSUNDEEP
asp.net-coreazure-cosmosdb
Joe Herres
Joe Herres

Reputation: 11

Asp.net core 3 application slow to load cosmos db query

I have a very simple Cosmos DB query that I am making from an asp.net core 3 Razor Pages application. The same query I make in Data Explorer in Azure will return results in 0.02ms. When I run it through the application, setting up stopwatches to see the duration of the calls, it can be anywhere from 400ms to 2000ms.

QueryDefinition queryDefinition = new QueryDefinition("SELECT * FROM Cache where Cache.JoinCode = @jc").WithParameter("@jc", JoinCode);

var query = _container.GetItemQueryIterator<HostCache>(queryDefinition);
List<HostCache> results = new List<HostCache>();
while (query.HasMoreResults)
{
    var response = await query.ReadNextAsync();
    results.AddRange(response.ToList());
}
return results.FirstOrDefault();

The long running request is the await query.ReadNextAsync();. Is there anything I can do to speed that up? Maybe I'm doing it wrong?

Upvotes: 0

Views: 1905

Answers (1)

Gaurav Mantri
Gaurav Mantri

Reputation: 136226

First, I would highly recommend that you (or anyone using Cosmos DB .Net SDK) to watch this video on Cosmos DB Youtube Channel: https://www.youtube.com/watch?v=McZIQhZpvew. This provides really useful information about the best practices to follow when working with this SDK.

This video will explain why the first request takes so much time and how you can speed that up.

To summarize for the purpose of this answer, creating an instance of Cosmos Client (with "Direct" connection mode) does not do much. When you make the 1st request with that client, the initialization happens and at that time SDK makes a few network requests to get necessary information about establishing "Direct" (TCP) connection. That's why it takes a great deal of time with the 1st request. After the 1st request, the information is cached by the SDK so subsequent requests take much less time than the 1st one.

To do the initialization while creating Cosmos client, you would need to use CreateAndInitializeAsync method of the CosmosClient. Here's an example of the same from the documentation page:

    using Microsoft.Azure.Cosmos;
    List<(string, string)> containersToInitialize = new List<(string, string)>
    { ("DatabaseName1", "ContainerName1"), ("DatabaseName2", "ContainerName2") };
    
    CosmosClient cosmosClient = await CosmosClient.CreateAndInitializeAsync("connection-string-from-portal",
containersToInitialize)

Upvotes: 6

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