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c#azure-functionsazure-cosmosdb
CamHart
CamHart

Reputation: 4335

How do DocumentDBAttribute bindings respond to throttling?

I have azure functions (C# v1 functions--non scripted) that use DocumentDBAttribute bindings for both reading and writing documents. How do those bindings respond to throttling in the following situations?

This is for functions v1.

First case:

        //input binding
        [DocumentDB(ResourceNames.APCosmosDBName, 
          ResourceNames.EpisodeOfCareCollectionName,
          ConnectionStringSetting = "APCosmosDB",
          CreateIfNotExists = true)] ICollector<EOC> eoc,
        //...
        eoc.Add(new EOC()); //what happens here if throttling is occuring?

Second case:

[DocumentDB(ResourceNames.ORHCasesDBName, ResourceNames.ORHCasesCollectionName, ConnectionStringSetting = "ORHCosmosDBCases", CreateIfNotExists = true, Id = "{id}")] string closedCaseStr,

Upvotes: 1

Views: 70

Answers (1)

Mikhail Shilkov
Mikhail Shilkov

Reputation: 35134

Both input and output bindings use CosmosDB SDK which has the retry mechanism in place.

By default, SDK retries 9 times on a throttled result, after that, the exception is bubbled and you Function will error. Depending on the trigger type, it will fail HTTP call, put the message back to the queue etc.

The retries respect the timing recommendation returned by Cosmos DB:

When a client is sending requests faster than the allowed rate, the service will return HttpStatusCode 429 (Too Many Request) to rate limit the client. The current implementation in the SDK will then wait for the amount of time the service tells it to wait and retry after the time has elapsed.

At the moment, there is no way to configure the bindings with a policy other than default.

Upvotes: 6

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