Skip to main content

What to do when you hit the throughput limits of Azure Storage (Blobs)

In this post we will talk about how we can detect when we hit a throughput limit of Azure Storage and what we can do in that moment.

Context
If we take a look on Scalability Targets of Azure Storage (https://azure.microsoft.com/en-us/documentation/articles/storage-scalability-targets/) we will observe that the limits are prety high. But, based on our business logic we can end up at this limits.
If you create a system that is hitted by a high number of device, you can hit easily the total number of requests rate that can be done on a Storage Account. This limits on Azure is 20.000 IOPS (entities or messages per second) where (and this is very important) the size of the request is 1KB.
Normally, if you make a load tests where 20.000 clients will hit different blobs storages from the same Azure Storage Account, this limits can be reached.

How we can detect this problem?
From client, we can detect that this limits was reached based on the HTTP error code that is returned by HTTP request.
There two errors code that we should take into account:

  • 503 - Service Unavailable (ServerBusy): The server is currently unable to receive requests. Please retry your request
  • 500 - Internal Server Error (OperationTimedOut): The operation could not be completed within the permitted time
In general we should get 503 HTTP error code for this case, but in both cases I would consider that I might hitted a limits.

What we can do?
Based on our business logic, there are different solutions for our problems. Let's cover a few scenarios.


Problem 1: During multiple uploads in blobs on the same Azure Storage Account we hit a limits
In this case we are trying from multiple clients to upload content to the same Azure Storage Account

Solution 1: Retry later
The most simple solution, because you don't know exactly what is the problem, is to wait for a specific time period and retry. It is important to not have the same time period used by all clients. 
This can be handled easily if each client generates a random retry time (between two ranges). 


Solution 2: Request another upload storage location 
The second solution will need to involve the backend. When a 500 or 503 error code is returned, the client could retry 2-3 times to see if the upload can be done. If we still receive this error after multiple retries we should go to the backend and request another location where we can upload content. The backed should have multiple storage accounts and assign another location where we should retry the upload.


Solution 3: Assign upload location from multiple Storage Accounts
When clients request a storage location for upload, the backend should manage multiple storage account and play the role of balancer. Assign and use different Storage Accounts for different upload requests.


Solution 4: Provide two or more upload locations to clients
When clients receive an upload location, they should receive more than one upload storage location. If we encounter issues with the first location, the second one should be used and so on. Similar with Storage Account and Primary and Secondary location.



Problem 2: During download of a blob storage content we hit a limit
In this case we have multiple clients that are trying to download content from the same Azure Storage Account.

Solution 1: Replicate content on multiple Storage Accounts and share the location in Round Robin manner
First of all we should replicate the content in multiple Storage Accounts. Once this is done, each time when a client request a storage location we should provide a location from a different Storage Account. In this way we should be able to distribute the load on multiple Storage Accounts.


Solution 2: Replicate content on multiple Storage Accounts and provide a list of download location
It is similar with previous solution. The only thing that is different is that each client receives multiple locations from where we can download the content. If we receive errors when download is made from the first location, he should try to use the second, the third one and so on.


Solution 3: Request another download location from backend
In this case, the backed has multiple locations where content is replicated. Each client receives one location from where we can download content. If there are kind of errors after multiple retries for the same location, he will request from the backend another download location .


Of course all this solutions can be combined. I recommend to start with the simplest one and add more logic when you need it. All the time, you should send (or prepare to send) a second location that can be used for Upload or Download.

Comments

Popular posts from this blog

How to check in AngularJS if a service was register or not

There are cases when you need to check in a service or a controller was register in AngularJS.
For example a valid use case is when you have the same implementation running on multiple application. In this case, you may want to intercept the HTTP provider and add a custom step there. This step don’t needs to run on all the application, only in the one where the service exist and register.
A solution for this case would be to have a flag in the configuration that specify this. In the core you would have an IF that would check the value of this flag.
Another solution is to check if a specific service was register in AngularJS or not. If the service was register that you would execute your own logic.
To check if a service was register or not in AngularJS container you need to call the ‘has’ method of ‘inhector’. It will return TRUE if the service was register.
if ($injector.has('httpInterceptorService')) { $httpProvider.interceptors.push('httpInterceptorService&#…

ADO.NET provider with invariant name 'System.Data.SqlClient' could not be loaded

Today blog post will be started with the following error when running DB tests on the CI machine:
threw exception: System.InvalidOperationException: The Entity Framework provider type 'System.Data.Entity.SqlServer.SqlProviderServices, EntityFramework.SqlServer' registered in the application config file for the ADO.NET provider with invariant name 'System.Data.SqlClient' could not be loaded. Make sure that the assembly-qualified name is used and that the assembly is available to the running application. See http://go.microsoft.com/fwlink/?LinkId=260882 for more information. at System.Data.Entity.Infrastructure.DependencyResolution.ProviderServicesFactory.GetInstance(String providerTypeName, String providerInvariantName) This error happened only on the Continuous Integration machine. On the devs machines, everything has fine. The classic problem – on my machine it’s working. The CI has the following configuration:

TeamCity.NET 4.51EF 6.0.2VS2013
It seems that there …

[Post-Event] Codecamp Conference Cluj-Napoca - Nov 19, 2016

Last day I was invited to another Codecamp Conference, that took place in Cluj-Napoca. Like other Codecamp Conferences, the event was very big, with more than 1.000 participants and 70 sessions. There were 10 tracks in parallel, so it was pretty hard to decide at  what session you want to join.
It was great to join this conference and I hope that you discovered something new during the conference.
At this event I talked about Azure IoT Hub and how we can use it to connect devices from the field. I had a lot of demos using Raspberry PI 3 and Simplelink SensorTag. Most of the samples were written in C++ and Node.JS and people were impressed that even if we are using Microsoft technologies, we are not limited to C# and .NET. World and Microsoft are changing so fast. Just looking and Azure IoT Hub and new features that were launched and I'm pressed (Jobs, Methods, Device Twin).
On backend my demos covered Stream Analytics, Event Hub, Azure Object Storage and DocumentDB.

Title:
What abo…