Skip to main content

Coding Stories - Optimize calls to Azure Table

This week I had the opportunity to make a code review for a startup. They decided to go on Azure from the first moment. The business logic that is behind the application is not very complex, but they are using pretty heavily Azure Storage, especially blobs and tables.
After a load tests, they observed that there are some performance problems on the storage side. The cause of this problem was not Azure. The code that was written didn't used Azure SDK properly.
Below you can find two causes of this problems.

CreateIfNotExists
This method is used when we don't know if a specific resource exists (like blobs or table).
CloudTable fooTable = tableClient.GetTableReference("foo");
foo.CreateIfNotExists();
…
There is not problem with this method as long as we don't have to many calls to it. Each time when we call it, a HTTPS request is send to Azure backend to check if that specific resource exists or not (if the resource doesn't exist, than it will be created automatically).
Normally, we could try to cache the instance of the CloudTable and reuse it as many times we can.
In their case this was not possible because each different client would have a dedicated table where he would add data. When you have 10 clients that are trying to access your system in the same time it is not a problem, but when you have 5.000 or 10.000 clients, than an additional REST call can impact your performance and increase the latency of your system.
In reality they don't need to check if the table exists each time. The table instance can be created in the moment when the user register into the system. Once the table is created, we don't need anymore to check if the table exist or not.
Don't forget that from the cost perspective it is the same thing if we have 1 table or 50.000 tables under an Azure Storage account. Costs and performance are not impacted.

Optimize Queries over Azure Table
Each user of the application is allowed to retrieve data from his own Azure Table. A simple filtering support would allow each user to filter data based on some simple rules.
CloudTable fooTable = tableClient.GetTableReference("fooTable");
TableQueuryDynamicTableEntity customQuery = new TableQueuryDynamicTableEntity()
  .Where(
    TableQuery.CombineFilters(
      TableQuery.GenerateFilterCondition("PartitionKey", QueryComparisons.Equal, "fooPartition"),
      TableOperators.And,
      TableQuery.CombineFilters(
        TableQuery.GenerateFilterCondition("RowKey", QueryComparisons.Equal, "rowKey1"),
        TableOperators.Or,
        TableQuery.GenerateFilterCondition("RowKey", QueryComparisons.Equal, "rowKey2"),
List<DynamicTableEntity> fooResults = fooTable.ExecuteQuery(customQuery).ToList();
In the above code two different queries are grouped together under the same query request. The problem with this query is that it will be executed over all the entities that are under the given table partition. Because of this, the performance of the request is very poor, even if we are making only one API call.
If we already know the partition and row key of the entity, there is no need to define a complex query that will scan all partitions.
Remarks: In Azure Table, each table has to have a partition key and a row key. The combination between this will form the unique key of the entity. For scalability and access speed optimization, Azure can slit a table based on partitions and store each partition in a different logical unit.
To make this code running faster, especially when the number of entities under a partition is high, is to make two different requests to Azure Table. Each request would add a different entity. Even if we are doing multiple requests, the overall performance will be much better.
TableOperation fooOperation1 = TableOperation.Retrive("fooPartition","rowKey1");
TableOperation fooOperation2 = TableOperation.Retrive("fooPartition","rowKey2");
DynamicTableEntity fooEntity1 = (Dynamic<TableEntity>) fooTable.Execute(fooOperation1).Result;
DynamicTableEntity fooEntity2 = (Dynamic<TableEntity>) fooTable.Execute(fooOperation2).Result;
Because the query that is executed over Azure Table is more simple - it doesn't need to search in all partition entities, the performance  will be very high.

Small things like this, can improve drastically the performance of our system. Before using a service or an SDK it is important to understand how it is working and what are the base principles.




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…