Category: Redis Cache

Load Balancing in Azure PaaS and Redis Cache

by Chun Lin, posted in Cloud Computing: Microsoft Azure, Experience, Load Balancing, Redis Cache

Azure Load Balancer

In Azure PaaS, Cloud Service automatically includes the Azure Load Balancer in front of web role instances for external endpoints. Hence, it allows scaling and when we specify more than one instance in web role, the Azure Load Balancer is responsible for routing incoming traffic to role instances.

When a role instance is brought online by Windows Azure, the OnStart method will be called and the role instance will be marked as Busy. Azure Load Balancer thus will not direct traffic to the role instance. Hence, having more than one role instance actually help on keeping the website accessible while deploying new code to the site.

Azure Load Balancer 5-Tuple Hash
Azure Load Balancer 5-Tuple Hash

Azure Load Balancer does not use Sticky Session. The distribution algorithm used by the balancer is 5 Tuple (Source IP, Source Port, Destination IP, Destination Port, and Protocol Type) Hash to map traffic to available instances. Hence, connections initiated from the same client computer cannot be guaranteed to always reach the same instance. Hence, it is important to build a fully stateless web application.

Where to Store ASP .NET Session State?

If we are going to use load balancing in our ASP .NET web applications, Session State can no longer be kept in memory of an instance. Instead, the Sessions need to be stored in SQL Server or State Server. Those are the three popular Session-State Modes available, i.e. InProc, SQLServer, and StateServer.

Now, with Azure Redis Cache, we can use the 4th option, the Custom mode, to store Session State values.

First of all, we need to download RedisSessionStateProvider from Nuget so that all necessary assembly references will be added automatically to our web application project. In addition, there will be new lines added to web.config, as shown below, to help us get started with Redis Cache Session State Provider.

<sessionState mode="Custom" customProvider="MySessionStateStore">
    <providers>
        <!--
            <add name="MySessionStateStore" 
            host = "127.0.0.1" [String]
            port = "" [number]
            accessKey = "" [String]
            ssl = "false" [true|false]
            throwOnError = "true" [true|false]
            retryTimeoutInMilliseconds = "0" [number]
            databaseId = "0" [number]
            applicationName = "" [String]
            connectionTimeoutInMilliseconds = "5000" [number]
            operationTimeoutInMilliseconds = "5000" [number]
            />
        -->
        <add name="MySessionStateStore" type="Microsoft.Web.Redis.RedisSessionStateProvider" host="127.0.0.1" accessKey="" ssl="false" />
    </providers>
</sessionState>

As shown in the commented section, we need to provide values to a few attributes before we can use the Redis Cache. Those values can be easily found on the new Azure Preview Portal. So, a complete configuration should be as follows.

<add name="MySessionStateStore" 
type="Microsoft.Web.Redis.RedisSessionStateProvider"
host="contoso5.redis.cache.windows.net"
accessKey="..." 
ssl="true" 
/>

Yup, that’s all. We can now happily use Redis Cache Session State Provider to make Session variables works well with the load balancing in our web applications. =)

For more information about Redis Cache Session State Provider, please read its documentation.

Summer 2015 Self-Learning Project

This article is part of my Self-Learning in this summer. To read the other topics in this project, please click here to visit the project overview page.

Summer Self-Learning Banner

Summer 2015 Self-Learning

by Chun Lin, posted in ASP.NET, Bootstrap, C#, Cloud Computing: Microsoft Azure, Code First, Entity Framework, Experience, Google Maps API, Google PageSpeed, HTML5, JavaScript, jQuery, Load Balancing, MVC 5, Razor, Redis Cache, Security, SQL, Website Performance

Summer Self-Learning
It has been about half a year since I started to learn ASP .NET MVC and Entity Framework (EF). In this period of time, I have learnt about not just MVC and EF, but also Azure PaaS, Google Maps API, web application security, cool jQuery plugins, Visual Studio Online, etc.

In the beginning of May, I started to note down useful things I’d learned in my learning journey. Months of bringing together information in this summer has helped me compile my notes about what I’ve learned in the past 6 months. I have currently completed compiling notes for 17 topics that I’ve learnt in this summer.

I listed down the title of the 17 posts below to give you a quick overview about all the 17 topics.

Contents

ASP .NET MVC and Entity Framework

Security

Microsoft Azure

Google APIs

Web Development Tools

Learning After Work

I’m working in Changi Airport. The office working hour is from 8:30am to 6pm. In addition, I am staying quite far from the airport which will take about one hour for me to travel from home to office. Hence, the only time that I can have sufficient time to work on personal projects is weekends.

This summer self-learning project is originally planned to be done by the end of May. Normally, it takes me about one day to finish writing a post. After that, if I find any new materials about the topics, I will then modify the post again. Sometimes, however, I am just too tired and I would not write anything even though it’s weekend. Hence, I end up finishing all the 17 topics three months later.

This summer learning project covers not only what I’ve learnt in my personal projects, but also new skills that I learn in my workplace. I always enjoy having a chat with my colleagues about the new .NET technology, app development, Azure hosting, and other interesting development tools. So yup, these 17 articles combine all the new knowledge I acquire.

I’m also very happy that that I am able to meet developers from both .NET Developers Community Singapore and Azure Community Singapore and share with them what I’ve learnt. That gives me a great opportunity to learn from those experienced .NET developers. =)

Azure Community March Meetup in Microsoft Singapore office.
Azure Community March Meetup in Microsoft Singapore office.

I am not that hardworking to work on personal projects every day. Sometimes, I will visit family and friends. Sometimes, I will travel with friends to overseas. Sometimes, I will play computer games or simply just sleep at home. So ya, this self-learning project takes a longer time to complete. =D

Working on personal projects after work is stressful also. Yup, so here is a music that helps reducing my stress. =)