ASP.NET Core 1.0 High Performance

Chapter 1. Why Performance Is a Feature

This is an exciting time to be a C# developer. Microsoft is in the middle of one of the biggest changes in its history, and it is embracing open source software. The ASP.NET and .NET frameworks are being rebuilt from the ground up to be componentized, cross-platform, and open source.

ASP.NET Core 1.0 and .NET Core 1.0 (previously called ASP.NET 5 and .NET Core 5) embrace many ideas from popular open source projects, such as Go's ability to produce a statically-linked, standalone binary. You can now compile a single native executable that is free of any external dependencies and run it on a system without .NET installed.

The ASP.NET Model View Controller (MVC) web application framework, which is now part of ASP.NET Core 1.0, borrows heavily from Ruby on Rails and Microsoft is keen in promoting tools, such as Node.js, Grunt, gulp, and Yeoman. There is also TypeScript, which is a statically-typed version of JavaScript that was developed at Microsoft.

By reading this book, you will learn how to write high-performance software using these new .NET Core technologies. You'll be able to make your web applications responsive to input and scalable to demand.

We'll focus on the latest Core versions of .NET. Yet, many of these techniques also apply to previous versions, and they will be useful for web application development in general (in any language or framework).

Understanding how all of these new frameworks and libraries fit together can be a bit confusing. We'll present the various available options while still using the newest technology, guiding you down the path to high-speed success, and avoiding performance pitfalls.

After finishing this book, you will understand what problems can occur when web applications are deployed at scale (to distributed infrastructure) and know how to avoid or mitigate these issues. You will gain the experience of how to write high-performance applications without learning about issues the hard way.

In this chapter, we will cover the following topics.

Performance as a feature
The common classes of performance issues
Basic hardware knowledge
Microsoft tools and alternatives
New .NET naming and compatibility

Performance as a feature

You may have previously heard about the practice of treating performance as a first-class feature. Traditionally, performance (along with things such as security, availability and uptime) was only considered a Non-Functional Requirement (NFR) and usually had some arbitrary made-up metrics that needed to be fulfilled. You may have heard the term "performant" before. This is the quality of performing well and, often, is captured in requirements without quantification, providing very little value. It is better to avoid this sort of corporate jargon when corresponding with clients or users.

Using the outdated waterfall method of development, these NFRs were inevitably left until the end, and dropped from an over-budget and late project in order to get the functional requirements completed. This resulted in a substandard product that was unreliable, slow, and often insecure (as reliability and security are also often neglected NFRs). Think about how many times you're frustrated at software that lags behind in responding to your input. Perhaps, you used a ticket-vending machine or a self-service checkout that is unresponsive to the point of being unusable.

There is a better way. By treating performance as a feature and considering it at every stage of your agile development process, you can get users and customers to love your product. When software responds quicker than a user can perceive, it is a delight to use, and this doesn't slow them down. When there is noticeable lag, then users need to adjust their behavior to wait for the machine instead of working at their own pace.

Computers have incredible amounts of processing power today, and they now possess many more resources than they did even just a few years ago. So, why do we still have software that is noticeably slow at responding, when computers are so fast and can calculate much quicker than people can? The answer to this is poorly written software that does not consider performance. Why does this happen? The reason is that often the signs of poor performance are not visible in development, and they only appear when deployed. However, if you know what to look for, then you can avoid these problems before releasing your software to the production environment.

This book will show you how to write software that is a joy to use and never keeps the user waiting or uninformed. You will learn how to make products that users will love instead of products that frustrate them all the time.

Common classes of performance problems

Let's take a look at some common areas of performance problems and see whether they matter or not. We will also learn why we often miss these issues during development.

Language considerations

People often focus on the speed of the programming language that is used. However, this often misses the point. This is a very simplistic view that glosses over the nuances of technology choices. It is easy to write slow software in any language.

With the huge amounts of processing speed that is available today, relatively "slow" interpreted languages can often be fast enough, and the increase in development speed is worth it. It is important to understand the arguments and the trade-offs involved even if by reading this book you have already decided to use C# and .NET.

The way to write the fastest software is to get down to the metal and write in assembler (or even machine code). This is extremely time consuming, requires expert knowledge, and ties you to a particular processor architecture and instruction set; therefore, we rarely do this these days. If this happens, then it's only done for very niche applications (such as virtual reality games, scientific data crunching, and sometimes embedded devices) and usually only for a tiny part of the software.

The next level of abstraction up is writing in a language, such as Go, C, or C++, and compiling the code to run on the machine. This is still popular for games and other performance-sensitive applications, but you often have to manage your own memory (which can cause memory leaks or security issues, such as buffer overflows).

A level above is software that compiles to an intermediate language or byte code and runs on a virtual machine. Examples of this are Java, Scala, Clojure, and, of course, C#. Memory management is normally taken care of, and there is usually a Garbage Collector (GC) to tidy up unused references (Go also has a GC). These applications can run on multiple platforms, and they are safer. However, you can still get near to native performance in terms of execution speed.

Above these are interpreted languages, such as Ruby, Python, and JavaScript. These languages are not usually compiled, and they are run line-by-line by an interpreter. They usually run slower than a compiled language, but this is often not a problem. A more serious concern is catching bugs when using dynamic typing. You won't be able to see an error until you encounter it, whereas many errors can be caught at compile time when using statically-typed languages.

It is best to avoid generic advice. You may hear an argument against using Ruby on Rails, citing the example of Twitter having to migrate to Java for performance reasons. This may well not be a problem for your application, and indeed having the popularity of Twitter would be a nice problem to have. A bigger concern when running Rails may be the large memory footprint, making it expensive to run on cloud instances.

This section is only to give you a taste, and the main lesson is that normally, language doesn't matter. It is not usually the language that makes a program slow, it's poor design choices. C# offers a nice balance between speed and flexibility that makes it suitable for a wide range of applications, especially server-side web applications.

Types of performance problems

There are many types of performance problems, and most of them are independent of the programming language that is used. A lot of these result from how the code runs on the computer, and we will cover the impact of this later on in the chapter.

We will briefly introduce common performance problems here and will cover them in more detail in later chapters of this book. Issues that you may encounter will usually fall into a few simple categories, including the following:

Latency:
- Memory latency
- Network latency
- Disk and I/O latency
- Chattiness / handshakes
Bandwidth:
- Excessive payloads
- Unoptimized data
- Compression
Computation:
- Working on too much data
- Calculating unnecessary results
- Brute forcing algorithms
Doing work in the wrong place:
- Synchronous operations that could be done offline
- Caching and coping with stale data

When writing software for a platform, you are usually constrained by two resources. These are the computation processing speed and accessing remote (to the processor) resources.

Processing speed is rarely a limiting factor these days, and this could be traded for other resources, for example, compressing some data to reduce the network transfer time.

Accessing remote resources, such as main memory, disk, and the network will have various time costs. It is important to understand that speed is not a single value, and it has multiple parameters. The most important of these are bandwidth and, crucially, latency.

Latency is the lag in time before the operation starts, whereas bandwidth is the rate at which data is transferred once the operation starts. Posting a hard drive has a very high bandwidth, but it also has very high latency. This would make it very slow to send lots of text files back and forth, but perhaps, this is a good choice to send a large batch of 3D videos (depending on the Weissman score). A mobile phone data connection may be better for the text files.

Although this is a contrived example, the same concerns are applicable to every layer of the computing stack often with similar orders of magnitude in time difference. The problem is that the differences are too quick to perceive, and we need to use tools and science to see them.

The secret to solving performance problems is in gaining a deeper understanding of the technology and knowing what happens at the lower levels. You should appreciate what the framework is doing with your instructions at the network level. It's also important to have a basic grasp of how these commands run on the underlying hardware, and how they are affected by the infrastructure that they are deployed to.

When performance matters

Performance is not always important in every situation. Learning when performance does and doesn't matter is an important skill to acquire. A general rule of thumb is that if the user has to wait for something to happen, then it should perform well. If this is something that can be performed asynchronously, then the constraints are not as strict, unless an operation is so slow that it takes longer than the time window for it; for example, an overnight batch job on an old financial services mainframe.

A good example from a web application standpoint is rendering user view versus sending e-mail. It is a common, yet naïve, practice to accept a form submission and send an e-mail (or worse, many e-mails) before returning the result. Yet, unlike a database update, an e-mail is not something that happens almost instantly. There are many stages over which we have no control that will delay an e-mail in reaching a user. Therefore, there is no need to send an e-mail before returning the result of the form. You can do this offline and asynchronously after the result of the form submission is returned.

The important thing to remember here is that it is the perception of performance that matters and not absolute performance. It can be better to not do some work (or at least defer it) rather than speed it up.

This may be counterintuitive, especially considering how individual computer operations can be too quick to perceive. However, the multiplying factor is scale. One operation may be relatively quick, but millions of them may accumulate to a visible delay. Optimizing these will have a corresponding effect due to the magnification. Improving code that runs in a tight loop or for every user is better than fixing a routine that runs only once a day.

Slower is sometimes better

In some situations, processes are designed to be slow, and this is essential to their operation and security. A good example of this, which may be hit in profiling, is password hashing or key stretching. A secure password hashing function should be slow so that the password, which (despite being bad practice) may have been reused on other services, is not easily recovered.

We should not use generic hashing functions, such as MD5, SHA1, and SHA256, to hash passwords because they are too quick. Some better algorithms that are designed for this task are PBKDF2 and bcrypt, or even Argon2 for new projects. Always remember to use a unique salt per password too. We won't go into any more details here, but you can clearly see that speeding up password hashing would be bad, and it's important to identify where to apply optimizations.

Why issues are missed

One of the main reasons that performance issues are not noticed in development is that some problems are not perceivable on a development system. Issues may not occur until latency increases. This may be because a large amount of data was loaded into the system and retrieving a specific record takes longer. This may also be because each piece of the system is deployed to a separate server, increasing the network latency. When the number of users accessing a resource increases, then the latency will also increase.

For example, we can quickly insert a row into an empty database or retrieve a record from a small table, especially when the database is running on the same physical machine as the web server. When a web server is on one virtual machine and the big database server is on another, then the time taken for this operation can increase dramatically.

This will not be a problem for one single database operation, which appears just as quick to a user in both cases. However, if the software is poorly written and performs hundreds or even thousands of database operations per request, then this quickly becomes slow.

Scale this up to all the users that a web server deals with (and all of the web servers) and this can be a real problem. A developer may not notice that this problem exists if they're not looking for it, as the software performs well on their workstation. Tools can help in identifying these problems before the software is released.

Measuring

The most important takeaway from this book is the importance of measuring. You need to measure problems or you can't fix them. You won't even know when you have fixed them. Measurement is the key to fixing performance issues before they become noticeable. Slow operations can be identified early on, and then they can be fixed.

However, not all operations need optimizing. It's important to keep a sense of perspective, but you should understand where the chokepoints are and how they will behave when magnified by scale. We'll cover measuring and profiling in the next chapter.

The benefits of planning ahead

By considering performance from the very beginning, it is cheaper and quicker to fix issues. This is true for most problems in software development. The earlier you catch a bug, the better. The worst time to find a bug is once it is deployed and then being reported by your users.

Performance bugs are a little different when compared to functional bugs because often, they only reveal themselves at scale, and you won't notice them before a live deployment unless you go looking for them. You can write integration and load tests to check performance, which we will cover later in this book.

Understanding hardware

Remember that there is a computer in computer science. It is important to understand what your code runs on and the effects that this has, this isn't magic.

Storage access speeds

Computers are so fast that it can be difficult to understand which operation is a quick operation and which is a slow one. Everything appears instant. In fact, anything that happens in less than a few hundred milliseconds is imperceptible to humans. However, certain things are much faster than others are, and you only get performance issues at scale when millions of operations are performed in parallel.

There are various different resources that can be accessed by an application, and a selection of these are listed, as follows:

CPU caches and registers:
- L1 cache
- L2 cache
- L3 cache
RAM
Permanent storage:
- Local Solid State Drive (SSD)
- Local Hard Disk Drive (HDD)
Network resources:
- Local Area Network (LAN)
- Regional networking
- Global internetworking

Virtual Machines (VMs) and cloud infrastructure services could add more complications. The local disk that is mounted on a machine may in fact be a shared network disk and respond much slower than a real physical disk that is attached to the same machine. You may also have to contend with other users for resources.

In order to appreciate the differences in speed between the various forms of storage, consider the following graph. This shows the time taken to retrieve a small amount of data from a selection of storage mediums:

This graph has a logarithmic scale, which means that the differences are very large. The top of the graph represents one second or one billion nanoseconds. Sending a packet across the Atlantic Ocean and back takes roughly 150 milliseconds (ms) or 150 million nanoseconds (ns), and this is mainly limited by the speed of light. This is still far quicker than you can think about, and it will appear instantaneous. Indeed, it can often take longer to push a pixel to a screen than to get a packet to another continent.

The next largest bar is the time that it takes a physical HDD to move the read head into position to start reading data (10 ms). Mechanical devices are slow.

The next bar down is how long it takes to randomly read a small block of data from a local SSD, which is about 150 microseconds. These are based on Flash memory technology, and they are usually connected in the same way as a HDD.

The next value is the time taken to send a small datagram of 1 KB (1 kilobyte or 8 kilobits) over a gigabit LAN, which is just under 10 microseconds. This is typically how servers are connected in a data center. Note how the network itself is pretty quick. The thing that really matters is what you are connecting to at the other end. A network lookup to a value in memory on another machine can be much quicker than accessing a local drive (as this is a log graph, you can't just stack the bars).

This brings us on to main memory or RAM. This is fast (about 100 ns for a lookup), and this is where most of your program will run. However, this is not directly connected to the CPU, and it is slower than the on die caches. RAM can be large, often large enough to hold all of your working dataset. However, it is not as big as disks can be, and it is not permanent. It disappears when the power is lost.

The CPU itself will contain small caches for data that is currently being worked on, which can respond in less than 10 ns. Modern CPUs may have up to three or even four caches of increasing size and latency. The fastest (less than 1 ns to respond) is the Level 1 (L1) cache, but this is also usually the smallest. If you can fit your working data into these few MB or KB in caches, then you can process it very quickly.

Scaling approach changes

For many years, the speed and processing capacity of computers increased at an exponential rate. This was known as Moore's Law, named after Gordon Moore of Intel. Sadly, this era is no Moore (sorry). Single-core processor speeds have flattened out, and these days increases in processing ability come from scaling out to multiple cores, multiple CPUs, and multiple machines (both virtual and physical). Multithreaded programming is no longer exotic, it is essential. Otherwise, you cannot hope to go beyond the capacity of a single core. Modern CPUs typically have at least four cores (even for mobiles). Add in a technology such as hyper-threading, and you have at least eight logical CPUs to play with. Naïve programming will not be able to fully utilize these.

Traditionally, performance (and redundancy) was provided by improving the hardware. Everything ran on a single server or mainframe, and the solution was to use faster hardware and duplicate all components for reliability. This is known as vertical scaling, and it has reached the end of its life. It is very expensive to scale this way and impossible beyond a certain size. The future is in distributed-horizontal scaling using commodity hardware and cloud computing resources. This requires that we write software in a different manner than we did previously. Traditional software can't take advantage of this scaling like it can easily use the extra capabilities and speed of an upgraded computer processor.

There are many trade-offs that have to be made when considering performance, and it can sometimes feel like more of a black art than a science. However, taking a scientific approach and measuring results is essential. You will often have to balance memory usage against processing power, bandwidth against storage, and latency against throughput.

An example is deciding whether you should compress data on the server (including what algorithms and settings to use) or send it raw over the wire. This will depend on many factors, including the capacity of the network and the devices at both ends.

Tools and costs

Licensing of Microsoft products has historically been a minefield of complexity. You can even sit for an official exam on it and get a qualification. Microsoft's recent move toward open source practices is very encouraging, as the biggest benefit of open source is not the free monetary cost but that you don't have to think about the licensing costs. You can also fix issues, and with a permissive license (such as MIT), you don't have to worry about much. The time costs and cognitive load of working out licensing implications now and in the future can dwarf the financial sums involved (especially for a small company or startup).

Tools

Despite the new .NET framework being open source, many of the tools are not. Some editions of Visual Studio and SQL Server can be very expensive. With the new licensing practice of subscriptions, you will lose access if you stop paying, and you are required to sign in to develop. Previously, you could keep using existing versions licensed from a Microsoft Developer Network (MSDN) or BizSpark subscription after it expired and you didn't need to sign in.

With this in mind, we will try to stick to the free (community) editions of Visual Studio and the Express version of SQL Server unless there is a feature that is essential to the lesson, which we will highlight when it occurs. We will also use as many free and open source libraries, frameworks, and tools as possible.

There are many alternative options for lots of the tools and software that augments the ASP.NET ecosystem, and you don't just need to use the default Microsoft products. This is known as the ALT.NET (alternative .NET) movement, which embraces practices from the rest of the open source world.

Looking at some alternative tools

For version control, git is a very popular alternative to Team Foundation Server (TFS). This is integrated into many tools (including Visual Studio) and services, such as GitHub or GitLab. Mercurial (hg) is also an option. However, git has gained the most developer mindshare. Visual Studio Online offers both git and TFS integration.

PostgreSQL is a fantastic open source relational database, and it works with many Object Relational Mappers (O/RMs), including Entity Framework (EF) and NHibernate. Dapper is a great, and high-performance, alternative to EF and other bloated O/RMs. There are plenty of NoSQL options that are available too; for example, Redis and MongoDB.

Other code editors and Integrated Development Environments (IDEs) are available, such as Visual Studio Code by Microsoft, which also works on Apple Mac OS X. ASP.NET Core 1.0 (previously ASP.NET 5) runs on Linux (on Mono and CoreCLR). Therefore, you don't need Windows (although Nano Server may be worth investigating).

RabbitMQ is a brilliant open source message queuing server that is written in Erlang (which WhatsApp also uses). This is far better than Microsoft Message Queuing (MSMQ), which comes with Windows. Hosted services are readily available, for example, CloudAMQP.

The author has been a long time Mac user (since the PowerPC days), and he has run Linux servers since well before this. It's positive to see OS X become popular and to observe the rise of Linux on Android smartphones and cheap computers, such as the Raspberry Pi. You can run Windows 10 on a Raspberry Pi 2 and 3, but this is not a full operating system and only meant to run Internet of Things (IoT) devices. Having used Windows professionally for a long time, developing and deploying with Mac and Linux, and seeing what performance effects this brings is an interesting opportunity.

Although not open source (or always free), it is worth mentioning JetBrains products. TeamCity is a very good build and Continuous Integration (CI) server that has a free tier. ReSharper is an awesome plugin for Visual Studio, which will make you a better coder. They're also working on a C# IDE called Project Rider that promises to be good.

There is a product called Octopus Deploy, which is extremely useful for the deployment of .NET applications, and it has a free tier. Regarding cloud services, Amazon Web Services (AWS) is an obvious alternative to Azure, even if the AWS Windows support leaves something to be desired. There are many other hosts available, and dedicated servers can often be cheaper for a steady load if you don't need the dynamic scaling of the cloud.

Much of this is beyond the scope of this book, but you would be wise to investigate some of these tools. The point is that there is always a choice about how to build a system from the huge range of components available, especially with the new version of ASP.NET.

The new .NET

The new ASP.NET and the .NET Framework that it relies upon were rewritten to be open source and cross-platform. This work was called ASP.NET 5 while in development, but this has since been renamed to ASP.NET Core 1.0 to reflect that it's a new product with a stripped down set of features. Similarly, .NET Core 5 is now .NET Core 1.0, and Entity Framework 7 is now Entity Framework Core 1.0.

The web application framework that was called ASP.NET MVC has been merged into ASP.NET Core, although it's a package that can be added like any other dependency. The latest version of MVC is 6 and, along with Web API 2, this has been combined into a single product, called ASP.NET Core. MVC and Web API aren't normally referred to directly any more as they are simply NuGet packages that are used by ASP.NET Core. Not all features are available in the new Core frameworks yet, and the focus is on server-side web applications to start with.

All these different names can be perplexing, but naming things is hard. A variation of Phil Karlton's famous quote goes like this:

"There are only two hard things in Computer Science: cache invalidation, naming things, and off-by-one errors."

We've looked at naming here, and we'll get to caching later on in this book.

It can be a little confusing understanding how all of these versions fit together. This is best explained with a diagram like the following, which shows how the layers interact:

ASP.NET Core 1.0 can run against the existing .NET Framework 4.6 or the new .NET Core 1.0 framework. Similarly, .NET Core can run on Windows, Mac OS X, and Linux, but the old .NET only runs on Windows.

There is also the Mono framework, which has been omitted for clarity. This was a previous project that allowed .NET to run on multiple platforms. Mono was recently acquired by Microsoft, and it was open sourced (along with other Xamarin products). Therefore, you should be able to run ASP.NET Core using Mono on any supported operating system.

.NET Core focuses on web-application development and server-side frameworks. It is not as feature filled as the existing .NET Framework. If you write native-graphical desktop applications, perhaps using Windows Presentation Foundation (WPF), then you should stick with .NET 4.6.

As this book is mainly about web-application development, we will use the latest Core versions of all software. We will investigate the performance implications of various operating systems and architectures. This is particularly important if your deployment target is a computer, such as the Raspberry Pi, which uses a processor with an ARM architecture. It also has limited memory, which is important to consider when using a managed runtime that includes garbage collection, such as .NET.

Francisco Oct 10, 2016

Little specific information of .NET Core. It's more a general book.

Amazon Verified review

Amazon Customer Feb 18, 2017

I expected this to go deep into ASP.NET Core but book contains very general information about web applications and performance. Even worse all information is very shallow.

ASP.NET Core 1.0 High Performance: Create fast, scalable, and high performance applications with C#, ASP.NET Core 1.0, and MVC 6

What do you get with eBook?

ASP.NET Core 1.0 High Performance

Chapter 1. Why Performance Is a Feature

Performance as a feature

Common classes of performance problems

Language considerations