Performance analysis

Performance is the amount of work completed in a defined period of time and with a set of defined resources. It can be analyzed using one or more metrics that depend on the performance goal. The goal can be low latency, low memory footprint, reduced processor usage, or even reduced power consumption.

The act of performance analysis is also called profiling. Profiling is very important for making optimized applications and is achieved by instrumenting either the source or the instance of the application. By instrumenting the source, developers can spot common performance weak spots. By instrumenting an application instance, they can test the application on different environments. This type of instrumentation can also be known by the name benchmarking.

Node.js is known for being fast. Actually, it's not that fast; it's just as fast as your resources allow it. What Node.js is best at is not blocking your application because of an I/O task. The perception of performance can be misleading in Node.js applications. In some other languages, when an application task gets blocked—for example, by a disk operation—all other tasks can be affected. In the case of Node.js, this doesn't happen—usually.

Some people look at the platform as being single threaded, which isn't true. Your code runs on a thread, but there are a few more threads responsible for I/O operations. Since these operations are extremely slow compared to the processor's performance, they run on a separate thread and signal the platform when they have information for your application. Applications blocking I/O operations perform poorly. Since Node.js doesn't block I/O unless you want it to, other operations can be performed while waiting for I/O. This greatly improves performance.

V8 is an open source Google project and is the JavaScript engine behind Node.js. It's responsible for compiling and executing JavaScript, as well as managing your application's memory needs. It is designed with performance in mind. V8 follows several design principles to improve language performance. The engine has a profiler and one of the best and fast garbage collectors that exist, which is one of the keys to its performance. It also does not compile the language into byte code; it compiles it directly into machine code on the first execution.

A good background in the development environment will greatly increase the chances of success in developing high-performance applications. It's very important to know how dereferencing works, or why your variables should avoid switching types. Here are other useful tips you would want to follow. You can use a style guide like JSCS and a linter like JSHint to enforce them to for yourself and your team. Here are some of them:

Write small functions, as they're more easily optimized
Use monomorphic parameters and variables
Prefer arrays to manipulate data, as integer-indexed elements are faster
Try to have small objects and avoid long prototype chains
Avoid cloning objects because big objects will slow the operations

Monitoring

After an application is put into production mode, performance analysis becomes even more important, as users will be more demanding than you were. Users don't accept anything that takes more than a second, and monitoring the application's behavior over time and over some specific loads will be extremely important, as it will point to you where your platform is failing or will fail next.

Yes, your application may fail, and the best you can do is be prepared. Create a backup plan, have fallback hardware, and create service probes. Essentially, anticipate all the scenarios you can think of, and remember that your application will still fail. Here are some of those scenarios and aspects that you should monitor:

When in production, application usage is of extreme importance to understand where your application is heading in terms of data size or memory usage. It's important that you carefully define source code probes to monitor metrics—not only performance metrics, such as requests per second or concurrent requests, but also error rate and exception percentage per request served. Your application emits errors and sometimes throws exceptions; it's normal and you shouldn't ignore them.
Don't forget the rest of the infrastructure. If your application must perform at high standards, your infrastructure should too. Your server power supply should be uninterruptible and stable, as instability will degrade your hardware faster than it should.
Choose your disks wisely, as faster disks are more expensive and usually come in smaller storage sizes. Sometimes, however, this is actually not a bad decision when your application doesn't need that much storage and speed is considered more important. But don't just look at the gigabytes per dollar. Sometimes, it's more important to look at the gigabits per second per dollar.
Also, your server temperature and server room should be monitored. High temperatures degrades performance and your hardware has an operation temperature limit. Security, both physical and virtual, is also very important. Everything counts for the standards of high performance, as an application that stops serving its users is not performing at all.

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Node.js High Performance

By : Resende

Node.js High Performance

By: Resende

Overview of this book

Performance analysis

Monitoring

Node.js High Performance

By : Resende

Node.js High Performance

By: Resende

Overview of this book

Performance analysis

Monitoring

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