Pitfalls of AutoMapper

AutoMapper is a very popular .NET library for automatically mapping objects (e.g. database model to DTO). The mapping is done without having to write code to explicitly copy values over (except in cases where the mapping isn’t obvious, such as where property names don’t match or where transformations are necessary).

Surely, a library with over 144 million downloads on NuGet that lets you write less code is nothing but awesome, right? And yet, AutoMapper is one of four libraries that caused me nothing but grief, along with MediatR (by the same author), Entity Framework, and Fluent Validations.

When writing code, there are four main things I value:

  • Validity: the code does what it’s supposed to do without defects.
  • Performance: the code isn’t inefficient in ways that impact the application.
  • Maintainability: the code is easy to understand, reason about and debug. This point is entirely pragmatic, as opposed to the “clean code” camp that idolises code for its own sake.
  • Timeliness: the chosen approach should enable the solution to be delivered in a timely manner.

Thus, as I dissect AutoMapper in this article, I will do so in terms of these points.

Compile-Time vs Runtime

In my 2017 article “The Adapter Design Patterns for DTOs in C#“, I briefly mentioned AutoMapper and listed three reasons why I wasn’t a fan. The first of these was:

“The mapping occurs dynamically at runtime. Thus, as the DTOs evolve, you will potentially have runtime errors in production. I prefer to catch such issues at compile-time.”

The Adapter Design Patterns for DTOs in C#

For me, this is still one of the most important reasons to avoid AutoMapper. The whole point of using a statically typed language is that you can avoid costly runtime problems by catching errors at compile-time. Yet, using AutoMapper bypasses the compiler entirely, and compares objects dynamically at runtime.

This inevitably leads to bugs as the software evolves. Software Development Sucks‘ 2015 article “Why Automapping is bad for you” (hereinafter referred to as just “the SDS article”) has a very good example illustrating how simply renaming a property will cause the mapping to silently break (i.e. a field will go missing) without the compiler ever complaining.

Mapping as Logic

In recent years, declarative forms of programming have become a lot more popular, perhaps due to the growing influence of functional programming. In .NET libraries, this approach tends to manifest itself in the form of fluent syntax, which you can find in ASP .NET Core pipeline configuration, AutoMapper mapping configuration, and Fluent Validation among many other places.

However, mapping is actually logic, and you can’t treat it like declarative configuration. How do you debug it? How do you understand what it’s doing when complex object graphs are involved? That’s right, you can’t. Mapping needs to happen in code that you can reason about and debug, just like any other logic.

Also, teams that use AutoMapper normally end up with heaps of these declarative mapping rules, which defeats the purpose of not writing mapping code in the first place. While I can understand that there will be less properties to map manually, it’s not like it takes hours to write a few extra lines of code to map a few properties.

External Dependencies

The biggest problems I’ve seen with the use of AutoMapper relate to when certain properties are computed based on external dependencies, such as getting something from an API or database, or some expensive computation. To be fair, these problems are not intrinsic to AutoMapper at all, but they are still a valid part of this discussion.

Let’s say we have a UserId property that needs to be mapped to a full User (object) property in a destination object. This would require asynchronously requesting the User object from a database (or cache, or API, etc). However, the first obstacle we face is that AutoMapper doesn’t support async resolvers, and never will.

So how do we map something that requires an async call? Well, the first way I saw people do this is by running the async code synchronously, calling the .Result property. As I hope you’re aware, this is a terrible idea that can (and did) result in deadlocks (see “Common Mistakes in Asynchronous Programming with .NET“).

But there’s more to it than that. If you have any expensive call, async or otherwise, you should probably be doing it in batches rather than for each object you map (see “Avoid await in Foreach“), because it makes a huge difference in performance.

So, it’s actually a good thing that AutoMapper doesn’t support async mapping operations, because they shouldn’t be done as part of the DTO mapping at all, whether you’re using AutoMapper or doing it manually. It violates both the Single Responsibility Principle (mapping code doing more than just mapping) and Dependency Inversion (you’re hiding dependencies within your mapping code, possibly by using a Service Locator… how do you write unit tests for that?), and it also has very serious stability and performance consequences as mentioned above.


Libraries that do runtime magic like AutoMapper or inversion of control (IoC) containers use Reflection, which by its very nature is slow. While this is not likely to have an impact in most cases, and therefore we should not dismiss such tools before ascertaining that they have a measurable impact, it is still useful to be aware of this.

AutoMapper may result in performance costs both at startup (when mapping configurations are set up) and during processing (when actually mapping happens), and these costs might not be negligible for larger projects. As a result, it is good to measure these costs to ensure they don’t get out of hand.

So What Should We Use Instead?

As it turns out, the C# language is perfectly capable of doing DTO mapping, and no library is actually necessary (the same argument applies to Fluent Validations, by the way).

The SDS article suggests simply using methods for mapping, and goes on to list the benefits in terms of refactoring, testing, performance and code quality. My own “The Adapter Design Patterns for DTOs in C#” takes this a step further and suggests using extension methods as an elegant, decoupled solution.


You might have noticed that I’ve talked a lot about Validity, Performance and Maintainability, but I haven’t really mentioned Timeliness at all. Surely AutoMapper is a time-saver, as we have to write a lot less code? Well, no, actually.

The SDS article compares manual mapping to AutoMapper, and concludes that the latter actually requires a lot more effort (it’s not all about lines of code). I also argued in “The Adapter Design Patterns for DTOs in C#” that “writing AutoMapper configuration can get very tedious and unreadable, often more so than it would take to map DTOs’ properties manually”.

But beyond that, as I mentioned earlier, it actually doesn’t take a lot of time to write a few lines of code to map properties from one object to another. In fact, in practice, I’ve spent way more time fixing problems resulting from AutoMapper, or in discussions about all the points I’ve written in this article.

The only time when automatic mapping can really save time is when you have hundreds of DTOs and you don’t want to manually map them one by one. This is a one-time job, and should be done by code generation, not runtime mapping. Code generation has been around for a long time, and is given particular prominence in “The Pragmatic Programmer” by Andrew Hunt and David Thomas.

In the .NET world, code generation was most famously used by the Entity Framework, when the old Database First approach used T4 templates to generate model classes based on database tables. While T4 templates never really became popular, and they are no longer supported by .NET Core, it is not a big deal to write some code to read classes from a DLL via Reflection and spit out mapping code based on their properties. In fact, I wouldn’t be surprised if something that does this already exists.

Update 22nd April 2021: It does! Cezary Piątek developed MappingGenerator, a Visual Studio plugin that quickly generates mapping logic from one DTO to another.

Code generation is preferable over runtime automapping because it’s done as a one-time, offline process. It does not affect build time or startup time, does not cause problems at runtime (the generated code still has to be compiled), and does not need additional libraries or dependencies within the project. The generated code can easily be read, debugged and tested. And if there are any properties that require custom logic that can’t be generated as part of this bulk process, you just take the generated code and manually add to it (which you would have done anyway with AutoMapper).


Laziness is often promoted as a good thing in software developers, because it makes them automate things. However, it’s not okay to automate things in a way that sacrifices validity, performance, maintainability or timeliness.

Further reading

This section was added on 22nd April 2021.

Gathering Net Salary Data with Puppeteer

Tax is one of those things that makes moving to a different country difficult, because it varies wildly between countries. How much do you need to earn in that country to maintain the same standard of living?

You can, of course, use an online salary calculator to understand how much net salary you’re left with after deducting tax and social security contributions, but this only lets you sample specific salaries and doesn’t really give you enough information to assess how the impact of tax changes as you earn more. Importantly, you can’t use these tools to draw a graph for each country and compare.

Malta Salary Calculator by Darren Scerri

Fortunately, however, these tools have already done the heavy lifting by taking care of the complex calculations. To build a graph, all we really need to do is to take samples at regular intervals, say, every 1,000 Euros. Since that is very tedious to do by hand, we’ll use a browser automation tool to do this for us.

Enter Puppeteer

Puppeteer, as the homepage says, “is a Node library which provides a high-level API to control Chrome or Chromium”, which is pretty much what we need for this job. It also gives us what we need to get started. In a new folder, run the following to install the puppeteer dependency:

npm i puppeteer

Then, create a new file (e.g. netsalary.js) and add the starter code from the Puppeteer homepage. We’ll use this as a starting point:

const puppeteer = require('puppeteer');

(async () => {
  const browser = await puppeteer.launch();
  const page = await browser.newPage();
  await page.goto('https://example.com');
  await page.screenshot({ path: 'example.png' });

  await browser.close();

Getting Salary Data for Malta

In this particular exercise, we’ll get the salary data for Malta using Darren Scerri’s Malta Salary Calculator, which is relatively easy to work with.

Before we write any code, we need to understand the dynamics of the calculator. We do this via the browser’s developer tools.

Whenever you change the value of the gross salary input field (that has the “salary” id in the HTML), a bunch of numbers get updated, including the yearly net salary (which has the “net-yearly-result” class) which is what we’re interested in.

Just by knowing how we can reach the relevant elements, we can write our first code to retrieve the input (gross salary) and output (yearly net salary) values to make sure we know what we’re doing:

const puppeteer = require('puppeteer');

(async () => {
  const browser = await puppeteer.launch();
  const page = await browser.newPage();
  await page.goto('http://maltasalary.com/');
  // Gross salary
  const grossSalaryInput = await page.$("#salary");
  const grossSalary = await page.evaluate(element => element.value, grossSalaryInput);
  console.log('Gross salary: ', grossSalary);
  // Net salary
  const netSalaryElement = await page.$('.net-yearly-result');
  const netSalary = await page.evaluate(element => element.textContent, netSalaryElement);
  console.log('Net salary: ', netSalary);

  await browser.close();

Here, we’re using the page.$() function to locate an element the same way we would using jQuery. Then we use the page.evaluate() function to get something from that element (in this case, the value of the input field). We do the same for the net salary, with the notable difference that in the page.evaluate() function, we get the textContent property of the element instead.

If we run this (node netsalary.js), we should get the same default values we see in the online salary calculator:

We managed to retrieve the gross and net salaries from the online calculator.

Text Entry

That was easy enough, but it used the default values that are present when the page is loaded. How do we manipulate the input field so that we can enter arbitrary gross salary values and later pick up the computed net salary?

The simplest way to do this is by simulating keyboard input as follows:

const puppeteer = require('puppeteer');

(async () => {
  const browser = await puppeteer.launch();
  const page = await browser.newPage();
  await page.goto('http://maltasalary.com/');
  const grossSalary = 30000;
  // Gross salary - keyboard input
  await page.focus("#salary");
  for (var i = 0; i < 6; i++)
    await page.keyboard.press('Backspace');
  await page.keyboard.type(grossSalary.toString());
  // Net salary
  const netSalaryElement = await page.$('.net-yearly-result');
  const netSalary = await page.evaluate(element => element.textContent, netSalaryElement);
  console.log('Net salary: ', netSalary);

  await browser.close();

Here, we:

  1. Focus the input field, so that whatever we type goes in there.
  2. Press backspace six times to erase any existing gross salary in the field (if you check the online calculator, you’ll see it can take up to six digits).
  3. Type in the string version of our gross salary, which is a hardcoded constant with a value of 30,000.

The result I get when I run this matches what the online calculator gives me. I guess I must be doing something right for once in my life.

Net salary:  22,805.44

Pulling Net Salary Data in a Range

So now we know how to enter a gross salary and read out the corresponding net salary. How do we do this at regular intervals within a range (e.g. every 1,000 Euros between 15,000 and 140,000)? Easy. We write a loop.

In practice, there’s a little timing issue between iterations, so I also needed to nick a very handy sleep function off Stack Overflow and put a very short delay after doing the keyboard input, to give it time to update the output values.

const puppeteer = require('puppeteer');

function sleep(ms) {
  return new Promise(resolve => setTimeout(resolve, ms));

(async () => {
  const browser = await puppeteer.launch();
  const page = await browser.newPage();
  await page.goto('http://maltasalary.com/');
  console.log('Gross Net');
  for (var grossSalary = 15000; grossSalary <= 140000; grossSalary += 1000) {
    // Gross salary - keyboard input
    await page.focus("#salary");
    for (var i = 0; i < 6; i++)
      await page.keyboard.press('Backspace');
    await page.keyboard.type(grossSalary.toString());
    await sleep(10);
    // Net salary
    const netSalaryElement = await page.$('.net-yearly-result');
    const netSalary = await page.evaluate(element => element.textContent, netSalaryElement);

    console.log(grossSalary, netSalary);

  await browser.close();

This has the effect of outputting a pair of headings (“Gross Net”) followed by gross and net salary pairs:

Outputting the gross and net salaries in steps of 1,000 Euros (gross) at a time.

Making a Graph

Now that we have a program that spits out pairs of gross and net salaries, we can make a graph out of this data. First, we dump all this into a file.

node netsalary.js > malta.csv

Although this is technically not really CSV data, it’s still very easy to open in spreadsheet software. For instance, when you open this file using LibreOffice Calc, you get the Text Import screen where you can choose to use space as the separator. This makes things easier given that the net salaries contain commas.

Choose Space as the separator to load the data correctly.

Once the data is in a spreadsheet, producing a chart is a relatively simple matter:

Graph showing how net salary changes with gross salary in Malta.

Now, this graph might look a little lonely, but you can already gather interesting insight by noticing its gradient and the fact that it isn’t entirely straight.

After doing this exercise for multiple countries, it’s fascinating to see how their lines compare when plotted on the same chart.

Aside from the allure of data analysis, I hope this article served to show how easy it is to use Puppeteer to perform simple browser automation, beyond the obvious UI automation testing.

Jack of All Trades, Master of None

“Jack of all trades, master of none,” I’ve heard IT industry professionals scoff arrogantly several times in the past. That was their judgement of polyglot programmers, full stack developers, or any other people who had dabbled in more than one area of the kind of work we do.

Full stack. Heh heh. I took this picture at an eatery in San Francisco in February 2017.

I get where they’re coming from. Our industry is a very complicated one, and it’s really hard to learn much of anything if you don’t focus. Whether we’re talking about backend, frontend, databases, NoSQL and so on, there is an overwhelming number of technologies to discover and learn, and the information overload on the internet doesn’t help digest them.

The conventional wisdom is to be a “jack of all trades, master of one“, meaning you learn a number of different things but try to excel at at least one of them. This is great advice, but I’ve very rarely seen it happen in practice. People tend to either specialise in one thing in depth, or have a superficial knowledge of different things. Which of these would you choose?

Being just a master of one is a real problem I’ve seen for a long time. People who have only focused on one programming paradigm throughout their training and career tend to have trouble thinking outside the box and finding different ways to solve problems. Backend and frontend skills don’t easily transfer across, and most full stack developers are typically much stronger at one of these than the other. Most developers don’t understand enough about security, infrastructure and architecture.

The way I see it, that’s pretty bad. A developer who knows nothing about servers is a bit like a centre-forward who is so good that he can dribble past the opposing team’s defence, but fails to score every time.

That’s why even a semi-decent University education in this field doesn’t just teach programming. Learning CPU architecture, systems programming, Assembly language or C gives an idea what happens under the hood and teaches a certain appreciation of resources and doing things efficiently, a perspective that people having only experience with high-level languages often dismiss. Having a basic grasp of business and management prevents developers from idolising their code (“clean code” anyone?) and helps them to focus on solving real problems. Understanding a little about infrastructure helps them better understand architectural and security concerns that code-focused developers will often ignore.

Universities, in fact, produce instances of “jack of all trades, master of none”. Let’s face it: when you graduate, although your scores might give you confidence, you don’t really know much of anything. But thanks to your holistic training, you’re able to understand a variety of different problems, and gradually get a deeper understanding of what you need to solve them.

I also think there is a place for the “master of one” type of people who specialise very strongly in one area and mostly ignore the rest. I imagine these would be academics, or R&D specialists in big companies like Google. But, as much as we like drawing inspiration and borrowing ideas from successful companies, we always have to keep the context in mind. Who are we kidding? Most of us mere mortals don’t work at companies anything like Google.

So what I’m saying here is: it’s not bad to be a “jack of all trades, master of none” in our field. It is obviously better if you’re also “master of one”, but if I had to choose, I’d be (or hire) the one with the broad but superficial knowledge. Because when you are aware that something exists, then it’s not a huge leap to research it in more detail and get to the depth you need. It’s actually a good strategy to learn depth on an as-needed basis, especially given that you’ll never have enough time to learn everything in depth.

As in life, I’d rather know a little bit about many things that interest me, than bury myself in one thing and otherwise give the impression that I’ve been living under a rock.

Enabling and Enforcing HTTPS on a Subdomain with cPanel

Nowadays, there’s really no excuse not to enable HTTPS on a website, even a small personal one. It’s free and simple. In fact, chances are that whatever host you’re using offers a simple option you can just turn on. In this article, we’ll see how to set this up in cPanel, which is commonly used in Linux/PHP/MySQL web hosting services.

Set up the Subdomain

Subdomains service in cPanel

If you haven’t already, create a subdomain. To do this:

  1. Locate the Subdomains service in cPanel.
  2. Enter a name for the subdomain.
  3. Enter a path to a folder to be used as the document root for the subdomain.
  4. Click the Create button.

Enable HTTPS on the Subdomain

Let’s Encrypt™ SSL service in cPanel

New subdomains will by default run on HTTP, which is insecure. Enabling HTTPS requires an SSL or TLS certificate. To set this up:

  1. Locate the Let’s Encrypt™ SSL service in cPanel.
  2. Scroll towards the bottom of the page, and page through your subdomains until you locate the new one you want to apply HTTPS to.
  3. Click on the Issue action link next to it.
  4. Leave the settings as they are and click on the Issue button.

Enforce HTTPS on the Subdomain

Domains service in cPanel

Enabling HTTPS is only half good if people can still access the site insecurely over HTTP. It’s very easy to automatically redirect people from the HTTP endpoint to HTTPS. To do this:

  1. Locate the Domains service in cPanel.
  2. Locate the new subdomain, which may be on a different page.
  3. Turn on the switch in the Force HTTPS Redirect column.
  4. A success message should confirm that it’s been enabled.

Test the Subdomain

The subdomain is secure and running on HTTPS

To make sure everything is set up correctly, use a browser to ensure that the website at your subdomain is secure.

  1. Wait a few seconds. The redirect you just enabled might not kick in right away.
  2. Use an incognito session in your browser. Otherwise, if you visited the subdomain before enabling the redirect, it’s possible that the browser might still show it as insecure.
  3. Access your domain with the URL starting with https://. Ensure that your browser displays the padlock icon and reports the connection as secure.
  4. Access your domain with the URL starting with http://. Once the page loads, ensure that you are now on https:// and that the browser displays the padlock icon and reports the connection as secure. Optionally, you can also open your browser’s dev tools, switch to the Network tab, and observe a 301 redirect request.


As you can see, it’s super easy to get HTTPS working on a subdomain in cPanel. Just enable HTTPS for the subdomain, force the HTTPS redirect, and you’re done.

Azure Fundamentals Part 5 Summary

This is a summary of the Azure Fundamentals part 5: Describe identity, governance, privacy, and compliance features learning path. Aside from the usual “Introduction to Azure Fundamentals” module, repeated in every learning path in this series, there are three modules covering identity, cloud governance, and compliance, respectively. If you’re a developer, this learning path is easily the most boring of the lot, but it’s also very important from a cloud administration point of view.

Identity Services

This is a summary of the Secure access to your applications by using Azure identity services module. They love using wordy headings, don’t they?

Authentication vs authorization: who you are vs what you have access to.

Azure Active Directory (Azure AD):

  • Similar to Active Directory, but for the cloud
  • Monitors sign-in attempts, unlike the on-premises counterpart
  • Controls access to other Microsoft services such as Office 365
  • Has the concept of tenants, which represent organisations
  • Is an identity and access management service. It stores information about users (including passwords), and provides control over them (e.g. reset password, multifactor authentication, list of banned passwords, etc)
  • Also provides device management – devices can be registered to control which devices are allowed to access services.
  • Supports Single sign-on (SSO) to access multiple applications with the same credentials.
  • Azure AD Connect synchronises user identities between on-premises Active Directory and Azure AD. Users can use their same credentials to access on-premises and cloud services.

Multifactor authentication provides an additional layer of security over the usual username and password by requiring two or more authentication mechanisms, typically from the following categories:

  • Something the user knows (e.g. username and password)
  • Something the user has (e.g. code sent to mobile device)
  • Something the user is (biometric data, e.g. fingerprint)

Conditional access is a feature of Azure AD that applies multifactor authentication differently based on identity signals. This is basically a rule engine that can do things like request the second factor only if they’re in an unknown location, signing in from an unknown device, or accessing a particular application. Access could also be blocked entirely in some circumstances (e.g. signing in from a high-risk country). Conditional access is a premium feature that requires a special Azure AD licence.

Cloud Governance

This is a summary of the Build a cloud governance strategy on Azure module.

The Cloud Adoption Framework for Azure guides you towards migrating to the cloud. There are five steps:

  • Define your strategy: understand what benefits you’ll gain by moving to the cloud, get everyone on board, and choose the right proof of concept project to kick it off.
  • Make a plan: take stock of what you have on-premises, train up, and make a plan to migrate.
  • Ready your organisation: set up your Azure subscriptions and create a landing zone, basically an environment in the cloud to get you started.
  • Adopt the cloud: start migrating, review best practices, find ways to migrate more efficiently, and study ways to handle more complex migrations.
  • Govern and manage your cloud environments: define processes and policies that will apply to resources in the cloud, and maintain them as they evolve throughout the migration process.

Things to consider when deciding how to organise Azure subscriptions:

  • BIlling: you can create one billing report per subscription, so you can organise subscriptions by department or project.
  • Access control: subscriptions provide inherent isolation (e.g. between development and production environments).
  • Subscription limits: some resources are limited in the amount you can deploy per subscription, so you’ll need to allocate more subscriptions if necessary.

Role-based access control (RBAC) is used to grant or restrict access to resources. These roles are applied to a scope that could be:

  • A management group
  • A single subscription
  • A resource group
  • A single resource

Access control is inherited by child scopes, e.g. assigning a role to a single subscription means it is also applied to all resource groups and resources in that subscription.

RBAC is managed via Access control (IAM) in the Azure portal. RBAC rules are applied to any request to an Azure resource that passes through the Azure Resource Manager.

RBAC uses an allow model, so as long as you have a role that allows you to perform an action, you can do it; and if different roles give you different access (e.g. read and write), then they sum up (e.g. you get both read and write).

Resource locks are a simple setting against accidental modification or deletion. You can use either CanNotDelete (authorised users can read or write but not delete) or ReadOnly (authorised users can read a resource but can’t change or delete it). You can remove the lock to perform the restricted operation (e.g. to delete the resource).

You can use Azure Blueprints (more on this further below) to set a standard for resources across your organisation, which could include enforcement of resource locks among other things.

Resource tags are used to apply metadata to resources. They complement subscriptions and resource groups as another way to categorise and organise things. They help to:

  • Manage resources and locate them easily
  • Report on costs by particular tags
  • Group resources based on criticality and SLAs
  • Classify data security (e.g. confidential)
  • Regulatory compliance (e.g. ISO27001)
  • Run any kind of automation logic on resources with a particular tag

Azure Policy lets you create and enforce policies or initiatives (groups of policies) that apply to resources. To implement a policy, you:

  1. Create a policy definition
  2. Assign it to resources
  3. Review the evaluation results

A policy definition can be used to do things like:

  • Prevent VMs from being deployed in certain regions
  • Restrict which virtual machine sizes can be deployed
  • Enforce MFA on accounts with write permissions
  • Prevent CORS from allowing unrestricted access to web applications
  • Ensure updates are installed on VMs

Azure Blueprints lets you orchestrate things like role assignments, policy assignments, ARM templates and resource groups across your organisation so that you don’t need to set them up for each subscription. Blueprints are made up of artifacts, and they deploy different elements to each subscription (e.g. Allowed locations policy, resources from an ARM template, etc).

Data Protection & Compliance

This is a summary of the Examine privacy, compliance, and data protection standards on Azure module.

Some projects require compliance with certain standards, such as ISO 27001 or government-specific regulations. Azure is compliant with a huge number of these, so it’s quite likely you can use Azure even when working in some of the more regulated sectors.

You can also check the following documents:

  • Microsoft Privacy Statement: how Microsoft manages personal data
  • Online Services Terms: agreement between customer and Microsoft when using services such as Azure or Office 365
  • Data Protection Addendum: more specific about data protection

The Trust Center lets you find information about particular compliance offerings, such as ISO 27001, and how it applies to cloud services on Azure.

The Azure compliance documentation describes how Azure adheres to certain standards, e.g. PCI DSS.

Azure Government is a separate Azure offering for US government. It has the highest level of security, and data centres are physically isolated so they can’t be used by you and me outside the scope of the US government.

Azure China 21Vianet is the Azure offering in China. Microsoft can’t operate Azure directly in China because of local regulations, so they instead offer it via a partner, 21Vianet. Services offered are mostly the same, but they may vary a little.

"You don't learn to walk by following rules. You learn by doing, and by falling over." — Richard Branson