Source: http://habrahabr.ru/company/wargaming/blog/231065/

Part 1: http://ftr.wot-news.com/2014/07/26/how-xvm-was-created-part-1/
Part 2: http://ftr.wot-news.com/2014/07/28/how-xvm-was-created-part-2/

Last part of the article.

User Support

The developers understood from the start that XVM is more difficult to install than other regular mods and that not many would use it without the user support. In order to reduce the support load, XVM was split into XVM-full and XVM-light and as mentioned in the previous part, the light version had everything related to player statistics removed. That’s why the players with light version did not have to install neither Dokan nor .NET application, which seriously simplified the installation.

The very first user support was made via the regular World of Tanks forum. This was not very convenient – the developers did not have the option to moderate and edit threads, the players were confusing the support thread with other threads that were not related in any way to the developers. That’s why as soon as the mod started working on a dedicated server (January 2012), a new support forum was estabilished there. It was a vanilla phpBB and despite that, it fulfilled its function until that one time where there was an emeregency.

The emeregency was a result of the situation, when the developers had to resize the sections of the file system. Why was that necessery – noone can remember, but it was apparently needed. At that point the developers did not have any specialists for that, so decided to do it by themselves. The result of that was broken RAID and there were (surprise!) no actual backups made. The positive thing about that was that Mr 13 joined the developer team (he did backups), who was also the owner of Korean Random forums, on which the main support resource of XVM is currently located.

In Fall 2012, the mod recieved its own website (www.modxvm.com) with mod description, links, FAQ etc. – online config editor was also moved there. In time, the site got translated to English, German, French and Ukrainian. The site also helped to reduce the costs of the XVM development, as the donations from players did not cover the development costs (or even a small part of it) – but there was some discrepancy there. The developers, using their own tools noticed that the amount of unique XVM users rises every month, at one point, it reached over a million, but the amount of unique accesses on the site per month was less than 100k. They knew the reason for that: modpacks – those are sets of mods, promoted by some “celebrities” and named after them. They liked to include XVM in those sets, but without the links leading to it. It went as far as some of them replacing the xvm link during the loading screen with a link to their own site. The developers did not like this parasitism and a voluntary-mandatory statistics module activation was created on the XVM site.

It works like this:

- the user goes to XVM site
- he logs in, using the Wargaming ID (OpenID)
- thanks to that, devs learn that player’s nickname and ID and tag him as “requesting token”
- after that, the user runs the client with XVM, the mod, when starting, issues a request to the /checkToken method. As a reply, the user (with “requested token” status) recieves the token itself (GUID), otherwise there is only “active” or “non active” status, depending on whether the client has activated tokens or not. The tokens recieved are saved in the file \res_mods\xvm\db\tokens.xdb
- during each request to our API, the client also sends this token
- if the token is missing or obsolete (its duration is two weeks), the data are not sent and the client displays an error message, telling you to go to the mod site and to request an activation of the statistics there
- the client can recieve up to five tokens (if you play your account on multiple PC’s)

This activation procedure had two effects:

- the amount of site users matched the amount of mod users
- the statistics server load dropped by cca 30 percent

The devs think that the second effect was because some users of all those modpacks did not need the statistics module, they used only because it was enabled by default in the majority of those modpacks.