Describes how to change integration in lobbies to leverage new BAR CDN setup for distributing game and maps.
As part of the “BAR launcher is speed” project I realized that current hosting of game assets is not meeting the needs of global BAR community. Both maps and game distribution happens from the central server in Germany which is problematic for players from outside of Europe. To mitigate this, I’ve set up an alternative assets hosting mechanism that mirrors required assets and allows for more reliable delivery.
BAR game files are currently being distributed by the Rapid system. To download from it there is a dedicated tool pr-downloader. This document will focus on how to configure it to leverage new hosting. Maps are being downloaded from https://springfiles.springrts.com/ and downloading them is also supported by pr-downloader but some lobbies have a more direct integration.
ℹ️ NOTE: It’s important to use the BAR fork of pr-downloader (distributed together with BAR engine), as upstream doesn’t have required changes.
To download game via pr-downloader from CDN lobby needs to set 2 environment variables when launching binary:
PRD_RAPID_USE_STREAMER=falsePRD_RAPID_REPO_MASTER=https://repos-cdn.beyondallreason.dev/repos.gz
If pr-downloader is also called from the game (e.g. Chobby), the same environment variables need to be also set when launching spring binary.
Additionally an option must be set in springsettings.cfg configuration file to make sure that game resolves rapid tags from the correct repository:
RapidTagResolutionOrder = repos-cdn.beyondallreason.dev
ℹ️ NOTE: If lobby supports changing the repo back to the default, it must also clear RapidTagResolutionOrder tag when doing so.
For initial game download when there aren't any files present in the pool directory, it's highly preferred to download a pool preseed file that contains periodically build (currently weekly) game files: https://pool-init.beyondallreason.dev/data.7z and unpack it to the pool directory following with regular pr-downloader run.
The goal of that is to significantly reduce bandwidth cost of the CDN hosting rapid, shifting it to CDN that is much more cost efficient for bandwidth and single big file downloads but is not suitable for quick partial updates.
The only required change is to set one additional environment variable:
PRD_HTTP_SEARCH_URL=https://files-cdn.beyondallreason.dev/find
Same variable must be also set to spring binary if the loaded mod is downloading maps too (e.g. Chobby).
Lobby needs to call https://files-cdn.beyondallreason.dev/find endpoint using GET method with 2 url parameters
categoryequal tomap, andspringnameof the map.
For example to fetch info about “Angel Crossing 1.4”: https://files-cdn.beyondallreason.dev/find?category=map&springname=Angel%20Crossing%201.4
It will return JSON encoded map metadata in the same format as returned from springfiles. Example formated response:
[
{
"filename": "angel_crossing_1.4.sd7",
"springname": "Angel Crossing 1.4",
"md5": "9fc29b4e9dd666d9f9866280fb3c0861",
"category": "map",
"path": "maps",
"tags": [],
"size": 83728479,
"timestamp": "2022-06-18T19:37:47",
"mirrors": [
"https://files-cdn.beyondallreason.dev/file/cn2874nc987r239nrx873qny4/angel_crossing_1.4.sd7"
]
}
]ℹ️ NOTE: Unlike real springfiles, this endpoint doesn’t support full search, and will error if result from springfiles would return multiple entries. It's guaranteed to always return a single entry or a HTTP error like Not Found.
With that metadata information lobby must:
- Fetch file pointed by
mirrorsproperty. Lobby must not make any assumptions about the returned URLs. In case multiple are returned: it should choose one at random. - Save the downloaded file to a temporary location.
- Verify that the md5 sum from metadata matches the downloaded file.
- Move the verified map to the destination location
maps/{filename}wherefilenameis property from the metadata, not basename from mirror URL, e.g.maps/angel_crossing_1.4.sd7