Limit bandwidth by Openresty
Nginx has two cool features to limit bandwidth for responses:
For instance, this works well, but absolutely not well for video streamings:
location / {
limit_rate_after 500k;
limit_rate 50k;
...
}
This means, that you can buffer the stream for 500k then rate drops until 50k, but if you watch the video using the browser/player/whatever you will notice that with every new buffer chunk the browser will issue a new request which means new limits.
What if I want to push those limits only for video streamings and not for the poor wget? I mean - with every next request to the same URI lower limits in reverse exponentially manner, like reverse TCP congestion behavior.
Everything Should Be Made as Simple as Possible, But Not Simpler
TL;DR; - create SHA256 hash for full URI with 5 minutes expiration time and increment the counter with every new request. This counter is used for exponentially decreasing the bandwidth for responses (bytes per second):
26214400
6553600
1638400
409600
102400
25600
6400
...
router.conf:
location / {
set $limit_rate '';
set $limit_rate_after '';
access_by_lua_file conf/router.lua;
proxy_buffering on;
...
}
NOTE: If you use proxy_pass you must enable proxy_buffering on.
router.lua:
local request_count = function ()
local resty_sha256 = require "resty.sha256"
local str = require "resty.string"
local sha256 = resty_sha256:new()
sha256:update(ngx.var.http_host .. ngx.var.request)
local digest = sha256:final()
local key = "request:" .. str.to_hex(digest)
local ok, err = redis:connect("127.0.0.1")
if not ok then
return nil, err
end
local ok, err = redis:auth("something")
if not ok then
return nil, err
end
local data, _ = redis:get(key)
redis:incr(key)
redis:expire(key, 300)
return data
end
local bw_limit = 104857600
if request_count() ~= ngx.null then
bw_limit = math.max(10240, math.floor(bw_limit / 2 ^ request_count()))
end
ngx.var.limit_rate = bw_limit
ngx.var.limit_rate_after = 8388608
What is your biggest wish? To eject this shit out of my ass.