~ The time an HTTP request takes to pass through a proxy, a proxy, a proxy, a proxy, ...
» By Joren on Thursday 16 January 2025A discussion at work led to the question how much time it takes for a HTTP request to pass through a HTTP proxy. This blog post deals with this question by measuring a request passing through a stupid amount of HTTP proxies.
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curl -s -o /dev/null -w "%{time_starttransfer}\n" http://localhost:2000
Fig: Measuring the time it takes to pass 500 proxies with Curl.
In modern development setups it is not uncommon that your HTTP request passes a few HTTP proxies before reaching a final server that actually handles the request. In our case there is a proxy which ensures an SSL certificate, which is forwarded to a proxy which automatically forwards requests to a docker container. A final HTTP proxy runs in the docker network that forwards the request to a webserver. A response follows the same way in reverse.
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#Caddyfile, to pass through 500 HTTP proxies
:2000 {
reverse_proxy localhost:2001
}
:2001 {
reverse_proxy localhost:2002
}
...
:2500 {
respond "Hello, proxy!"
}
Fig: Configuration to pass a HTTP request through many proxies. The final response is a simple text.
To measure the time it take to pass through a HTTP proxy, I wrote a small script to start 500 separate instances of the Caddy webserver configured as a HTTP/2 proxy. Then, I measure the time it takes to pass through all 500 of the HTTP proxies or only 490, 480,… which results in the graph below.
Fig: Time it takes to pass x amount of HTTP proxies. The y-axis represents the time taken (in seconds), and the x-axis indicates the number of HTTP proxies passed.
So each proxy pass takes about 0.4 milliseconds in one of the best cases, where requests are forwarded from and to localhost. Network overhead adds to that but assuming that interconnects are fast, adding a few HTTP proxies does not affect latency in a meaningful way. Of course it is best to evaluate your situation and measure
UGent
measure.rb, script.rb, and proxy_time_graph.png
In my house, I have a few smart home features: to control ventilation, to open and close solar screens, and to switch a few smart sockets. Up until a couple of days ago, the ventilation and screen controllers operated using custom software running on an ESP32. However, configuring, maintaining, upgrading, and integrating with this custom software gradually became a headache.