Bandit keep alives not working in apache bench

gregors

Question y’all,

When I play with apache bench (ab) and I use the -k flag the output for the runs have this

Keep-Alive requests:    0

However if I try Cowboy for example it seems to report correctly

Keep-Alive requests:    15000

as well as being a bit faster (due to reused connections no doubt). I tried this with a few other languages, golang etc and they seemed to handled keep alives with ab.

Now I did an initial search through Bandit docs but I’m not seeing any settings pertaining to this. I did see a small blurb saying it was supported in http/1.1. Ok hmmmmmmmmmm.

What exactly is ab pushing out? Let’s spin up tcdump

sudo tcpdump -i any -A 'port 4000'

GET /health-check HTTP/1.0                                                                                                               
Connection: Keep-Alive                                                                                                                           
Host: 127.0.0.1:4000                                                                                                                             
User-Agent: ApacheBench/2.3                                                                                                                      
Accept: */*

huh http/1.0 so I’m guessing Bandit just doesn’t support keep alives in that version. I don’t know exactly what the difference is, I should probably read the http spec at some point, but I am asking if there’s an easy way I can configure Bandit to support that. No problem if there isn’t an easy way. I’m just having fun. But it does look like other servers do support this…probably for ab use cases

6 comments

/phoenix #bandit

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2024-02-18 15:04:52 UTC

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mtrudel

Creator of Bandit

Thanks for the PR; it’s merged!

I’ll echo what others have said here; ab is in general a pretty outdated program that does a lot of oddball stuff like this (IIRC, this was actually strictly out of spec prior to the RFC911x series).

Post #6

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LostKobrakai

A quick google suggests keep-alive wasn’t officially supported before http 1.1, but was added as a response to people using it with http 1.0 without a spec for it existing. So it’s a question of how spec compliant bandit wants to be. A toggle might be a reasonable middleground.

Post #2

gregors

Update after some weekend time to dig into this…

github.com/mtrudel/bandit

allow http/1.0 to work with mixed-case Keep-Alive (#308)

main ← gregors:make_http_10_use_keepalive

opened 05:19AM - 18 Feb 24 UTC

gregors

+12 -0

tldr; Is that certain clients (in this case apache bench) will send http/1.0 req…uests with "Keep-Alive" and not "keep-alive" and we currently don't respect that. I noticed this issue while comparing ab to other servers which seem to handle this correctly. I originally asked about this behavior in the [elixir forums](https://elixirforum.com/t/bandit-keep-alives-not-working-in-apache-bench/61672) After taking a look and doing some debugging I saw that we fail to lower-case the connection header prior to comparison. Instead of incurring the penalty of lower-casing the entire header I'm assuming the mixed-case pattern match is a performant solution? Strictly speaking we probably should lower-case it to be "compliant" I did look at the `get_connection_header_keys/1` function but it didn't really look like a good fit since it returns that list. Happy to hear feedback and change anything.

Post #5