I'm attempting to limit the bandwidth available to a running ruby process to prevent it flooding our link and affecting other traffic. The process is downloading large files over HTTP.I've found numerous people suggesting trickle as a convenient userland-only option (like https://unix.stackexchange.com/a/34123/160146).I've tested it with an scp download and confirmed it limits the download rate:trickle -s -d 50 scp user@example.com localfile.datI've also tested a python 2.7 script and confirmed it limits the download rate:# cat test.pyimport urllibtestfile = urllib.URLopener()testfile.retrieve(http://example.com/bigfile.dat)# trickle -s -d 50 python test.pyFinally, I've tested with a basic ruby script and trickle has no effect. The scripts maxes out my downstream bandwidth:# cat test.rb require 'net/http'Net::HTTP.get_response(URI.parse(http://example.com/bigfile.dat))# trickle -s -d 50 ruby test.rbI've tested with ruby 2.1, 2.2 and 2.3 with no difference in behaviour.I notice the trickle documentation says it only works with dynamically linked programs, but I'm fairly sure thats the case for me. I'm using the ruby provided by Debian in /usr/bin, and ldd reports linked libraries:# ldd /usr/bin/ruby2.3         linux-vdso.so.1 (0x00007fffdcdc6000)        libruby-2.3.so.2.3 => /usr/lib/x86_64-linux-gnu/libruby-2.3.so.2.3 (0x00007f277e11a000)        libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007f277defd000)        libgmp.so.10 => /usr/lib/x86_64-linux-gnu/libgmp.so.10 (0x00007f277dc79000)        libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007f277da75000)        libcrypt.so.1 => /lib/x86_64-linux-gnu/libcrypt.so.1 (0x00007f277d83e000)        libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007f277d538000)        libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f277d194000)        /lib64/ld-linux-x86-64.so.2 (0x0000558796396000)Interestingly, trickle can rate limit my ruby process if I use the curb (libcurl bindings) gem:# cat test.rbrequire 'curb'http = Curl.get(http://example.com/bigfile.dat))# trickle -s -d 50 ruby test.rbDoes that suggest that ruby's default Net::HTTP library uses sockets in a way that's incompatible with trickle?I'm out of ideas. Is there a fixed reason why trickle doesn't work with ruby or is there something I can do to get them working together?
Why doesn't rate limiting with trickle work with ruby?
linux;networking;ruby
I believe I've tracked this down. It's arguably a fault in trickle that's occurred as a result of creeping featurism in the socket() library call.The trickle code redefines socket(), as you know. At the top of its reimplementation in the file trickle-overload.c it has a check that includes type == SOCK_STREAM so that only connections of type SOCK_STREAM are eligible for processing.The ruby code opens the socket with type = SOCK_STREAM | SOCK_CLOEXEC. The SOCK_CLOEXEC is a Linux extension (since 2.6.27) that avoids the use of a subsequent fcntl call to set the close-on-exec flag.Unfortunately SOCK_STREAM is not the same as SOCK_STREAM | SOCK_CLOEXEC so the trickle processing will not take place until its code is fixed to allow for the extensions now permitted within socket's type field.I know of no workaround other than to recompile trickle for your system with a modified socket type comparison.(I've submitted a bug report to Debian Bugs since that's my preferred platform.)