https://segflow.github.io/tags/sysctl/Recent content in Sysctl on SegflowHugoen-usMon, 22 Mar 2021 18:30:00 +0100https://segflow.github.io/post/million-idle-connections/Mon, 22 Mar 2021 18:30:00 +0100https://segflow.github.io/post/million-idle-connections/<p>I had been telling people for months that Go can &ldquo;trivially&rdquo; hold a million idle TCP connections. The runtime uses epoll, goroutines are cheap, what could go wrong. Then a colleague asked me to actually do it, and I realised I had never tried. So I sat down with my laptop, a fresh <code>net.Listen</code>, and a client that just wants to open a lot of sockets.</p> <p>The first wall I hit was 1024 file descriptors. After that came five more walls in quick succession, none of them in user code. This post is the log of every wall I walked into and how to move it. Code, logs, and scripts are in the <a href="./million-idle-connections/code/">scratch directory</a>.</p>