Date: Thu, 25 Aug 2016 11:56:37 +0200 From: Jan Bramkamp <crest@rlwinm.de> To: Jonathan de Boyne Pollard <J.deBoynePollard-newsgroups@NTLWorld.com>, Adrian Chadd <adrian@freebsd.org>, Supervision <supervision@list.skarnet.org>, FreeBSD Hackers <freebsd-hackers@freebsd.org> Subject: Re: Linuxisms in s6 Message-ID: <ffc52048-67da-a0bb-d24a-275b7578b858@rlwinm.de> In-Reply-To: <37d5159b-4957-42f8-2252-fa53d7446bb6@NTLWorld.com> References: <37d5159b-4957-42f8-2252-fa53d7446bb6@NTLWorld.com>
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On 25/08/16 06:53, Jonathan de Boyne Pollard wrote: > http://adrianchadd.blogspot.co.uk/2016/08/freebsd-on-tiny-system-whats-missing.html?showComment=1471236502051#c1305086913155850955 > , Adrian Chadd: > >> We're using s6 at work, and it works out mostly ok. Mostly once you >> get around the linuxisms, and the lack of sensible time code in it >> (its calculations for daemon run duration is based on system time, not >> wall clock, so if your box boots jan 1, 1970 then gets NTP, things >> are.. hilarious), and some of the arcane bits to get logging working >> right. >> > What are these Linuxisms in s6? s6-linux-utils and s6-linux-init have > Linuxisms, obviously. But what Linuxisms does s6 have? > The skalibs library used by s6 to calculate the deadlines should use clock_gettime(CLOCK_MONOTONIC) on FreeBSD and as such shouldn't be affected by changes to the wall clock. I'm currently working on a FreeBSD only potential init replacement as well just without the mandatory per service supervisor process. The new kqueue EVFILT_PROCDESC filter type in FreeBSD 11 combined with pdfork() should make it really easy to deal child processes in a single unified kevent loop. Forking services could still be handled by a supervisor using procctl(PROC_REAP_ACQUIRE). At the moment I'm fighting with some corner cases in the file descriptor passing code and redesigning the API to work without access to a writable file system. My last API required a writable file system because FreeBSD doesn't support listen()ing on unbound unix domain seqpacket sockets and I don't want to require something like the Linux /run tmpfs. Instead my new API uses socketpair() to create a connected pair of anonymous unix domain sockets for each supervised process. Next I have to find out if fexecve() works at least for fd 0, 1 and 2 without a mounted fdescfs. I want to implement the following features in a single process capable of running as PID 1: - Track service dependencies (want, require, bind, conflict) - Store, Retrieve and close file descriptors. - Spawn and supervise processes in a well defined environment. - Reliable event notification with coalescing. - Bootstrap the system with help from a default service. With those features it should be able to wrap existing rc.d scripts without resorting to polling.
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