Package: moreutils Version: 0.47 Severity: wishlist I've written a small tool, called splay. It sleeps for a random number of seconds, up to the number given on the command line. It can also seed the random number generator from the host name or the /etc/machine-id file, which allows you to have consistent delays for each host. This is useful to prevent the thundering herd effect network-using tools can have when you have lots of machines running the same script out of cron.
I've attached splay.c, it just needs -lcrypt to link. -- System Information: Debian Release: wheezy/sid APT prefers testing APT policy: (500, 'testing'), (50, 'unstable'), (1, 'experimental') Architecture: amd64 (x86_64) Kernel: Linux 3.4.0 (SMP w/4 CPU cores) Locale: LANG=nb_NO.UTF-8, LC_CTYPE=nb_NO.UTF-8 (charmap=UTF-8) Shell: /bin/sh linked to /bin/dash Versions of packages moreutils depends on: ii libc6 2.13-35 ii libipc-run-perl 0.92-1 ii perl 5.14.2-14 moreutils recommends no packages. Versions of packages moreutils suggests: pn libtime-duration-perl <none> ii libtimedate-perl 1.2000-1 -- no debconf information -- Tollef Fog Heen UNIX is user friendly, it's just picky about who its friends are
/* * splay.c - sleep for up to a defined interval, with the ability to * be consistent per host name or for a given string. * * Copyright © 2012 Tollef Fog Heen <[email protected]> * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * version 2 as published by the Free Software Foundation. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 * USA * */ #define _XOPEN_SOURCE #include <unistd.h> #include <limits.h> #include <errno.h> #include <string.h> #include <stdlib.h> #include <stdio.h> #include <time.h> void usage(char *argv0) { fprintf(stderr, "Usage: %s [-h] [-m] [-s string] delay\n", argv0); exit(EXIT_FAILURE); } int main(int argc, char **argv) { char *hash = NULL; char hostname[HOST_NAME_MAX]; char c; int delay, splay; FILE *f; while ((c = getopt(argc, argv, "hms:")) != -1) { switch (c) { case 'h': gethostname(hostname, HOST_NAME_MAX); hash = hostname; break; case 'm': f = fopen("/etc/machine-id", "r"); if (!f) { fprintf(stderr, "Failed to open /etc/machine-id: %s\n", strerror(errno)); exit(EXIT_FAILURE); } fgets(hostname, HOST_NAME_MAX, f); hash = hostname; break; case 's': hash = optarg; break; default: usage(argv[0]); } } if (optind != argc - 1) { usage(argv[0]); } else { errno = 0; splay = strtol(argv[optind], NULL, 0); /* XXX error handling */ } if (hash) { /* consistent hashing for host name or string given */ char *cs; int v = 0, shift = 0; cs = crypt(hash, hash); while (*cs) { v ^= ((*cs) << CHAR_BIT * shift); shift = (shift + 1) % sizeof v; cs++; } srand(v); } else { srand(time(NULL)); } delay = rand() % splay; sleep(delay); exit(EXIT_SUCCESS); }
