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| author | Daniel Friesel <derf@finalrewind.org> | 2011-07-08 10:34:14 +0200 |
|---|---|---|
| committer | Daniel Friesel <derf@finalrewind.org> | 2011-07-08 10:34:14 +0200 |
| commit | 2663146eae77d28737291d03a23fb8a33363c500 (patch) | |
| tree | 66e7033e29955c200661c0698e02490a064d39d3 | |
| parent | 69be9eb9a39f3bb67c700f9cde3e1a43d7bd276f (diff) | |
Rewrite rationale, add examples
| -rw-r--r-- | src/randsleep.1 | 60 |
1 files changed, 49 insertions, 11 deletions
diff --git a/src/randsleep.1 b/src/randsleep.1 index d051b73..4b2651e 100644 --- a/src/randsleep.1 +++ b/src/randsleep.1 @@ -26,7 +26,7 @@ version 0.0 .Sh DESCRIPTION . .Nm -executes +execs into .Ar command after sleeping for up to .Ar time @@ -44,19 +44,57 @@ will simply return after sleeping. . .Sh RATIONALE . -.Qq sleep $(( RANDOM % 120 )); do_stuff -and similar constructs are frequently used in crontab entries to decrease load -spikes when several entries are executed at the same time. +When executing commands via cron, you can only select the point at which +they're run in minute granularity. Also, you rarely know how many other +commands may be started at the same point. +To avoid load spikes by too many cronjobs running at the same time, it has +become a rather widespread practice to sleep for a random amount of time +.Pq usually something between 0 and 30 minutes at most +before actually doing anything. . .Pp . -However, in certain shells -.Pq such as Cm dash -.Ev $RANDOM -may not be available. -This leads to workarounds involving, for -example, /dev/urandom and cksum. Since repeating the same workarounds over -and over seems somewhat pointless, this tool was created. +Since the snippets responsible for this may, especially if the shell does not +support +.Ev $RANDOM , +become quite long, I decided to write this utility. +It is an extremely simple C program with no additional dependencies, so using +it should not be a problem. +. +. +.Sh EXAMPLES +. +. +.Ss CRONTAB ONE-LINER +. +.Dl */10 * * * * root sleep $(( RANDOM % 120 )); do_stuff with arguments +. +.Pp +. +With +.Nm , +this would look like: +. +.Dl */10 * * * * root randsleep 120 do_stuff with arguments +. +. +.Ss CRONJOB SCRIPT +. +.Dl #!/bin/sh +.Dl if [\& -z \&"$RANDOM\&" ]; then +.Dl RANDOM=$(dd if=/dev/urandom count=1 2> /dev/null | cksum | cut -c\&"1-5\&") +.Dl fi +.Dl sleep $(( RANDOM % 1800 )) +.Dl # actually do something +. +.Pp +. +With +.Nm : +. +.Dl #!/bin/sh +.Dl randsleep 1800 +.Dl # actually do something . . .Sh AUTHOR |