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-rw-r--r--Propellor/Property/Cron.hs16
-rw-r--r--debian/changelog2
2 files changed, 14 insertions, 4 deletions
diff --git a/Propellor/Property/Cron.hs b/Propellor/Property/Cron.hs
index 2fa9c87e..d8c072eb 100644
--- a/Propellor/Property/Cron.hs
+++ b/Propellor/Property/Cron.hs
@@ -3,14 +3,19 @@ module Propellor.Property.Cron where
import Propellor
import qualified Propellor.Property.File as File
import qualified Propellor.Property.Apt as Apt
+import Utility.SafeCommand
import Data.Char
type CronTimes = String
--- | Installs a cron job, run as a specificed user, in a particular
---directory. Note that the Desc must be unique, as it is used for the
---cron.d/ filename.
+-- | Installs a cron job, run as a specified user, in a particular
+-- directory. Note that the Desc must be unique, as it is used for the
+-- cron.d/ filename.
+--
+-- Only one instance of the cron job is allowed to run at a time, no matter
+-- how long it runs. This is accomplished using flock locking of the cron
+-- job file.
job :: Desc -> CronTimes -> UserName -> FilePath -> String -> Property
job desc times user cddir command = cronjobfile `File.hasContent`
[ "# Generated by propellor"
@@ -18,11 +23,14 @@ job desc times user cddir command = cronjobfile `File.hasContent`
, "SHELL=/bin/sh"
, "PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin"
, ""
- , times ++ "\t" ++ user ++ "\t" ++ "cd " ++ cddir ++ " && " ++ command
+ , times ++ "\t" ++ user ++ "\t"
+ ++ "flock -n " ++ shellEscape cronjobfile
+ ++ " -c sh -c " ++ shellEscape cmdline
]
`requires` Apt.serviceInstalledRunning "cron"
`describe` ("cronned " ++ desc)
where
+ cmdline = "cd " ++ cddir ++ " && " ++ command
cronjobfile = "/etc/cron.d/" ++ map sanitize desc
sanitize c
| isAlphaNum c = c
diff --git a/debian/changelog b/debian/changelog
index 172ca7ae..e7654a07 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -8,6 +8,8 @@ propellor (0.3.1) UNRELEASED; urgency=medium
* Properties can now be satisfied differently on different operating
systems.
* Standard apt configuration for stable now includes backports.
+ * Cron jobs generated by propellor use flock(1) to avoid multiple
+ instances running at a time.
-- Joey Hess <joeyh@debian.org> Fri, 11 Apr 2014 15:00:11 -0400