cron resource¶
Use the cron resource to manage cron entries for time-based job scheduling.
Warning
The cron resource should only be used to modify an entry in a crontab file. The cron_d
resource directly manages cron.d files. This resource ships in Chef 14.4 or later and can also be found in the cron cookbook) for previous chef-client releases.
Syntax¶
A cron resource block manages cron entries. For example, to get a weekly cookbook report from the Chef Supermarket:
cron 'cookbooks_report' do
action :create
minute '0'
hour '0'
weekday '1'
user 'getchef'
mailto 'sysadmin@example.com'
home '/srv/supermarket/shared/system'
command %W{
cd /srv/supermarket/current &&
env RUBYLIB="/srv/supermarket/current/lib"
RAILS_ASSET_ID=`git rev-parse HEAD` RAILS_ENV="#{rails_env}"
bundle exec rake cookbooks_report
}.join(' ')
end
The full syntax for all of the properties that are available to the cron resource is:
cron 'name' do
command String
day
environment Hash
home String
hour
mailto String
minute
month
path String
shell String
time Symbol
user String # default value: root
weekday
action Symbol # defaults to :create if not specified
end
where:
cron
is the resource.name
is the name given to the resource block.action
identifies which steps the chef-client will take to bring the node into the desired state.command
,day
,environment
,home
,hour
,mailto
,minute
,month
,path
,shell
,time
,user
, andweekday
are the properties available to this resource.
Actions¶
The cron resource has the following actions:
:create
- Default. Create an entry in a cron table file (crontab). If an entry already exists (but does not match), update that entry to match.
:delete
- Delete an entry from a cron table file (crontab).
:nothing
- Define this resource block to do nothing until notified by another resource to take action. When this resource is notified, this resource block is either run immediately or it is queued up to be run at the end of the Chef Client run.
Note
Chef can only reliably manage crontab entries that it creates. To remove existing system entries we may use execute resource with a guard like:
execute "remove foo_daemon from crontab" do
command "sed -i '/foo_daemon/d' /etc/crontab"
only_if "grep 'foo_daemon' /etc/crontab 2>&1 >/dev/null"
end
Properties¶
The cron resource has the following properties:
command
Ruby Type: String
The command to be run, or the path to a file that contains the command to be run.
Some examples:
command if [ -x /usr/share/mdadm/checkarray ] && [ $(date +\%d) -le 7 ]; then /usr/share/mdadm/checkarray --cron --all --idle --quiet; fi
and:
command %w{ cd /srv/opscode-community-site/current && env RUBYLIB="/srv/opscode-community-site/current/lib" RAILS_ASSET_ID=`git rev-parse HEAD` RAILS_ENV="#{rails_env}" bundle exec rake cookbooks_report }.join(' ')
and:
command "/srv/app/scripts/daily_report"
day
Ruby Type: String | Default Value:
*
The day of month at which the cron entry should run (1 - 31).
environment
Ruby Type: Hash
A Hash of environment variables in the form of
({"ENV_VARIABLE" => "VALUE"})
. (These variables must exist for a command to be run successfully.)home
Ruby Type: String
Set the
HOME
environment variable.hour
Ruby Type: String | Default Value:
*
The hour at which the cron entry is to run (0 - 23).
ignore_failure
Ruby Type: true, false | Default Value:
false
Continue running a recipe if a resource fails for any reason.
mailto
Ruby Type: String
Set the
MAILTO
environment variable.minute
Ruby Type: String | Default Value:
*
The minute at which the cron entry should run (0 - 59).
month
Ruby Type: String | Default Value:
*
The month in the year on which a cron entry is to run (1 - 12).
notifies
Ruby Type: Symbol, ‘Chef::Resource[String]’
A resource may notify another resource to take action when its state changes. Specify a
'resource[name]'
, the:action
that resource should take, and then the:timer
for that action. A resource may notify more than one resource; use anotifies
statement for each resource to be notified.A timer specifies the point during the Chef Client run at which a notification is run. The following timers are available:
:before
- Specifies that the action on a notified resource should be run before processing the resource block in which the notification is located.
:delayed
- Default. Specifies that a notification should be queued up, and then executed at the end of the Chef Client run.
:immediate
,:immediately
- Specifies that a notification should be run immediately, per resource notified.
The syntax for
notifies
is:notifies :action, 'resource[name]', :timer
path
Ruby Type: String
Set the
PATH
environment variable.retries
Ruby Type: Integer | Default Value:
0
The number of times to catch exceptions and retry the resource.
retry_delay
Ruby Type: Integer | Default Value:
2
The retry delay (in seconds).
shell
Ruby Type: String
Set the
SHELL
environment variable.subscribes
Ruby Type: Symbol, ‘Chef::Resource[String]’
A resource may listen to another resource, and then take action if the state of the resource being listened to changes. Specify a
'resource[name]'
, the:action
to be taken, and then the:timer
for that action.Note that
subscribes
does not apply the specified action to the resource that it listens to - for example:file '/etc/nginx/ssl/example.crt' do mode '0600' owner 'root' end service 'nginx' do subscribes :reload, 'file[/etc/nginx/ssl/example.crt]', :immediately end
In this case the
subscribes
property reloads thenginx
service whenever its certificate file, located under/etc/nginx/ssl/example.crt
, is updated.subscribes
does not make any changes to the certificate file itself, it merely listens for a change to the file, and executes the:reload
action for its resource (in this examplenginx
) when a change is detected.A timer specifies the point during the Chef Client run at which a notification is run. The following timers are available:
:before
- Specifies that the action on a notified resource should be run before processing the resource block in which the notification is located.
:delayed
- Default. Specifies that a notification should be queued up, and then executed at the end of the Chef Client run.
:immediate
,:immediately
- Specifies that a notification should be run immediately, per resource notified.
The syntax for
subscribes
is:subscribes :action, 'resource[name]', :timer
time
Ruby Type: Symbol
A time interval. Possible values:
:annually
,:daily
,:hourly
,:midnight
,:monthly
,:reboot
,:weekly
, or:yearly
.user
Ruby Type: String | Default Value:
root
This attribute is not applicable on the AIX platform. The name of the user that runs the command. If the
user
property is changed, the originaluser
for the crontab program continues to run until that crontab program is deleted.weekday
Ruby Type: String | Default Value:
*
The day of the week on which this entry is to run (0 - 6), where Sunday = 0.
Examples¶
The following examples demonstrate various approaches for using resources in recipes:
Run a program at a specified interval
cron 'noop' do
hour '5'
minute '0'
command '/bin/true'
end
Run an entry if a folder exists
cron 'ganglia_tomcat_thread_max' do
command "/usr/bin/gmetric
-n 'tomcat threads max'
-t uint32
-v '/usr/local/bin/tomcat-stat
--thread-max'"
only_if do File.exist?('/home/jboss') end
end
Run every Saturday, 8:00 AM
The following example shows a schedule that will run every hour at 8:00 each Saturday morning, and will then send an email to “admin@example.com” after each run.
cron 'name_of_cron_entry' do
minute '0'
hour '8'
weekday '6'
mailto 'admin@example.com'
action :create
end
Run only in November
The following example shows a schedule that will run at 8:00 PM, every weekday (Monday through Friday), but only in November:
cron 'name_of_cron_entry' do
minute '0'
hour '20'
day '*'
month '11'
weekday '1-5'
action :create
end