kron

Usage
First, you need to create a service account for kron:
# account.yaml
apiVersion: v1
kind: ServiceAccount
metadata:
name: kron
kubectl create -f account.yaml
Then, create a job with labels and annotations for kron:
# job.yaml
apiVersion: batch/v1
kind: Job
metadata:
name: "sample-job"
labels:
kron: true
annotations:
schedule: "@every 5m"
spec:
completions: 0
template:
metadata:
name: "sample-job"
spec:
containers:
- image: alpine:3.4
name: "sample-job"
command: ["echo", "$TEST_VAR"]
env:
- name: TEST_VAR
value: ok
restartPolicy: Never
kubectl create -f job.yaml
Set spec.completions
to 0
if you don't want the job to be executed when you create it.
Finally, run the kron service:
apiVersion: v1
kind: Pod
metadata:
name: kron
spec:
serviceAccountName: kron
containers:
- image: "sabaka/kron"
name: kron
A cron expression represents a set of times, using 6 space-separated fields.
Field name | Mandatory? | Allowed values | Allowed special characters
---------- | ---------- | -------------- | --------------------------
Seconds | Yes | 0-59 | * / , -
Minutes | Yes | 0-59 | * / , -
Hours | Yes | 0-23 | * / , -
Day of month | Yes | 1-31 | * / , - ?
Month | Yes | 1-12 or JAN-DEC | * / , -
Day of week | Yes | 0-6 or SUN-SAT | * / , - ?
Note: Month and Day-of-week field values are case insensitive. "SUN", "Sun",
and "sun" are equally accepted.
Special Characters
Asterisk ( * )
The asterisk indicates that the cron expression will match for all values of the
field; e.g., using an asterisk in the 5th field (month) would indicate every
month.
Slash ( / )
Slashes are used to describe increments of ranges. For example 3-59/15 in the
1st field (minutes) would indicate the 3rd minute of the hour and every 15
minutes thereafter. The form "*\/..." is equivalent to the form "first-last/...",
that is, an increment over the largest possible range of the field. The form
"N/..." is accepted as meaning "N-MAX/...", that is, starting at N, use the
increment until the end of that specific range. It does not wrap around.
Comma ( , )
Commas are used to separate items of a list. For example, using "MON,WED,FRI" in
the 5th field (day of week) would mean Mondays, Wednesdays and Fridays.
Hyphen ( - )
Hyphens are used to define ranges. For example, 9-17 would indicate every
hour between 9am and 5pm inclusive.
Question mark ( ? )
Question mark may be used instead of '*' for leaving either day-of-month or
day-of-week blank.
Predefined schedules
You may use one of several pre-defined schedules in place of a cron expression.
Entry | Description | Equivalent To
----- | ----------- | -------------
@yearly (or @annually) | Run once a year, midnight, Jan. 1st | 0 0 0 1 1 *
@monthly | Run once a month, midnight, first of month | 0 0 0 1 * *
@weekly | Run once a week, midnight on Sunday | 0 0 0 * * 0
@daily (or @midnight) | Run once a day, midnight | 0 0 0 * * *
@hourly | Run once an hour, beginning of hour | 0 0 * * * *
Intervals
You may also schedule a job to execute at fixed intervals. This is supported by
formatting the cron spec like this:
@every <duration>
where "duration" is a string accepted by time.ParseDuration
(http://golang.org/pkg/time/#ParseDuration).
For example, "@every 1h30m10s" would indicate a schedule that activates every
1 hour, 30 minutes, 10 seconds.
Note: The interval does not take the job runtime into account. For example,
if a job takes 3 minutes to run, and it is scheduled to run every 5 minutes,
it will have only 2 minutes of idle time between each run.
Time zones
All interpretation and scheduling is done in the machine's local time zone (as
provided by the Go time package (http://www.golang.org/pkg/time).
Be aware that jobs scheduled during daylight-savings leap-ahead transitions will
not be run!
Development
glide install