When setting up how Jenkins shoul pull changes from subversion
I tried checked Poll SCM and set schedule to 5 * * * *, I get the following warning
Spread load evenly by using ‘H * * * *’ rather than ‘5 * * * *’
I'm not sure what H means in this context and why I should use that.
H stands for Hash
To allow periodically scheduled tasks to produce even load on the
system, the symbol H (for “hash”) should be used wherever possible.
For example, using 0 0 * * * for a dozen daily jobs will cause a large
spike at midnight. In contrast, using H H * * * would still execute
each job once a day, but not all at the same time, better using
limited resources.
Click on the question-mark beside your schedule specification.
It says there:
To allow periodically scheduled tasks to produce even load on the
system, the symbol H (for “hash”) should be used wherever possible.
For example, using 0 0 * * * for a dozen daily jobs will cause a large
spike at midnight. In contrast, using H H * * * would still execute
each job once a day, but not all at the same time, better using
limited resources.
Also in the documentation worth noting is that:
The H symbol can be used with a range. For example, H H(0-7) * * * means some time between 12:00 AM (midnight) to 7:59 AM. You can also use step intervals with H, with or without ranges.
The H symbol can be thought of as a random value over a range, but it actually is a hash of the job name, not a random function, so that the value remains stable for any given project.
Related
I am trying to understand when this trigger runs in Jenkins groovy script. Seems to me that Jenkins groovy script has some DSL for cron. Does anyone know when this cron job is triggered?
triggers {
cron('H 5 * * 7')
}
In H 5 * * 7 the H means hash. You can have digit in the first place, but H allows to distribute the load better.
H = minute when less load is expected, Jenkins will propose it the first time, after that it will stay more or less the same, if there are available agents to handle it.
5 = hour,
* = any value (every day),
* = any value (every month),
7 = 7th day of week (Sunday).
Reference:
Spread load evenly by using ‘H * * * *’ rather than ‘5 * * * *’
You can test it using the CRONTab tester.
This means to start at 5:00 on every sunday
https://crontab.guru/#0_5_*_*_7
I'm trying to understand the way to scheduling a job
H 6 * * * -> this launch every day at morning
So How can I launch 3 builds every morning ?
Thanks
You can click on the "?" in the GUI to get this help:
To specify multiple values for one field, the following operators are available. In the order of precedence,
- * specifies all valid values
- M-N specifies a range of values
- M-N/X or */X steps by intervals of X through the specified range or whole valid range
- A,B,...,Z enumerates multiple values
With this help you should use
H 6-7/3 * * *
to get three build between 6 AM and 7 AM.
I have some parameterized build in Jenkins with several Active Choice Reactive Parameters: par1, par2.
par1 is defined by combo, and par2 value depends on par1:
switch (par1) {
case 'value1': return 'test1'
case 'value2': return 'test2'
default: return 'test'
}
It works fine for manual trigger, but fails if I try to use parameterized shedule trigger:
H * * * * %par1=value1
Is it possible to solve this issue somehow?
Your input for periodic is supposed to run per hour (1).
Change this H * * * * %par1=value1 to either * * * * * every minute OR H/1 * * * * (1 hour) or H/2 * * * * (every 2 minutes). yea, it's kind of confusing when you use 1 it makes it one hour vs 1 minute (with H/1)
Also, make sure your par2 (Groovy code section within Active choice reactive parameter) is handling cases where par1 is not just a single value (test1) i.e. it can be test1,test2,test3,... when a user would have selected multiple values for par2 parameter (if it is a Multiple Select type).
How can I set Jenkins to run a job at a particular time?
Like if I'd like to set it to 8:30am every weekday and this is what I could do
H 7 * * 1-5
this randomly picks up 7:35am as running time.
H is a pseudo-random number, based on the hash of the jobname.
When you configured:
H 7
you are telling it:
At 7 o'clock, at random minute, but that same minute very time
Here is the help directly from Jenkins (just click the ? icon)
To allow periodically scheduled tasks to produce even load on the system, the symbol H (for “hash”) should be used wherever possible. For example, using 0 0 * * * for a dozen daily jobs will cause a large spike at midnight. In contrast, using H H * * * would still execute each job once a day, but not all at the same time, better using limited resources.
The H symbol can be used with a range. For example, H H(0-7) * * * means some time between 12:00 AM (midnight) to 7:59 AM. You can also use step intervals with H, with or without ranges.
The H symbol can be thought of as a random value over a range, but it actually is a hash of the job name, not a random function, so that the value remains stable for any given project
If you want it at 8:30 every weekday, then you must specify just that:
30 8 * * 1-5
Take a look at http://www.cronmaker.com/
0 30 8 ? * MON,TUE,WED,THU,FRI *
30 8 * * 1-5
This would start at 8:30am Mon-Fri.
0 and 7 are Sundays.
Not sure what the H does but I am assuming it takes the lower case hex of h and applies 68 which is 35 in decimal... lol. Don't do that.
Following this format:
Minute Hour DayOfMonth DayOfWeek Day
It picks that time because you told it that it can, as imagine you already know:
minute, hour, day of month, month, day of week.
Now you have user H which allows Jenkins to pick at random. So you have told it to run between 7-8 every week day.
Change this to:
30 8 * * 1-5
Hope this helps!
A build that takes about three hours to complete needs to be scheduled for nightly building outside office hours: not sooner than 22:00 and not later than 3:59 next day.
I'd also like to use the "H symbol" to avoid collision with future nightly builds. From in-line help in Jenkins:
To allow periodically scheduled tasks to produce even load on the system, the symbol H (for “hash”) should be used wherever possible. For example, using 0 0 * * * for a dozen daily jobs will cause a large spike at midnight. In contrast, using H H * * * would still execute each job once a day, but not all at the same time, better using limited resources.
(How) can I schedule this using Jenkins? What I've tried was all considered invalid by Jenkins:
H H(22,23,0,1,2,3) * * *
Invalid input: "H H(22,23,0,1,2,3) * * *": line 1:7: expecting "-", found ','
H H22,23,0,1,2,3 * * *
Invalid input: "H H22,23,0,1,2,3 * * *": line 1:4: unexpected token: 22
H H(22-3) * * *
Invalid input: "H H(22-3) * * *": line 1:9: 1 is an invalid value. Must be within 1
and -18
Is it possible to achieve this without using plug-ins?
I think the closest you will get is to use:
H H(0-3) * * * This will run at some point between 0:00 and 3:59
#midnight This will run at some point between 0:00 and 2:59
The H(4-8) construct only works if the second items is larger then the first.
But you might as well fill in the hour yourself. Jenkins actually never changes the hour the jobs runs once it is set. It will basically create some random hour once you save the job and always run the job at that particular time.
Of course, you can also file a bug report or feature request that you should be able to specify this as H(22-3) or better, fix the code and submit a patch ;)
There is no direct support to write the expression like this, but since there is timezone support (now), you can work around this.
# DONT COPY PASTE - THIS DOESNT WORK!
# This is what we would like to write, but is not supported
H H(22-3) * * *
Above expression means we want to build somewhen between 22 PM and 3 AM, this is a 5 hour period, so we could write:
# Assuming we're in GMT+2 we can just shift the timezone
# so 22-03 becomes 10-15 wich is 12 hours earlier so the
# timezone is GMT-10
TZ=Etc/GMT-10
H H(10-15) * * *
I found this workaround in the comments of JENKINS-18313
UPDATE:
There is currently a bug JENKINS-57702 and the timezone GMT-XX is not evaluated correctly. A workaround is to use a equivalent timezone, in this example the one for Hawaii:
TZ=US/Hawaii
H H(10-15) * * *