Jenkins 有三种类型的构建触发器，如下图：
- Build after other projects are built：在其他项目构建后构建；
- Build periodically：定时构建；
- Poll SCM：定时检查代码更新，如果有更新则构建。
其中“Build periodically”和“Poll SCM”使用的是Cron，帮助文档如下：
This field follows the syntax of cron (with minor differences). Specifically, each line consists of 5 fields separated by TAB or whitespace:
| MINUTE | Minutes within the hour (0–59) |
| HOUR | The hour of the day (0–23) |
| DOM | The day of the month (1–31) |
| MONTH | The month (1–12) |
| DOW | The day of the week (0–7) where 0 and 7 are Sunday. |
To specify multiple values for one field, the following operators are available. In the order of precedence,
*specifies all valid valuesM-Nspecifies a range of valuesM-N/Xor*/Xsteps by intervals of X through the specified range or whole valid rangeA,B,...,Zenumerates multiple values
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.
Beware that for the day of month field, short cycles such as */3 or H/3 will not work consistently near the end of most months, due to variable month lengths. For example, */3 will run on the 1st, 4th, …31st days of a long month, then again the next day of the next month. Hashes are always chosen in the 1-28 range, so H/3 will produce a gap between runs of between 3 and 6 days at the end of a month. (Longer cycles will also have inconsistent lengths but the effect may be relatively less noticeable.)
Empty lines and lines that start with # will be ignored as comments.
In addition, @yearly, @annually, @monthly, @weekly, @daily, @midnight, and @hourly are supported as convenient aliases. These use the hash system for automatic balancing. For example, @hourly is the same as H * * * * and could mean at any time during the hour. @midnight actually means some time between 12:00 AM and 2:59 AM.
Examples:
1 # every fifteen minutes (perhaps at :07, :22, :37, :52) 2 H/15 * * * * 3 # every ten minutes in the first half of every hour (three times, perhaps at :04, :14, :24) 4 H(0-29)/10 * * * * 5 # once every two hours every weekday (perhaps at 10:38 AM, 12:38 PM, 2:38 PM, 4:38 PM) 6 H 9-16/2 * * 1-5 7 # once a day on the 1st and 15th of every month except December 8 H H 1,15 1-11 *