Configure job time and date - E-MapReduce - Alibaba Cloud Documentation Center

When you edit a job, you can set time variable wildcards in the job parameters.

Variable wildcard format

E-MapReduce supports variable wildcards in the format of ${dateexpr-1d} or ${dateexpr-1h}. In these formats, dateexpr represents a standard time format expression. The following table describes the format specifiers.

Important The time format specifiers are case-sensitive.

Format	Description
yyyy	The year as a four-digit number.
MM	The month as a two-digit number (01-12).
dd	The day of the month as a two-digit number (01-31).
HH	The hour in 24-hour format (00-23). Use hh for 12-hour format.
mm	The minute as a two-digit number (00-59).
ss	The second as a two-digit number (00-59).

A time variable can be any combination of time specifiers that includes yyyy. You can use the plus (+) and minus (-) signs to specify a time offset. For example, if the variable ${yyyy-MM-dd} represents the current date:

One day later: ${yyyyMMdd+1d} or ${yyyy-MM-dd hh:mm:ss+1d}.
Three hours later: ${yyyyMMddHH+3h} or ${yyyy-MM-dd hh:mm:ss+3h}.
Five days earlier: ${yyyyMMdd-5d} or ${yyyy-MM-dd hh:mm:ss-5d}.

For example, assume that the current time is 20160427 12:08:01:

Entering ${yyyyMMdd HH:mm:ss-1d} in the job parameters resolves to 20160426 12:08:01 at runtime. This expression subtracts one day from the current time, maintaining precision to the second.
The expression ${yyyyMMdd-1d} resolves to 20160426 at runtime, which represents the previous day.
The expression ${yyyyMMdd} resolves to 20160427 at runtime, which represents the current date.

Note

Currently, E-MapReduce supports offsets only for days and hours. This means the offset portion of the variable must use the format +Nd, -Nd, +Nh, or -Nh, where N is an integer.
A time variable parameter must start with yyyy, such as ${yyyy-MM}. If you want to extract a specific time component, such as the month, use the following functions in the job content:
- parseDate(<parameter_name>, <time_format>): Converts the specified parameter to a Date object. <parameter_name> is the name of a variable that you set in the Configuration Parameters section. <time_format> is the time format that you used when you set the variable. For example, if you set a variable current_time = ${yyyyMMddHHmmss-1d}, the time format must be set to yyyyMMddHHmmss.
- formatDate(<Date_object>, <time_format>): Formats a Date object into a time string.
Examples:
- Get the hour literal from the current_time variable: ${formatDate(parseDate(current_time, 'yyyyMMddHHmmss'), 'HH')}
- Get the year literal from the current_time variable: ${formatDate(parseDate(current_time, 'yyyyMMddHHmmss'), 'yyyy')}

Procedure

Go to the Projects page in Data Platform.
1. Log in to the E-MapReduce console with your Alibaba Cloud account.
2. In the top navigation bar, select the region and resource group.
3. Click the Data Development tab.
On the Projects page, locate the desired project and click Edit Job in the Actions column.
Configure job settings.
1. On the Edit Job page, select the desired job, and then click Job Settings in the upper-right corner.
2. In the Configuration parameters section, click the icon to add a parameter, and then set the parameter using the variable wildcard format.
  For example, if you add a parameter named dy_date, you can reference this parameter in the job content as ${dy_date}, such as --hiveconf date=${dy_date}.
  The parameter can now be referenced in your job content.