# Scheduled Rules

# Overview

As an event driven system, Rule Engine evaluates conditions when commands are added to or removed from the current window.

To check conditions on a fixed schedule, regardless of incoming commands, use built-in timer metrics which are generated by the database internally.

Metric Name	Frequency
timer_15s	15 seconds.
timer_1m	1 minute.
timer_15m	15 minutes.
timer_1h	1 hour.

By reacting to a timer metric, a rule is evaluated at the specified frequency, for example, every 15 minutes.

# Analyzing Data

When using timer metrics, the current window contains timer samples instead of data to be analyzed. To analyze the data of a separate metric and not the timer metric itself, use database, value, and lookup functions.

Example:

The condition evaluates to true if the average value for temperature series exceeds the threshold.

db_statistic('avg', '1 hour', 'temperature', 'sensor-01') > 50

Example:

The condition evaluates to true if one of the sensors collecting temperature metric no longer performs data inserts.

getEntityCount('temperature', 'now - 1*DAY', 'now - 1*HOUR', '') > 0

# Custom Schedule

To check the rule condition during specific times of the day, refer to the now field in the condition.

now represents current server time as a DateTime object which provides access to calendar properties such as a hour of the day or day of week.

Daily Task Example.

// Runs between 15:00 and 16:00
now.hourOfDay = 15 &&
db_statistic('avg', '1 hour', 'temperature', 'sensor-01') > 50

The above condition is checked once a day, at 15:00, if the metric is set to timer_1h.

Using metric timer_15m, the condition is checked four times a day: 15:00, 15:15, 15:30, and 15:45.

# Examples

# Weekly Task

The condition below is checked 1,440 times each Thursday, at 00:00, 00:01 etc. when using metric timer_1m.

// Runs on Thursdays
now.dayOfWeek = 'Thursday' &&
db_statistic('avg', '1 hour', 'temperature', 'sensor-01') > 50

# Holiday Calendar

The condition below is checked on days that precede a non-working day, such as weekend or observed holiday, in the United States.

// Returns true before non-working days: weekends and observed holidays
now.is_workday('USA') &&
NOT now.add(1, 'day').is_workday('USA')

Typically, this rule is triggered by the database each Friday evening, but fires on Thursday instead when Friday is an observed holiday based on the observed built-in or custom Workday Calendar.

By default the database contains predefined 2018 Workday Calendars for several countries but also supports the addition of custom calendars.

# Previous Alerts

Use the last_open function to compare the time of the most recent OPEN or REPEAT status event for the current window.

// Check if OPEN / REPEAT occured more than 1 day ago
elapsed_minutes(last_open().command_time) > 24*60