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schedule.ts
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schedule.ts
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import { Construct } from 'constructs';
import { Annotations, Duration } from '../../core';
/**
* Schedule for scheduled event rules
*
* Note that rates cannot be defined in fractions of minutes.
*
* @see https://docs.aws.amazon.com/eventbridge/latest/userguide/scheduled-events.html
*/
export abstract class Schedule {
/**
* Construct a schedule from a literal schedule expression
*
* @param expression The expression to use. Must be in a format that EventBridge will recognize
*/
public static expression(expression: string): Schedule {
return new LiteralSchedule(expression);
}
/**
* Construct a schedule from an interval and a time unit
*
* Rates may be defined with any unit of time, but when converted into minutes, the duration must be a positive whole number of minutes.
*/
public static rate(duration: Duration): Schedule {
if (duration.isUnresolved()) {
const validDurationUnit = ['minute', 'minutes', 'hour', 'hours', 'day', 'days'];
if (validDurationUnit.indexOf(duration.unitLabel()) === -1) {
throw new Error("Allowed units for scheduling are: 'minute', 'minutes', 'hour', 'hours', 'day', 'days'");
}
return new LiteralSchedule(`rate(${duration.formatTokenToNumber()})`);
}
if (duration.toMinutes() === 0) {
throw new Error('Duration cannot be 0');
}
let rate = maybeRate(duration.toDays({ integral: false }), 'day');
if (rate === undefined) { rate = maybeRate(duration.toHours({ integral: false }), 'hour'); }
if (rate === undefined) { rate = makeRate(duration.toMinutes({ integral: true }), 'minute'); }
return new LiteralSchedule(rate);
}
/**
* Create a schedule from a set of cron fields
*/
public static cron(options: CronOptions): Schedule {
if (options.weekDay !== undefined && options.day !== undefined) {
throw new Error('Cannot supply both \'day\' and \'weekDay\', use at most one');
}
const minute = fallback(options.minute, '*');
const hour = fallback(options.hour, '*');
const month = fallback(options.month, '*');
const year = fallback(options.year, '*');
// Weekday defaults to '?' if not supplied. If it is supplied, day must become '?'
const day = fallback(options.day, options.weekDay !== undefined ? '?' : '*');
const weekDay = fallback(options.weekDay, '?');
return new class extends Schedule {
public readonly expressionString: string = `cron(${minute} ${hour} ${day} ${month} ${weekDay} ${year})`;
public _bind(scope: Construct) {
if (!options.minute) {
Annotations.of(scope).addWarningV2('@aws-cdk/aws-events:scheduleWillRunEveryMinute', 'cron: If you don\'t pass \'minute\', by default the event runs every minute. Pass \'minute: \'*\'\' if that\'s what you intend, or \'minute: 0\' to run once per hour instead.');
}
return new LiteralSchedule(this.expressionString);
}
};
}
/**
* Retrieve the expression for this schedule
*/
public abstract readonly expressionString: string;
protected constructor() {}
/**
*
* @internal
*/
public abstract _bind(scope: Construct): void;
}
/**
* Options to configure a cron expression
*
* All fields are strings so you can use complex expressions. Absence of
* a field implies '*' or '?', whichever one is appropriate.
*
* @see https://docs.aws.amazon.com/eventbridge/latest/userguide/scheduled-events.html#cron-expressions
*/
export interface CronOptions {
/**
* The minute to run this rule at
*
* @default - Every minute
*/
readonly minute?: string;
/**
* The hour to run this rule at
*
* @default - Every hour
*/
readonly hour?: string;
/**
* The day of the month to run this rule at
*
* @default - Every day of the month
*/
readonly day?: string;
/**
* The month to run this rule at
*
* @default - Every month
*/
readonly month?: string;
/**
* The year to run this rule at
*
* @default - Every year
*/
readonly year?: string;
/**
* The day of the week to run this rule at
*
* @default - Any day of the week
*/
readonly weekDay?: string;
}
class LiteralSchedule extends Schedule {
constructor(public readonly expressionString: string) {
super();
}
public _bind() {}
}
function fallback<T>(x: T | undefined, def: T): T {
return x ?? def;
}
/**
* Return the rate if the rate is whole number
*/
function maybeRate(interval: number, singular: string) {
if (interval === 0 || !Number.isInteger(interval)) { return undefined; }
return makeRate(interval, singular);
}
/**
* Return 'rate(${interval} ${singular}(s))` for the interval
*/
function makeRate(interval: number, singular: string) {
return interval === 1 ? `rate(1 ${singular})` : `rate(${interval} ${singular}s)`;
}