Calculating A Consistent Cache-Friendly Expiration Date For Signed-URLs In Lucee 5.3.2.77

test.cfm

<cfscript>

	/**
	* I return the "monthly" bucket for the given date (defaults to now). This helps with
	* expiration dates on signed-URLs that will be consumed as the origin of a CDN pull-
	* through.
	* 
	* @input I am the date being used to calculate the bucket.
	*/
	public date function getMonthlyBucket( date input = now() )
		cachedWithin = "request"
		{

		var inputYear = input.year();
		var inputMonth = input.month();
		var inputDay = input.day();

		// To calculate the bucket for the input date, we need to roll back to the
		// beginning of the month. And then, roll forward one month. This will place the
		// bucket on the 1st of the next month.
		var bucket = createDate( inputYear, inputMonth, 1 ).add( "m", 1 );

		// Rolling forward to the next month will help with consistent in-app URLs, where
		// the URLs are being GENERATED ON EACH REQUEST. However, not all URLs are
		// consumed in-app. Some URLs are consumed externally, such as in an email.
		// Because of this, we may want to roll-forward an ADDITIONAL MONTH if we are
		// close to the end of the current bucket. This way, an email with embedded
		// images that is sent at the END OF THE BUCKET will continue to work for at
		// least two-weeks (roughly) before they expire.
		if ( inputDay > 15 ) {

			bucket = bucket.add( "m", 1 );

		}

		return( bucket );

	}

	// ------------------------------------------------------------------------------- //
	// ------------------------------------------------------------------------------- //

	fromDate = createDate( 2019, 8, 1 );
	
	// Let's examine the bucket calculation over a 50-day period.
	cfloop(
		index = "i",
		from = 0,
		to = 50,
		step = 1
		) {

		loopDate = fromDate.add( "d", i );
		// Get the monthly bucket for the given date. Normally, this would just be
		// assumed to be "now"; but, for the sake of this demo, we're going to provide
		// an explicit test date.
		bucketDate = getMonthlyBucket( loopDate );

		echoLine(
			loopDate.dateFormat( "short" ),
			" => ",
			bucketDate.dateFormat( "short" )
		);

	}

	// ------------------------------------------------------------------------------- //
	// ------------------------------------------------------------------------------- //

	/**
	* I echo each argument, in turn, and then add a line-break at the end.
	*/
	public void function echoLine() {

		arguments.each(
			( value ) => {

				echo( value & " " );

			}
		);

		echo( "<br />" );

	}

</cfscript>