[@aws-cdk/aws-events] Schedule cannot be created from CfnParameter

[alopix]

When trying to use a parameter for the duration of a events Schedule, on synth, an error occurs: "Unable to perform time unit conversion on un-resolved token -1.8881545897087682e+289."

Specifying the duration for e.g. a Lambda timeout works, but not if the Duration is used in a Schedule.rate.

Reproduction Steps

import { Stack, App, Duration, CfnParameter } from '@aws-cdk/core';
import { Rule, Schedule } from '@aws-cdk/aws-events';

const invokeScheduleInMinutes = new CfnParameter(this, 'invokeScheduleInMinutes', {
      type: 'Number',
      description: 'The minutes between scheduled lambda invocations.'
});

new Rule(this, 'Rule', {
      ruleName: `cron`,
      schedule: Schedule.rate(Duration.minutes(invokeScheduleInMinutes.valueAsNumber))
});

Error Log

…/node_modules/@aws-cdk/core/lib/duration.ts:289
    throw new Error(`Unable to perform time unit conversion on un-resolved token ${amount}.`);
          ^
Error: Unable to perform time unit conversion on un-resolved token -1.8881545897087682e+289.
    at convert (…/node_modules/@aws-cdk/core/lib/duration.ts:289:11)
    at Duration.toSeconds (…node_modules/@aws-cdk/core/lib/duration.ts:127:12)
    at Function.rate (…/node_modules/@aws-cdk/aws-events/lib/schedule.ts:20:18)
    at new AppStack (…/infrastructure/stacks/src/AppStack.ts:47:26)
    at Object.<anonymous> (…/infrastructure/stacks/src/app.ts:21:1)
    at Module._compile (internal/modules/cjs/loader.js:1158:30)
    at Module.m._compile (…/node_modules/ts-node/src/index.ts:858:23)
    at Module._extensions..js (internal/modules/cjs/loader.js:1178:10)
    at Object.require.extensions.<computed> [as .ts] (…/node_modules/ts-node/src/index.ts:861:12)
    at Module.load (internal/modules/cjs/loader.js:1002:32)

Environment

• CLI Version : 1.56.0
• Framework Version: 1.56.0
• Node.js Version: v12.16.1
• OS : macOS
• Language (Version): TypeScript 3.9.7

Other

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This is 🐛 Bug Report

[rix0rrr]

As a workaround, use Schedule.expression() for now.

---

For fixing this:

Duration should should have an isUnresolved() method, and Schedule.rate should just render the number in the given unit if the duration is unresolved.

Same for other rate() methods in the library.

[raphael-riel]

For the records, here is a working example for the proposed workaround:

        const rateMinutes = new cdk.CfnParameter(this, "RateMinutes", {
            default: 5,
            description: "...",
            type: "Number",
        });

        new events.Rule(this, "ScheduledFlush", {
            schedule: events.Schedule.expression(`rate(${rateMinutes.value} minutes)`),
            targets: [
                new eventsTargets.LambdaFunction(flushFunction),
            ],
        });

cron(...) expression is also possible. Ref: https://github.com/aws-samples/aws-cdk-examples/blob/master/typescript/lambda-cron/index.ts#L22

[alopix]

Thanks for the workaround suggestions.
This does not solve the problem though. It will work for the schedule, but e.g. a Metric period is still gonna fail the same way, as it requires a resolved Duration value and does not work from a Parameter.

[jumic]

The code in this issue can be used without error in the meanwhile.
It was resolved in PR #13064. This issue is still open because it wasn't referenced correctly in the PR.

@peterwoodworth Could you please close this issue?

[peterwoodworth]

Will do, thank you

[github-actions]

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