feat(cloudwatch): CompositeAlarm

[SeekerWing]

• fix Composite Alarm support on CDK #8462

---

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[rix0rrr]

Haven't had a look in detail, will do that Soon(tm) (promise), but first impressions.

I really like where this is going, with some caveats:

• alarm1.toAlarmRule(AlarmState.ALARM): I'd prefer it if you could just write alarm1 here (compound ALARM states seem like they will be the 99% case of uses, why not optimize for it?)

You can do this by making IAlarm extend IAlarmRule.

• new OrAlarmRule(), new AndAlarmRule(): technically, yeah, of course. But I think I'd prefer more discoverable static factory functions instead (friendlier to autocomplete).

Spitballing some alternative syntax here:

new CompositeAlarm(this, 'ComplicatedAlarmCondition', {
  alarmRule: AlarmRule.someOf(
    AlarmRule.allOf(
      alarm1,
      AlarmRule.fromAlarm(alarm2, AlarmState.OK),
      alarm3),
    AlarmRule.not(AlarmRule.fromAlarm(alarm4, AlarmState.INSUFFICIENT_DATA)),
    AlarmRule.fromBoolean(false),
  ),
});

What do you think?

Not entirely sure I'm in love with the AlarmRule.fromAlarm(alarm, STATE) either, but at least it's consistent. I can see the following alternatives:

1. alarm.toAlarmRule(AlarmState.OK)
2. AlarmRule.fromAlarm(alarm, AlarmState.OK)
3. AlarmRule.fromAlarmOk(alarm)

[rix0rrr]

Probably also AlarmRule.fromString("LITERAL STRING HERE"). I'm starting to value escape hatch mechanisms more and more the more feature requests we get 🤣

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[SeekerWing]

I'd prefer it if you could just write alarm1 here

i completely agree, i was unhappy about how that looked too. this is unnecessary verbosity. i think having Alarm implement the IAlarmRule interface will get the necessary brevity.

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[rix0rrr]

Why not just solve the issue by putting @attribute in the docstring?

[SeekerWing]

i tried, it didn't seem to work. it continued to complain about the missing attribute.

[rix0rrr]

You closed a bunch of comments but I don't see a new revision. Missing push? :)

Pull request has been modified.

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