🔨 Controlling Rule Execution Order

How can I control the order in which Slate's automation rules run? I need these three rules to run in a very specific order.
or
I need the rules to run on person records in the order they were queued up.

You can't.

But I really want to. Our Associate Vice President of Importantness said that staff assignments must be true round-robin (except on the second Tuesday of the month, when we want a manual override option).

You really can't.

Slate's rules engine uses a multi-threaded process to evaluate exclusivity groups in parallel across multiple records. In other words, the rules are running at the exact same time on both Person A and Person B, and the results are written to the database in a batch. The results for B cannot depend on the results for A.

Ok, what are our options?

Rules should be written such that the results are idempotent. a = 1 + 1 is idempotent; the result will always be 2. a = a + 1 is not idempotent, as the results change each time it's run.

There's one out, though. Slate's rules execute a second pass if the first pass produces changes, so it's OK to have Rule B depend on Rule A for the same records. It's not OK to introduce a Rule C that depends on Rule B.

Staff Assignments

The most common use case for ordered rule execution (which, as explained above, does not exist) is round-robin staff assignments. While you cannot build a true round-robin assignment system in Slate's rules engine, there are some options:

• You can use "non-deterministic" rules to randomly assign counselors. Like dice rolls, this will not be equal on a daily basis but should be roughly even over weeks or months.
• Find some property of persons that can roughly balance out your staff assignments. A common approach is to split by first letter groupings of names. So, for example, [A-L] goes to Counselor Jasmine and [M-Z] go to Counselor Steve.
• You can build a weighted distribution system that hashes a source of entropy, such as the record's email address, to generate a number 1-100. A user-scoped field can assign each counselor a range of "slots" 1-100 that determine who gets each record. This is very complex to build but allows pseudo-random, weighted distribution. It is deterministic, so the same email address is assigned to the same counselor each time, helping catch duplicates.