How does Oban Pro burst mode allocate slots across partitions and priorities?

I’m trying to understand how burst: true behaves with partitioned global limits in Oban Pro.

For example, with a queue like:

queue1: [
  local_limit: 5,
  global_limit: [
    allowed: 1,
    burst: true,
    partition: [args: :organization_id]
  ]
]

My understanding is:

• Each partition gets 1 guaranteed slot (allowed: 1)

• With burst: true, partitions can temporarily use additional available slots up to the queue’s available concurrency (local_limit: 5 in this case)

However, I’m confused about how burst slots are actually distributed.

Scenario 1 — Two active partitions

If there are jobs from 2 partitions only, I expected burst mode to greedily utilize all available slots.

But instead of something like:

partition_a = 3
partition_b = 2

I’m seeing behavior closer to:

partition_a = 2
partition_b = 2
1 slot idle

Why is the remaining slot left unused?

Scenario 2 — Three active partitions

Similarly, with 3 partitions active, I expected burst to continue filling remaining capacity, but it seems closer to:

partition_a = 1
partition_b = 1
partition_c = 1
2 slots idle

instead of using the full queue capacity.

Does burst mode not greedily allocate all available slots?

Scenario 3 — Priority interaction

I also noticed that priority doesn’t seem to affect burst allocation the way I expected.

Suppose:

• Partition A jobs have priority 0

• Partition B jobs have priority 0

• Partition C jobs have priority 1

I expected all burst capacity to be consumed by priority 0 jobs first before any priority 1 jobs ran.

Instead, it seems like slots are distributed across all partitions regardless of priority, e.g.:

A = 1
B = 1
C = 1

Why does burst allocation behave this way?

How exactly does Oban Pro decide:

1. Whether additional burst slots should be used

2. Which partition receives them

3. Whether priorities are considered before burst distribution

4. Why queue capacity may remain idle even when runnable jobs exist