AdjustPoolSize bypasses pool configuration bounds

[He-Pin]

Motivation

Sending AdjustPoolSize to a pool router can grow or shrink the pool beyond configured limits (nr-of-instances, resizer lowerBound/upperBound). The handler directly creates or removes routees without any bounds checking.

Current Behavior

RoutedActorCell.scala:205-213:

case AdjustPoolSize(change: Int) =>
  if (change > 0) {
    val newRoutees = Vector.fill(change)(pool.newRoutee(cell.routeeProps, context))
    cell.addRoutees(newRoutees)
  } else if (change < 0) {
    val currentRoutees = cell.router.routees
    val abandon = currentRoutees.drop(currentRoutees.length + change)
    cell.removeRoutees(abandon, stopChild = true)
  }

• No check against pool.nrOfInstances(system) (initial pool size)
• No check against resizer lowerBound or upperBound
• pool.newRoutee() is just a factory — creates routee with correct dispatcher but no bounds check

Resizer Bounds Bypassed

DefaultResizer.capacity() (Resizer.scala:178-187) does enforce bounds, but it's only called from ResizablePoolCell.resize() — NOT from the AdjustPoolSize handler. Even ResizablePoolActor delegates AdjustPoolSize to super.receive (the unbounded handler).

Test Confirms Unbounded Behavior

RoundRobinSpec.scala:117-120 shows AdjustPoolSize(+4) growing a pool from 3 to 7 (beyond configured size), with no bounds test asserting this is correct.

Expected Behavior

AdjustPoolSize should respect pool configuration bounds. If a resizer is configured, the handler should delegate to the resizer's capacity logic. If no resizer is configured, the handler should at minimum not shrink below 1 or grow beyond a reasonable limit.

Environment

• Pekko Actor (any version)
• RoutedActorCell.scala:205-213

References

None