lucasbru commented on code in PR #23454:
URL: https://github.com/apache/kafka/pull/23454#discussion_r4025082428
##########
group-coordinator/src/main/java/org/apache/kafka/coordinator/group/streams/AssignmentRefinerImpl.java:
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@@ -547,4 +897,83 @@ record TaskDecisions(
List<TaskGrant> grantedTasks
) {
}
+
+ /**
+ * What a staged migration needs from the budget, which is what the
classification pass sorts them by.
+ */
+ private enum Warming {
+ /** Nothing can warm this migration and no slot may be spent on it. */
+ PARK,
+
+ /** A standby on the target owner itself already warms it, for free. */
+ BORROW,
+
+ /** A warm-up is already restoring for it, and keeps the slot it was
funded with. */
+ KEEP,
+
+ /** It needs a warm-up placed on its target owner, which costs a slot.
*/
+ PLANT
+ }
+
+ /**
+ * A staged migration competing for a warm-up slot, with the parts of the
funding order that can be resolved
+ * ahead of the comparisons.
+ *
+ * @param task
+ * The task being migrated.
+ * @param targetOwner
+ * The member the warm-up task goes on, if this migration is
funded. Always the migration's target
+ * owner, so that the warm-up can be promoted in place once it has
caught up.
+ * @param targetProcessId
+ * The process that member runs in, whose load the funding order
reads and the accounting raises.
+ * @param sourceLoad
+ * The load of the process still running the task, which cannot
change during a funding pass.
+ * @param borrowable
+ * Whether missing out on a slot leaves the migration warmed
anyway, because a standby on a sibling member
+ * of the target owner's process can be borrowed where it sits.
Such a candidate never parks.
+ */
+ private record FundingCandidate(
+ TaskId task,
+ String targetOwner,
+ String targetProcessId,
+ double sourceLoad,
Review Comment:
But the source of one migration can also be the target of another migration
right? It seems that would change the source load.
It may be worth not tracking the source load precisely for algorithmic
simplicity, but the comments look now act like the source load doesn't change
which I don't think is correct?
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