notes on the order of extenders

kubernetes · Jan 7, 2021 · 8f43f44 · 8f43f44
1 parent 4f390cb
commit 8f43f44
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diff --git a/keps/sig-scheduling/1819-scheduler-extender/README.md b/keps/sig-scheduling/1819-scheduler-extender/README.md
@@ -185,6 +185,9 @@ extenders:
   ignorable: false
 ```
 
+Multiple extenders can be configured and will be called sequentially in the
+scheduler framework.
+
 ### Interface
 
 #### Filter
@@ -233,6 +236,15 @@ type ExtenderFilterResult struct {
 
 The "filter" call may prune the set of nodes based on its filter plugins.
 
+Nodes in both `FailedNodesMap` and `FailedAndUnresolvableNodes` are
+unschedulable, except the nodes in the latter will be skipped in preemption
+phase.
+
+When multiple extenders are configured, unschedulable nodes will not be passed
+to subsequent extenders. It's recommended to order the extenders which may
+report `UnschedulableAndUnresolvable` ahead of others. This can improve the
+preemption efficiency.
+
 #### Prioritize
 
 Arguments passed to the `PrioritizeVerb` endpoint on the extender are the set of