allocatorimpl: adds a priority assertion to computeAction

This commit adds an assertion to Allocator.ComputeAction to ensure that priority
is never -1 in cases where it shouldn’t be. Normally, ComputeAction returns
action.Priority(), but we sometimes adjust the priority for specific actions
like AllocatorAddVoter, AllocatorRemoveDeadVoter, and AllocatorRemoveVoter. A
priority of -1 is a special case reserved for processing logic to run even if
there’s a priority inversion. If the priority is not -1, the range may be
re-queued to be processed with the correct priority.

Author: wenyihu6

pkg/kv/kvserver/allocator/allocatorimpl/allocator.go

@@ -27,6 +27,7 @@ import (
 	"github.com/cockroachdb/cockroach/pkg/roachpb"
 	"github.com/cockroachdb/cockroach/pkg/settings"
 	"github.com/cockroachdb/cockroach/pkg/settings/cluster"
+	"github.com/cockroachdb/cockroach/pkg/util/buildutil"
 	"github.com/cockroachdb/cockroach/pkg/util/log"
 	"github.com/cockroachdb/cockroach/pkg/util/metric"
 	"github.com/cockroachdb/cockroach/pkg/util/syncutil"
@@ -946,8 +947,21 @@ func (a *Allocator) ComputeAction(
 		return action, action.Priority()
 	}
 
-	return a.computeAction(ctx, storePool, conf, desc.Replicas().VoterDescriptors(),
+	action, priority = a.computeAction(ctx, storePool, conf, desc.Replicas().VoterDescriptors(),
 		desc.Replicas().NonVoterDescriptors())
+	// Ensure that priority is never -1. Typically, computeAction return
+	// action.Priority(), but we sometimes modify the priority for specific
+	// actions like AllocatorAddVoter, AllocatorRemoveDeadVoter, and
+	// AllocatorRemoveVoter. A priority of -1 is a special case, indicating that
+	// the caller expects the processing logic to be invoked even if there's a
+	// priority inversion. If the priority is not -1, the range might be re-queued
+	// to be processed with the correct priority.
+	if priority == -1 && buildutil.CrdbTestBuild {
+		log.Fatalf(ctx, "allocator returned -1 priority for range %s: %v", desc, action)
+	} else {
+		log.Warningf(ctx, "allocator returned -1 priority for range %s: %v", desc, action)
+	}
+	return action, priority
 }
 
 func (a *Allocator) computeAction(