Added `OfferConstraints` validity criteria into protobuf comments.
Review: https://reviews.apache.org/r/72898
diff --git a/include/mesos/scheduler/scheduler.proto b/include/mesos/scheduler/scheduler.proto
index f70738c..f70d379 100644
--- a/include/mesos/scheduler/scheduler.proto
+++ b/include/mesos/scheduler/scheduler.proto
@@ -443,6 +443,15 @@
// NOTE: Even if a particular resource matches offer constraints of a
// framework's role, there is still no guarantee that it will ever be offered
// to this role of the framework.
+//
+// NOTE: Each `Group` must contain at least one constraint, and
+// `RoleConstraints` must contain at least one `Group`, otherwise
+// the message is not valid.
+//
+// NOTE: Frameworks are allowed to use default-constructed
+// `OfferConstraints` (instead of not setting the `offer_constraints` field)
+// in the SUBSCRIBE/UPDATE_FRAMEWORK calls to indicate subscription without
+// any offer constraints.
message OfferConstraints {
message RoleConstraints {
message Group {
diff --git a/include/mesos/v1/scheduler/scheduler.proto b/include/mesos/v1/scheduler/scheduler.proto
index 364d2c8..a8596b6 100644
--- a/include/mesos/v1/scheduler/scheduler.proto
+++ b/include/mesos/v1/scheduler/scheduler.proto
@@ -441,6 +441,15 @@
// NOTE: Even if a particular resource matches offer constraints of a
// framework's role, there is still no guarantee that it will ever be offered
// to this role of the framework.
+//
+// NOTE: Each `Group` must contain at least one constraint, and
+// `RoleConstraints` must contain at least one `Group`, otherwise
+// the message is not valid.
+//
+// NOTE: Frameworks are allowed to use default-constructed
+// `OfferConstraints` (instead of not setting the `offer_constraints` field)
+// in the SUBSCRIBE/UPDATE_FRAMEWORK calls to indicate subscription without
+// any offer constraints.
message OfferConstraints {
message RoleConstraints {
message Group {
