2 files changed, 26 insertions, 0 deletions
diff --git a/storageapi/src/vespa/storageapi/messageapi/storagemessage.cpp b/storageapi/src/vespa/storageapi/messageapi/storagemessage.cpp
index f970091f695..3413feeeeab 100644
--- a/storageapi/src/vespa/storageapi/messageapi/storagemessage.cpp
+++ b/storageapi/src/vespa/storageapi/messageapi/storagemessage.cpp
@@ -302,4 +302,14 @@ StorageMessage::getSummary() const {
     return toString();
 }
 
+const char* to_string(LockingRequirements req) noexcept {
+    switch (req) {
+    case LockingRequirements::Exclusive:
+        return "Exclusive";
+    case LockingRequirements::Shared:
+        return "Shared";
+    }
+    assert(false);
+}
+
 }
diff --git a/storageapi/src/vespa/storageapi/messageapi/storagemessage.h b/storageapi/src/vespa/storageapi/messageapi/storagemessage.h
index dadb68c644d..90261c2b9b1 100644
--- a/storageapi/src/vespa/storageapi/messageapi/storagemessage.h
+++ b/storageapi/src/vespa/storageapi/messageapi/storagemessage.h
@@ -306,6 +306,18 @@ struct TransportContext {
     virtual ~TransportContext() = 0;
 };
 
+enum class LockingRequirements : uint8_t {
+    // Operations with exclusive locking can only be executed iff no other
+    // exclusive or shared locks are taken for its bucket.
+    Exclusive = 0,
+    // Operations with shared locking can only be executed iff no exclusive
+    // lock is taken for its bucket. Should only be used for read-only operations
+    // that cannot mutate a bucket's state.
+    Shared
+};
+
+const char* to_string(LockingRequirements req) noexcept;
+
 class StorageMessage : public vespalib::Printable
 {
     friend class StorageMessageTest; // Used for testing only
@@ -421,6 +433,10 @@ public:
     virtual document::Bucket getBucket() const { return getDummyBucket(); }
     document::BucketId getBucketId() const { return getBucket().getBucketId(); }
     virtual bool hasSingleBucketId() const { return false; }
+    virtual LockingRequirements lockingRequirements() const noexcept {
+        // Safe default: assume exclusive locking is required.
+        return LockingRequirements::Exclusive;
+    }
 };
 
 }