[core] Increment ref count when creating an ObjectRef to prevent object from going out of scope#22120
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stephanie-wang merged 16 commits intoray-project:masterfrom Feb 8, 2022
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stephanie-wang
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Feb 4, 2022
| NodeID::FromBinary(rpc_address_.raylet_id())); | ||
| auto status = Put(object, contained_object_ids, *object_id, /*pin_object=*/true); | ||
| if (!status.ok()) { | ||
| reference_counter_->RemoveOwnedObject(*object_id); |
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This is the fix compared to the previous PR (we no longer need the RemoveOwnedObject call because the ref will get deleted when we remove the local ref).
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…ct from going out of scope (ray-project#22120) When a Ray program first creates an ObjectRef (via ray.put or task call), we add it with a ref count of 0 in the C++ backend because the language frontend will increment the initial local ref once we return the allocated ObjectID, then delete the local ref once the ObjectRef goes out of scope. Thus, there is a brief window where the object ref will appear to be out of scope. This can cause problems with async protocols that check whether the object is in scope or not, such as the previous bug fixed in ray-project#19910. Now that we plan to enable lineage reconstruction to automatically recover lost objects, this race condition can also be problematic because we use the ref count to decide whether an object needs to be recovered or not. This PR avoids these race conditions by incrementing the local ref count in the C++ backend when executing ray.put() and task calls. The frontend is then responsible for skipping the initial local ref increment when creating the ObjectRef. This is the same fix used in ray-project#19910, but generalized to all initial ObjectRefs. This is a re-merge for ray-project#21719 with a fix for removing the owned object ref if creation fails.
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Why are these changes needed?
When a Ray program first creates an ObjectRef (via ray.put or task call), we add it with a ref count of 0 in the C++ backend because the language frontend will increment the initial local ref once we return the allocated ObjectID, then delete the local ref once the ObjectRef goes out of scope. Thus, there is a brief window where the object ref will appear to be out of scope.
This can cause problems with async protocols that check whether the object is in scope or not, such as the previous bug fixed in #19910. Now that we plan to enable lineage reconstruction to automatically recover lost objects, this race condition can also be problematic because we use the ref count to decide whether an object needs to be recovered or not.
This PR avoids these race conditions by incrementing the local ref count in the C++ backend when executing ray.put() and task calls. The frontend is then responsible for skipping the initial local ref increment when creating the ObjectRef. This is the same fix used in #19910, but generalized to all initial ObjectRefs.
This is a re-merge for #21719 with a fix for removing the owned object ref if creation fails.