Frequently Asked Questions

This FAQ page compiles questions frequently asked by our end users to provide informative and concise answers. If the following sections do not address your concerns, please feel free to open an issue or post it to discussions.

  1. What are the objects in vineyard?

A global object is composed of multiple local objects distributed across the cluster, with each local object stored in a single vineyard daemon (ensuring that a local object can always fit into the memory of a single machine).

These local objects represent partitions of the global object (e.g., partitioned dataframes within a large dataframe, graph fragments within a vast graph). Generally, a global object serves as an abstraction for the input or output of a parallel-processing workload, while a local object corresponds to the input or output of an individual worker within that workload.

  1. Can multiple readers access the same data simultaneously in vineyard?

Absolutely. Vineyard stores objects as immutable entities, which are shared among readers’ processes through memory mapping. This ensures safe and concurrent access to objects by multiple readers without any conflicts.

  1. How can I launch a cluster with multiple vineyardd instances?

A vineyard daemon server represents a single vineyard instance within a vineyard cluster. To initiate a vineyard cluster, simply start the vineyardd process on all the machines within the cluster, ensuring that these vineyard instances can register with the same etcd_endpoint. The default value for etcd_endpoint is http://127.0.0.1:2379, and if the etcd servers are not already running on the cluster, vineyard will automatically launch the etcd_endpoint.

For additional parameter settings, refer to the help documentation by running python3 -m vineyard --help.

  1. Is Kubernetes a necessity for vineyard?

No, Kubernetes is not a necessity for vineyard. However, deploying vineyard on Kubernetes allows users to benefit from the flexible resource management offered by cloud-native deployments for their application workloads. Additionally, the scheduler plugin assists in co-locating worker pods with the data for improved data-work alignment.

  1. How does vineyard achieve IPC and memory sharing (i.e., zero-copy sharing) on Kubernetes?

Inter-process memory sharing can be challenging in Kubernetes, but it is achievable. When deployed on Kubernetes, vineyard exposes its UNIX-domain socket as a PersistentVolume. This volume can be mounted into the job’s pod, allowing the socket to be used for IPC connections to the vineyard daemon. Memory sharing is accomplished by mounting a volume of medium Memory into both the vineyard daemon’s pod and the job’s pod.

  1. How does vineyard’s stream differ from similar systems, such as Kafka?

Vineyard’s stream is an abstraction of a sequence of objects, where each object typically represents a small portion of the entire object (e.g., a mini-batch of a tensor). This abstraction is designed to support cross-engine pipelining between consecutive workers in a data analytics pipeline (e.g., a dataframe engine generating training data while the subsequent machine learning engine consumes the data and trains the model simultaneously).

The primary distinction between vineyard’s stream and traditional stream frameworks like Kafka is that data in vineyard’s stream is still abstracted as (high-level) objects and can be consumed in a zero-copy manner, similar to normal objects in vineyard. In contrast, Kafka is designed for stream processing applications and abstracts data as (low-level) messages. Utilizing Kafka in the aforementioned scenario would still incur (de)serialization and memory copy costs.

  1. Does vineyard support accessing remote objects?

Yes, vineyard’s RPC client can access the metadata of an object, regardless of whether the object is local or remote. This capability enables users and internal operators to examine essential information (e.g., chunk axis, size) about an object, assisting in decision-making processes related to object management (e.g., determining the need for repartitioning, planning the next workload).

  1. How does migration work in vineyard? Is it automatically triggered?

Consider a scenario where workload A produces a global object O, and the subsequent workload B consumes O as input. In a Kubernetes cluster with multiple hosts (e.g., h1, h2, h3, h4), if A has two worker pods on h1 and h2, the local objects (i.e., O1 and O2) of O are stored on h1 and h2, respectively.

If the two worker pods of B (i.e., B1 and B2) are placed on h1 and h3, B1 can access O1 locally via memory mapping. However, B2 (on h3) cannot access O2 since it resides on h2. In this situation, a utility program distributed with vineyard in the initContainer of B2 triggers the migration of O2 from h2 to h3, enabling pod B2 to access O2 locally.

Although data migration incurs a cost, the scheduler plugin has been developed to prioritize h2 when launching B2, minimizing the need for migration whenever possible.

  1. What’s the minimal Kubernetes version requirement for vineyard operator?

At present, we only test the vineyard operator based on Kubernetes 1.24.0. So we highly recommend using Kubernetes 1.24.0 or above.

  1. Why the vineyard operator can’t be deployed on Kubernetes?

If you use the helm to deploy the vineyard operator, you may find the vineyard operator can’t be deployed successfully after a long time. In this case, you should check whether the command contains the flag –wait. If so, you should remove the flag –wait and try to install the operator again.

  1. How to connect to the vineyard cluster deployed by the vineyard operator?

There are two ways to connect to the vineyard cluster deployed by the vineyard operator:

  • Through IPC. Create a pod with the specific labels so that the pod can be scheduled to the node where the vineyard cluster is deployed.

  • Through RPC. Connect to the vineyard cluster through the RPC service exposed by the vineyard operator. You could refer to the guide for more details.

  1. Is there a way to install the vineyard cluster on Kubernetes quickly?

To reduce the complexity of the installation, we provide a command line tool to install the vineyard cluster on Kubernetes quickly.