The introduction of the Container Storage Interface (CSI) provides an exciting opportunity to the world of Container Orchestrator (CO) and storage. This document reviews how CSI adds value to REX-Ray, strengthening its position as the leading CO storage management solution.
Note: Before reading this document please take time to review the several REX-Ray/CSI architecture and component types.
This section illustrates the proposed solution for introducing CSI to REX-Ray and libStorage:
- Create a new libStorage interface,
EndpointProvider:
type EndpointProvider interface {
// Close immediately closes all active net.Listeners and any
// connections in state StateNew, StateActive, or StateIdle. For a
// graceful shutdown, use Shutdown.
Close() error
// Serve accepts incoming connections on the Listener l, creating a
// new service goroutine for each.
Serve(l net.Listener) error
// Shutdown gracefully shuts down the server without interrupting any
// active connections. Shutdown works by first closing all open
// listeners, then closing all idle connections, and then waiting
// indefinitely for connections to return to idle and then shut down.
// If the provided context expires before the shutdown is complete,
// then the context's error is returned.
Shutdown(ctx context.Context) error
}- Refactor the libStorage API (HTTP/REST) components into an implementation
of the
EndpointProviderinterface. - Relocate the Docker Volume Driver endpoint from REX-Ray to libStorage
and then refactor the endpoint provider as an implementation of the
EndpointProviderinterface. - Create CSI implementations of the
EndpointProviderinterface:csi.nodecsi.controllercsi.node+controller
- Introduce the following configuration enhancements:
- Use
libstorage.server.endpoints.NAME.typeto specify the endpoint's provider type - Use
libstorage.server.endpoints.NAME.servicesto define which configured storage service(s) an endpoint will expose. Please note that if an endpoint provider is not capable of consuming more than one service the property can be defined as astring, otherwise it would be[]string.
- Use
This section visualizes the proposed changes as two diagrams that represent a centralized architecture with Docker as the CO, without and with CSI support.
The first diagram illustrates the centralized architecture as it is today using Docker as the CO:
The second diagram also outlines the centralized architecture, but this time includes the model as it would appear with the changes required to support CSI described above:
This section lists the supported endpoint provider types:
| Type | Multi-Service Support | Description |
|---|---|---|
libstorage |
✓ | The libStorage API (HTTP/REST) endpoint provider |
docker |
The Docker Volume Driver (HTTP/REST) endpoint provider | |
csi |
The CSI node+controller (gRPC) endpoint provider | |
csi.node |
The CSI node (gRPC) endpoint provider | |
csi.controller |
The CSI controller (gRPC) endpoint provider |
This section estimates the story points for the issues above:
| Issue | Summary | Story Points |
|---|---|---|
#1 |
EndpointProvider interface |
8 |
#2 |
Refactor libStorage w EndpointProvider interface |
21 |
#3 |
Relocate/Refactor Docker Vol Driver | 13 |
#4 |
Create CSI endpoint providers | 21 |
#4 |
Enhance libStorage configuration | 13 |
76 |
