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REX-Ray+CSI: Once more unto the breach
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README.md

REX-Ray+CSI: Once more unto the breach

This document outlines the roadmap for supporting CSI with libStorage and REX-Ray:

Release Description
R1 Initial CSI compatibility
R2 CNCF-ready
R3 Reference CSI implementation

R1 - Initial CSI compatibility

The first release will support both CSI architectures: centralized and decentralized, as well as the hybrid model necessary to satisfy Mesos. Many thanks to @codenrhoden for providing the illustrations!

Arch Diagram
Centralized
Decentralized
Hybrid

Currently the only analogue to the CSI centralized model is K8s where there is a CO master. Docker and Mesos both function in a decentralized model with the libStorage API controller providing optional centralization.

Work Summary Story Points
#1 New REX-Ray module for CSI Ident+Node+Controller Services 21
21

R2 - CNCF-ready

The second release represents a project ready to donate to the CNCF as the default implementation of CSI. The primary feature of this release will be support for out-of-tree drivers via Go plug-ins, making it trivial to deliver CSI compatibility for a given storage platform via REX-Ray.

The diagrams for R2 do not change in any significant way from R1 and will not be repeated. While there is now support for Go plug-ins and the executor will be deprecated, the absence of distributed configuration support means a central libStorage API controller is still required in order to provide single, centralized configuration for storage platforms such as ScaleIO.

Work Summary Story Points
#1 Convert existing drivers into plug-ins 40
#2 Deprecate libStorage executor 21
#3 Update build process to account for plug-ins 21
82

R3 - Reference implementation

Rounding out the roadmap is R3, the release that transforms REX-Ray from a program that embeds the libStorage API into the reference implementation of CSI. This release introduces support for distributed configuration via one or more well-known providers such as Etcd or abstraction libraries like Docker's libkv.

Arch Diagram
Centralized
Decentralized
Hybrid This release no longer includes the hybrid model as the reasons for such a design have been rendered moot by the introduction of distributed configuration support. Please be aware that the Decentralized model below is applicable to both Docker and Mesos.

The introduction of distributed configuration support will also sunset the libStorage API and complete the transformation of REX-Ray into a reference implementation of the CSI specification.

Work Summary Story Points
#1 Distributed configuration support 40
#2 Relocate CSI endpoint from REX-Ray to libStorage 20
60
Raw
r1-c.puml
@startuml
database storage [
Backend
Storage
<U+0020><U+0020><U+0020><U+0020>API
]
rectangle "k8s Master" as knode1 {
frame "k8s" as knode1k {
component "kube-controller-manager" as knode1kd
}
frame "REX-Ray" as knode1rr {
component knode1csi [
**CSI Controller**
---
libStorage Client
]
component "libS Server" as knode1lss
}
knode1kd <-> knode1csi: gRPC
knode1csi <-> knode1lss: HTTP(s)\nJSON
}
rectangle "k8s Minion" as knode2 {
frame "k8s" as knode2k {
component "kubelet" as knode2kd
}
frame "REX-Ray" as knode2rr {
component knode2csi [
**CSI Node**
---
libStorage Client
]
}
knode2kd <-> knode2csi: gRPC
knode2csi <-> knode1lss: HTTP(s)\nJSON
}
knode1lss -> storage
knode1 -[hidden]> storage
storage -[hidden]> knode2
storage -[hidden]> knode2csi
@enduml
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r1-d.puml
@startuml
database storage [
Backend
Storage
<U+0020><U+0020><U+0020><U+0020>API
]
rectangle "Docker Node 1" as dnode1 {
frame "Docker" as dnode1d {
component "dockerd" as dnode1dd
}
frame "REX-Ray" as dnode1rr {
component dnode1csi [
**CSI Node+Controller**
---
libStorage Client
]
component "libS Server" as dnode1lss
}
dnode1dd <-> dnode1csi: gRPC
dnode1csi <-> dnode1lss: HTTP(s)\nJSON
}
rectangle "Docker Node 2" as dnode2 {
frame "Docker" as dnode2d {
component "dockerd" as dnode2dd
}
frame "REX-Ray" as dnode2rr {
component dnode2csi [
**CSI Node+Controller**
---
libStorage Client
]
component "libS Server" as dnode2lss
}
dnode2dd <-> dnode2csi: gRPC
dnode2csi <-> dnode2lss: HTTP(s)\nJSON
}
storage <-> dnode1lss
storage <-> dnode2lss
@enduml
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@startuml
database storage [
Backend
Storage
<U+0020><U+0020><U+0020><U+0020>API
]
rectangle "Docker Node 1" as dnode1 {
frame "Docker" as dnode1d {
component "dockerd" as dnode1dd
}
frame "REX-Ray" as dnode1rr {
component dnode1csi [
**CSI Node+Controller**
- - -
libStorage Client
]
component "libS Server" as dnode1lss
}
dnode1dd <-> dnode1csi: gRPC
dnode1csi <-> dnode1lss: HTTP(s)\nJSON
}
rectangle "Docker Node 2" as dnode2 {
frame "Docker" as dnode2d {
component "dockerd" as dnode2dd
}
frame "REX-Ray" as dnode2rr {
component dnode2csi [
**CSI Node+Controller**
- - -
libStorage Client
]
component "libS Server" as dnode2lss
}
dnode2dd <-> dnode2csi: gRPC
dnode2csi <-> dnode2lss: HTTP(s)\nJSON
}
storage <-> dnode1lss
storage <-> dnode2lss
@enduml
PlantUML version 1.2017.13(Wed May 10 11:52:33 CDT 2017)
(GPL source distribution)
Java Runtime: Java(TM) SE Runtime Environment
JVM: Java HotSpot(TM) 64-Bit Server VM
Java Version: 1.8.0_20-b26
Operating System: Mac OS X
OS Version: 10.12.5
Default Encoding: UTF-8
Language: en
Country: US
--></g></svg>
Raw
r1-h.puml
@startuml
database storage [
Backend
Storage
<U+0020><U+0020><U+0020><U+0020>API
]
rectangle "Mesos Node 1" as mnode1 {
frame "Mesos" as mnode1m {
component "mesosd" as mnode1md
}
frame "REX-Ray" as mnode1rr {
component mnode1csi [
**CSI Node+Controller**
---
libStorage Client
]
component "libS Server" as mnode1lss
}
mnode1md <-> mnode1csi: gRPC
mnode1csi <-> mnode1lss: HTTP(s)\nJSON
}
rectangle "Mesos Node 2" as mnode2 {
frame "Mesos" as mnode2m {
component "mesosd" as mnode2md
}
frame "REX-Ray" as mnode2rr {
component mnode2csi [
**CSI Node+Controller**
---
libStorage Client
]
}
mnode2md <-> mnode2csi: gRPC
mnode2csi <-> mnode1lss: HTTP(s)\nJSON
}
mnode1lss -> storage
mnode1 -[hidden]> storage
storage -[hidden]> mnode2
storage -[hidden]> mnode2csi
@enduml
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r3-c.puml
@startuml
database storage [
Backend
Storage
<U+0020><U+0020><U+0020><U+0020>API
]
rectangle "k8s Master" as knode1 {
frame "k8s" as knode1k {
component "kube-controller-manager" as knode1kd
}
frame "REX-Ray" as knode1rr {
component "CSI Controller" as knode1csi
}
knode1kd <-> knode1csi: gRPC
}
rectangle "k8s Minion" as knode2 {
frame "k8s" as knode2k {
component "kubelet" as knode2kd
}
frame "REX-Ray" as knode2rr {
component "CSI Node" as knode2csi
}
knode2kd <-> knode2csi: gRPC
}
knode1csi -> storage
knode2csi -> storage
@enduml
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r3-d.puml
@startuml
database storage [
Backend
Storage
<U+0020><U+0020><U+0020><U+0020>API
]
rectangle "Docker Node 1" as dnode1 {
frame "Docker" as dnode1d {
component "dockerd" as dnode1dd
}
frame "REX-Ray" as dnode1rr {
component "CSI Node+Controller" as dnode1csi
}
dnode1dd <-> dnode1csi: gRPC
}
rectangle "Docker Node 2" as dnode2 {
frame "Docker" as dnode2d {
component "dockerd" as dnode2dd
}
frame "REX-Ray" as dnode2rr {
component "CSI Node+Controller" as dnode2csi
}
dnode2dd <-> dnode2csi: gRPC
}
dnode1csi -> storage
dnode2csi -> storage
@enduml
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