Joint Inference
- JIE PU
Motivation
Inference on the edge can get a shorter latency and a higher throughput, and inference on the cloud can get better inference precision. The collaborative inference technology detects hard samples on the edge and sends them to the cloud for inference. In this way, simple samples inference on the edge ensures latency and throughput, while hard samples inference on the cloud improves the overall precision.
Goals
- Joint inference improves the inference precision without significantly reducing the time and throughput.
Proposal
We propose using Kubernetes Custom Resource Definitions (CRDs) to describe the joint inference specification/status and a controller to synchronize these updates between edge and cloud.
Use Cases
User can create a joint inference service with providing a training script, specifying the aggregation algorithm, configuring training hyper parameters, configuring training datasets.
Users can get the joint inference status, including the counts of inference at the edge/cloud.
Design Details
CRD API Group and Version
The JointInferenceService CRD will be namespace-scoped. The tables below summarize the group, kind and API version details for the CRD.
- JointInferenceService
| Field | Description |
|---|---|
| Group | edgeai.io |
| APIVersion | v1alpha1 |
| Kind | JointInferenceService |
Joint inference CRD
Below is the CustomResourceDefinition yaml for JointInferenceService:
apiVersion: apiextensions.k8s.io/v1
kind: CustomResourceDefinition
metadata:
name: jointinferenceservices.edgeai.io
spec:
group: edgeai.io
names:
kind: JointInferenceService
plural: jointinferenceservices
shortNames:
- jointinferenceservice
- jis
scope: Namespaced
versions:
- name: v1alpha1
subresources:
# status enables the status subresource.
status: {}
served: true
storage: true
schema:
openAPIV3Schema:
type: object
properties:
spec:
type: object
properties:
edgeWorker:
type: object
properties:
name:
type: string
model:
type: object
properties:
name:
type: string
nodeName:
type: string
hardExampleAlgorithm:
type: object
properties:
name:
type: string
workerSpec:
type: object
properties:
scriptDir:
type: string
scriptBootFile:
type: string
frameworkType:
type: string
frameworkVersion:
type: string
parameters:
type: array
items:
type: object
properties:
key:
type: string
value:
type: string
cloudWorker:
type: object
properties:
name:
type: string
model:
type: object
properties:
name:
type: string
nodeName:
type: string
workerSpec:
type: object
properties:
scriptDir:
type: string
scriptBootFile:
type: string
frameworkType:
type: string
frameworkVersion:
type: string
parameters:
type: array
items:
type: object
properties:
key:
type: string
value:
type: string
status:
type: object
properties:
conditions:
type: array
items:
type: object
properties:
type:
type: string
status:
type: string
lastProbeTime:
type: string
format: date-time
lastTransitionTime:
type: string
format: date-time
reason:
type: string
message:
type: string
startTime:
type: string
format: date-time
completionTime:
type: string
format: date-time
uploadCount:
type: integer
additionalPrinterColumns:
- name: Age
type: date
jsonPath: .metadata.creationTimestamp
Joint inference type definition
// +genclient
// +k8s:deepcopy-gen:interfaces=k8s.io/apimachinery/pkg/runtime.Object
// JointInferenceService defines the joint inference service crd
type JointInferenceService struct {
metav1.TypeMeta `json:",inline"`
metav1.ObjectMeta `json:"metadata"`
Spec JointInferenceServiceSpec `json:"spec"`
}
// JointInferenceServiceSpec describes the details configuration
type JointInferenceServiceSpec struct {
EdgeWorker EdgeWorker `json:"edgeWorker"`
CloudWorker CloudWorker `json:"cloudWorker"`
}
// EdgeWorker describes the edge worker
type EdgeWorker struct {
Name string `json:"name"`
Model modelRefer `json:"model"`
NodeName string `json:"nodeName"`
HardExampleAlgorithm HardExampleAlgorithm `json:"hardExampleAlgorithm"`
EdgeWorkerSpec CommonWorkerSpec `json:"workerSpec"`
}
// EdgeWorker describes the cloud worker
type CloudWorker struct {
Name string `json:"name"`
Model modelRefer `json:"model"`
NodeName string `json:"nodeName"`
CloudWorkerSpec CommonWorkerSpec `json:"workerSpec"`
}
type modelRefer struct {
Name string `json:"name"`
}
type HardExampleAlgorithm struct {
Name string `json:"name"`
}
type CommonWorkerSpec struct {
ScriptDir string `json:"scriptDir"`
ScriptBootFile string `json:"scriptBootFile"`
FrameworkType string `json:"frameworkType"`
FrameworkVersion string `json:"frameworkVersion"`
Parameters ParaSpec `json:"parameters"`
}
// +k8s:deepcopy-gen:interfaces=k8s.io/apimachinery/pkg/runtime.Object
// JointInferenceServiceList is a list of joint inference services.
type JointInferenceServiceList struct {
metav1.TypeMeta `json:",inline"`
metav1.ListMeta `json:"metadata"`
Items []JointInferenceService `json:"items"`
}
Validation
Open API v3 Schema based validation can be used to guard against bad requests. Invalid values for fields ( example string value for a boolean field etc) can be validated using this.
Here is a list of validations we need to support :
- The
datasetspecified in the crd should exist in k8s. - The
modelspecified in the crd should exist in k8s. - The edgenode name specified in the crd should exist in k8s.
joint inference sample
apiVersion: edgeai.io/v1alpha1
kind: JointInferenceService
metadata:
name: helmet-detection-demo
namespace: default
spec:
edgeWorker:
name: "edgeworker"
model:
name: "small-model"
nodeName: "edge0"
hardExampleAlgorithm:
name: "IBT"
workerSpec:
scriptDir: "/code"
scriptBootFile: "edge_inference.py"
frameworkType: "tensorflow"
frameworkVersion: "1.18"
parameters:
- key: "nms_threshold"
value: "0.6"
cloudWorker:
name: "work"
model:
name: "big-model"
nodeName: "solar-corona-cloud"
workerSpec:
scriptDir: "/code"
scriptBootFile: "cloud_inference.py"
frameworkType: "tensorflow"
frameworkVersion: "1.18"
parameters:
- key: "nms_threshold"
value: "0.6"
Controller Design
The joint inference controller starts three separate goroutines called upstream, downstream and joint-inferencecontroller. These are not separate controllers as such but named here for clarity.
- joint inference: watch the updates of joint-inference-task crds, and create the workers to complete the task.
- downstream: synchronize the joint-inference updates from the cloud to the edge node.
- upstream: synchronize the joint-inference updates from the edge to the cloud node.
Joint Inference Controller
The joint-inference controller watches for the updates of joint-inference tasks and the corresponding pods against the K8S API server. Updates are categorized below along with the possible actions:
| Update Type | Action |
|---|---|
| New Joint-inference-service Created | Create the aggregation worker and these local-training workers |
| Joint-inference-service Deleted | NA. These workers will be deleted by gc. |
| The corresponding pod created/running/completed/failed | Update the status of joint-inference task. |
Downstream Controller
The downstream controller watches for joint-inference updates against the K8S API server. Updates are categorized below along with the possible actions that the downstream controller can take:
| Update Type | Action |
|---|---|
| New Joint-inference-service Created | Sends the task information to LCs. |
| Joint-inference-service Deleted | The controller sends the delete event to LCs. |
Upstream Controller
The upstream controller watches for joint-inference-task updates from the edge node and applies these updates against the API server in the cloud. Updates are categorized below along with the possible actions that the upstream controller can take:
| Update Type | Action |
|---|---|
| Joint-inference-service Reported State Updated | The controller appends the reported status of the Joint-inference-service in the cloud. |
Details of api between GC(cloud) and LC(edge)
GC(downstream controller) syncs the task info to LC:
// POST <namespace>/jointinferenceservices/<name> // body same to the task crd of k8s api, omitted here.LC uploads the task status which reported by the worker to GC(upstream controller):
// POST <namespace>/jointinferenceservices/<name>/status // WorkerMessage defines the message from that the training worker. It will send to GC. type WorkerMessage struct { Phase string `json:"phase"` Status string `json:"status"` Output *WorkerOutput `json:"output"` } // type WorkerOutput struct { TaskInfo *TaskInfo `json:"taskInfo"` } // TaskInfo defines the task information type TaskInfo struct { // Current training round Uploaded int `json:"uploaded"` }
Workers Communication
Todo: complete the restful api.