Servers

By default Seldon installs two server farms using MLServer and Triton with 1 replica each. Models are scheduled onto servers based on the server’s resources and whether the capabilities of the server matches the requirements specified in the Model request. For example:

apiVersion: mlops.seldon.io/v1alpha1
kind: Model
metadata:
  name: iris
spec:
  storageUri: "gs://seldon-models/scv2/samples/mlserver_1.6.0/iris-sklearn"
  requirements:
  - sklearn
  memory: 100Ki

This model specifies the requirement sklearn

There is a default capabilities for each server as follows:

• MLServer

          value: "mlserver,alibi-detect,alibi-explain,huggingface,lightgbm,mlflow,python,sklearn,spark-mlib,xgboost"
  

• Triton

          value: "triton,dali,fil,onnx,openvino,python,pytorch,tensorflow,tensorrt"
  

Custom Capabilities

Servers can be defined with a capabilities field to indicate custom configurations (e.g. Python dependencies). For instance:

apiVersion: mlops.seldon.io/v1alpha1
kind: Server
metadata:
  name: mlserver-134
spec:
  serverConfig: mlserver
  capabilities:
  - mlserver-1.3.4
  podSpec:
    containers:
    - image: seldonio/mlserver:1.3.4
      name: mlserver

These capabilities override the ones from the serverConfig: mlserver. A model that takes advantage of this is shown below:

apiVersion: mlops.seldon.io/v1alpha1
kind: Model
metadata:
  name: iris
spec:
  storageUri: "gs://seldon-models/mlserver/iris"
  requirements:
  - mlserver-1.3.4

This above model will be matched with the previous custom server mlserver-134.

Servers can also be set up with the extraCapabilities that add to existing capabilities from the referenced ServerConfig. For instance:

apiVersion: mlops.seldon.io/v1alpha1
kind: Server
metadata:
  name: mlserver-extra
spec:
  serverConfig: mlserver
  extraCapabilities:
  - extra

This server, mlserver-extra, inherits a default set of capabilities via serverConfig: mlserver. These defaults are discussed above. The extraCapabilities are appended to these to create a single list of capabilities for this server.

Models can then specify requirements to select a server that satisfies those requirements as follows.

apiVersion: mlops.seldon.io/v1alpha1
kind: Model
metadata:
  name: extra-model-requirements
spec:
  storageUri: "gs://seldon-models/mlserver/iris"
  requirements:
  - extra

The capabilities field takes precedence over the extraCapabilities field.

For some examples see here.

Autoscaling of Servers

Within docker we don’t support this but for Kubernetes see here