Invoke Applications

Applications can be invoked in three following ways.

Test UI call

You can perform a test request to the application from UI interface. Open a desired application and press Test button. Internally it will generate dummy input data from model’s contract and send an HTTP-request to API endpoint.


You can reach your application with an HTTP-request. Send a POST request to http://<host>/gateway/applications/{applicationName}/{applicationSignature}.

Note, when you create a pipeline application, ML Lambda internally infers a contract. It performs validation that every stage is compatible with it’s siblings, and creates a contract with the same signature name, as the application name. singular applications by default use their explicitly defined signatures.

gRPC API call

You can define a gRPC client on your side, establish insecure connection with http://<host> and make a call to Predict method. We provide an example Python client.

import grpc 
import hydro_serving_grpc as hs  # pip install hydro-serving-grpc

# connect to your ML Lamba instance
channel = grpc.insecure_channel("<host>")
stub = hs.PredictionServiceStub(channel)

# 1. define a model, that you'll use
model_spec = hs.ModelSpec(name="model", signature_name="infer")

# 2. define tensor_shape for Tensor instance
tensor_shape = hs.TensorShapeProto(
    dim=[hs.TensorShapeProto.Dim(size=-1), hs.TensorShapeProto.Dim(size=2)])

# 3. define tensor with needed data
tensor = hs.TensorProto(dtype=hs.DT_DOUBLE, tensor_shape=tensor_shape, double_val=[1,1,1,1])

# 4. create PredictRequest instance
request = hs.PredictRequest(model_spec=model_spec, inputs={"x": tensor})

# call Predict method
result = stub.Predict(request)

What’s next?