Metaflow provides a client API that is used to inspect results of past runs. It is particularly well suited to being used in notebooks.
This document provides an overview of the client API.
Note that all operations in the Client API are filtered by the current namespace, as explained in Organizing Results. If you do not get the results you expect, make sure you are in the correct namespace. The Client API consults the metadata service to gather results, so make sure that the client is properly configured to use the correct metadata provider.
These objects can be instantiated simply with
# Flow objectflow <- flow_client$new("HelloWorldFlow")# Run objectrun <- run_client$new(flow, run_id)# run_id is 12run <- run_client$new("HelloWorldFlow/12")# Step objectstep <- step_client$new(run, step_name)# step_name is startstep <- step_client$new("HelloWorldFlow/12/start")# Task objecttask <- task_client$new(step, task_id)# task_id is 12345678task <- task_client$new("HelloWorldFlow/12/start/12345678")# Data Artifacttask$artifact("my_var")
Every object listed above follows a consistent interface. All the operations below are available in all objects, not just the ones demonstrated.
# list all past runsmetaflow::list_flows()# list all past runs of the flow object# shows a list of strings of run_idprint(flow$runs)# list all step names of the run object# shows a list of strings of step namesprint(run$steps)# list all task id of the step object# shows a list of strings of task_idprint(step$tasks)
You can access a specific child simply by
helloflow <- flow_client$new("HelloFlow")run <- helloflow$run("2")
One of the most typical use cases of the client API is to access data artifacts produced by runs. Each data artifact is represented by a
DataArtifact object whose parent is a
DataArtifact is a container object for the actual value. Besides the value,
DataArtifact includes metadata about the artifact, such as its time of creation.
Often you are only interested in the value of an artifact. For this typical use case we provide a convenience property
$data in the
Task object. The
$data property returns a container which has all artifacts produced by the task as attributes.
For instance, this the shortest way to access a value produced by a step in a run:
task <- task_client$new("DebugFlow/2/compute/123")print(task$artifact("my_var"))
Here, we print the value of
self$my_varx in the step
compute of the run
123 of the flow
You can check the full object documentation by:
Every object has the following common properties available:
tags: tags assigned to the object
created_at: creation timestamp
finished_at: finish timestamp
parent: parent object
pathspec: object fully qualified name
You can find more details in the object documentation.
The Client API relies on a metadata service to gather results appropriately. Metaflow supports a local mode (
.metaflow directory on your filesystem) and a remote mode.
# Fetch currently configured metadata providermetaflow::get_metadata()# Configure Client to use local metadata provider globallymetaflow::set_metadata('/Users/bob/metaflow')# Configure Client to use remote metadata provider globallymetaflow::set_metadata('https://localhost:5000/mymetaflowservice')
Note that changing the metadata provider is a global operation and all subsequent client operations will use the metadata provider specified.