Deploying on VMs¶

You can deploy your Serve application to production on a Ray cluster using the Ray Serve CLI. serve deploy takes in a config file path and it deploys that file to a Ray cluster over HTTP. This could either be a local, single-node cluster as in this example or a remote, multi-node cluster started with the Ray Cluster Launcher.

This section should help you:

  • understand how to deploy a Ray Serve config file using the CLI.

  • understand how to update your application using the CLI.

  • understand how to deploy to a remote cluster started with the Ray Cluster Launcher.

Let’s start by deploying the config for the FruitStand example:

$ ls
fruit.py
fruit_config.yaml

$ ray start --head
...

$ serve deploy fruit_config.yaml
2022-06-20 17:26:31,106	SUCC scripts.py:139 --
Sent deploy request successfully!
 * Use `serve status` to check deployments' statuses.
 * Use `serve config` to see the running app's config.

ray start --head starts a long-lived Ray cluster locally. serve deploy fruit_config.yaml deploys the fruit_config.yaml file to this local cluster. To stop your Ray cluster, you can run the CLI command ray stop.

The message Sent deploy request successfully! means:

  • The Ray cluster has received your config file successfully.

  • It will start a new Serve application if one hasn’t already started.

  • The Serve application will deploy the deployments from your deployment graph, updated with the configurations from your config file.

It does not mean that your Serve application, including your deployments, has already started running successfully. This happens asynchronously as the Ray cluster attempts to update itself to match the settings from your config file. Check out the next section to learn more about how to get the current status.

Adding a runtime environment¶

The import path (e.g., fruit:deployment_graph) must be importable by Serve at runtime. When running locally, this might be in your current working directory. However, when running on a cluster you also need to make sure the path is importable. You can achieve this either by building the code into the cluster’s container image (see Cluster Configuration for more details) or by using a runtime_env with a remote URI that hosts the code in remote storage.

As an example, we have pushed a copy of the FruitStand deployment graph to GitHub. You can use this config file to deploy the FruitStand deployment graph to your own Ray cluster even if you don’t have the code locally:

import_path: fruit:deployment_graph

runtime_env:
    working_dir: "https://github.com/ray-project/serve_config_examples/archive/HEAD.zip"

Note

As a side note, you could also package your deployment graph into a standalone Python package that can be imported using a PYTHONPATH to provide location independence on your local machine. However, it’s still best practice to use a runtime_env, to ensure consistency across all machines in your cluster.

Using a remote cluster¶

By default, serve deploy deploys to a cluster running locally. However, you should also use serve deploy whenever you want to deploy your Serve application to a remote cluster. serve deploy takes in an optional --address/-a argument where you can specify your remote Ray cluster’s dashboard agent address. This address should be of the form:

[RAY_CLUSTER_URI]:[DASHBOARD_AGENT_PORT]

As an example, the address for the local cluster started by ray start --head is http://127.0.0.1:52365. We can explicitly deploy to this address using the command

$ serve deploy config_file.yaml -a http://127.0.0.1:52365

The Ray dashboard agent’s default port is 52365. You can set it to a different value using the --dashboard-agent-listen-port argument when running ray start.”

Note

If the port 52365 (or whichever port you specify with --dashboard-agent-listen-port) is unavailable when Ray starts, the dashboard agent’s HTTP server will fail. However, the dashboard agent and Ray will continue to run. You can check if an agent’s HTTP server is running by sending a curl request: curl http://{node_ip}:{dashboard_agent_port}/api/serve/deployments/. If the request succeeds, the server is running on that node. If the request fails, the server is not running on that node. To launch the server on that node, terminate the process occupying the dashboard agent’s port, and restart Ray on that node.

Tip

By default, all the Serve CLI commands assume that you’re working with a local cluster. All Serve CLI commands, except serve start and serve run use the Ray agent address associated with a local cluster started by ray start --head. However, if the RAY_AGENT_ADDRESS environment variable is set, these Serve CLI commands will default to that value instead.

Similarly, serve start and serve run, use the Ray head node address associated with a local cluster by default. If the RAY_ADDRESS environment variable is set, they will use that value instead.

You can check RAY_AGENT_ADDRESS’s value by running:

$ echo $RAY_AGENT_ADDRESS

You can set this variable by running the CLI command:

$ export RAY_AGENT_ADDRESS=[YOUR VALUE]

You can unset this variable by running the CLI command:

$ unset RAY_AGENT_ADDRESS

Check for this variable in your environment to make sure you’re using your desired Ray agent address.

Inspecting the application with serve config and serve status¶

The Serve CLI also offers two commands to help you inspect your Serve application in production: serve config and serve status. If you’re working with a remote cluster, serve config and serve status also offer an --address/-a argument to access your cluster. Check out the previous section for more info on this argument.

serve config gets the latest config file the Ray cluster received. This config file represents the Serve application’s goal state. The Ray cluster will constantly attempt to reach and maintain this state by deploying deployments, recovering failed replicas, and more.

Using the fruit_config.yaml example from an earlier section:

$ ray start --head
$ serve deploy fruit_config.yaml
...

$ serve config
import_path: fruit:deployment_graph

runtime_env: {}

deployments:

- name: MangoStand
  num_replicas: 2
  route_prefix: null
...

serve status gets your Serve application’s current status. It’s divided into two parts: the app_status and the deployment_statuses.

The app_status contains three fields:

  • status: a Serve application has four possible statuses:

    • "NOT_STARTED": no application has been deployed on this cluster.

    • "DEPLOYING": the application is currently carrying out a serve deploy request. It is deploying new deployments or updating existing ones.

    • "RUNNING": the application is at steady-state. It has finished executing any previous serve deploy requests, and it is attempting to maintain the goal state set by the latest serve deploy request.

    • "DEPLOY_FAILED": the latest serve deploy request has failed.

  • message: provides context on the current status.

  • deployment_timestamp: a unix timestamp of when Serve received the last serve deploy request. This is calculated using the ServeController’s local clock.

The deployment_statuses contains a list of dictionaries representing each deployment’s status. Each dictionary has three fields:

  • name: the deployment’s name.

  • status: a Serve deployment has three possible statuses:

    • "UPDATING": the deployment is updating to meet the goal state set by a previous deploy request.

    • "HEALTHY": the deployment is at the latest requests goal state.

    • "UNHEALTHY": the deployment has either failed to update, or it has updated and has become unhealthy afterwards. This may be due to an error in the deployment’s constructor, a crashed replica, or a general system or machine error.

  • message: provides context on the current status.

You can use the serve status command to inspect your deployments after they are deployed and throughout their lifetime.

Using the fruit_config.yaml example from an earlier section:

$ ray start --head
$ serve deploy fruit_config.yaml
...

$ serve status
app_status:
  status: RUNNING
  message: ''
  deployment_timestamp: 1655771534.835145
deployment_statuses:
- name: MangoStand
  status: HEALTHY
  message: ''
- name: OrangeStand
  status: HEALTHY
  message: ''
- name: PearStand
  status: HEALTHY
  message: ''
- name: FruitMarket
  status: HEALTHY
  message: ''
- name: DAGDriver
  status: HEALTHY
  message: ''

serve status can also be used with KubeRay (Overview), a Kubernetes operator for Ray Serve, to help deploy your Serve applications with Kubernetes. There’s also work in progress to provide closer integrations between some of the features from this document, like serve status, with Kubernetes to provide a clearer Serve deployment story.

Updating the Serve application¶

You can update your Serve applications once they’re in production by updating the settings in your config file and redeploying it using the serve deploy command. In the redeployed config file, you can add new deployment settings or remove old deployment settings. This is because serve deploy is idempotent, meaning your Serve application’s config always matches (or honors) the latest config you deployed successfully – regardless of what config files you deployed before that.

Lightweight Config Updates¶

Lightweight config updates modify running deployment replicas without tearing them down and restarting them, so there’s less downtime as the deployments update. For each deployment, modifying num_replicas, autoscaling_config, and/or user_config is considered a lightweight config update, and won’t tear down the replicas for that deployment.

Note

Lightweight config updates are only possible for deployments that are included as entries under deployments in the config file. If a deployment is not included in the config file, replicas of that deployment will be torn down and brought up again each time you redeploy with serve deploy.

Updating User Config¶

Let’s use the FruitStand deployment graph from an earlier section as an example. All the individual fruit deployments contain a reconfigure() method. This method allows us to issue lightweight updates to our deployments by updating the user_config.

First let’s deploy the graph. Make sure to stop any previous Ray cluster using the CLI command ray stop for this example:

$ ray start --head
$ serve deploy fruit_config.yaml
...

$ python

>>> import requests
>>> requests.post("http://localhost:8000/", json=["MANGO", 2]).json()

6

Now, let’s update the price of mangos in our deployment. We can change the price attribute in the MangoStand deployment to 5 in our config file:

import_path: fruit:deployment_graph

runtime_env: {}

deployments:

- name: MangoStand
  num_replicas: 2
  route_prefix: null
  max_concurrent_queries: 100
  user_config:
    # price: 3 (Outdated price)
    price: 5
  autoscaling_config: null
  graceful_shutdown_wait_loop_s: 2.0
  graceful_shutdown_timeout_s: 20.0
  health_check_period_s: 10.0
  health_check_timeout_s: 30.0
  ray_actor_options: null

...

Without stopping the Ray cluster, we can redeploy our graph using serve deploy:

$ serve deploy fruit_config.yaml
...

We can inspect our deployments with serve status. Once the app_status’s status returns to "RUNNING", we can try our requests one more time:

$ serve status
app_status:
  status: RUNNING
  message: ''
  deployment_timestamp: 1655776483.457707
deployment_statuses:
- name: MangoStand
  status: HEALTHY
  message: ''
- name: OrangeStand
  status: HEALTHY
  message: ''
- name: PearStand
  status: HEALTHY
  message: ''
- name: FruitMarket
  status: HEALTHY
  message: ''
- name: DAGDriver
  status: HEALTHY
  message: ''

$ python

>>> import requests
>>> requests.post("http://localhost:8000/", json=["MANGO", 2]).json()

10

The price has updated! The same request now returns 10 instead of 6, reflecting the new price.

Code Updates¶

Similarly, you can update any other setting in any deployment in the config file. If a deployment setting other than num_replicas, autoscaling_config, or user_config is changed, it is considered a code update, and the deployment replicas will be restarted. Note that the following modifications are all considered “changes”, and will trigger tear down of replicas:

  • changing an existing setting

  • adding an override setting that was previously not present in the config file

  • removing a setting from the config file

Note also that changing import_path or runtime_env is considered a code update for all deployments, and will tear down all running deployments and restart them.

Warning

Although you can update your Serve application by deploying an entirely new deployment graph using a different import_path and a different runtime_env, this is NOT recommended in production.

The best practice for large-scale code updates is to start a new Ray cluster, deploy the updated code to it using serve deploy, and then switch traffic from your old cluster to the new one.

Best practices¶

This section summarizes the best practices when deploying to production using the Serve CLI:

  • Use serve run to manually test and improve your deployment graph locally.

  • Use serve build to create a Serve config file for your deployment graph.

    • Put your deployment graph’s code in a remote repository and manually configure the working_dir or py_modules fields in your Serve config file’s runtime_env to point to that repository.

  • Use serve deploy to deploy your graph and its deployments to your Ray cluster. After the deployment is finished, you can start serving traffic from your cluster.

  • Use serve status to track your Serve application’s health and deployment progress.

  • Use serve config to check the latest config that your Serve application received. This is its goal state.

  • Make lightweight configuration updates (e.g. num_replicas or user_config changes) by modifying your Serve config file and redeploying it with serve deploy.

  • Make heavyweight code updates (e.g. runtime_env changes) by starting a new Ray cluster, updating your Serve config file, and deploying the file with serve deploy to the new cluster. Once the new deployment is finished, switch your traffic to the new cluster.