Advanced Topics

This page contains a grab bag of various useful topics that don’t have an easy home elsewhere:

  • Ingress
  • Arbitrary extra code and configuration in jupyterhub_config.py

Most people setting up JupyterHubs on popular public clouds should not have to use any of this information, but these topics are essential for more complex installations.

Ingress

If you are using a Kubernetes Cluster that does not provide public IPs for services directly, you need to use an ingress to get traffic into your JupyterHub. This varies wildly based on how your cluster was set up, which is why this is in the ‘Advanced’ section.

You can enable the required ingress object with the following in your config.yaml

ingress:
  enabled: true
  hosts:
    - <hostname>

You can specify multiple hosts that should be routed to the hub by listing them under ingress.hosts.

Note that you need to install and configure an Ingress Controller for the ingress object to work.

We recommend the community-maintained nginx-ingress controller, kubernetes/ingress-nginx. Note that Nginx maintains two additional ingress controllers. For most use cases, we recommend the community maintained kubernetes/ingress-nginx since that is the ingress controller that the development team has the most experience using.

Ingress and Automatic HTTPS with kube-lego & Let’s Encrypt

When using an ingress object, the default automatic HTTPS support does not work. To have automatic fetch and renewal of HTTPS certificates, you must set it up yourself.

Here’s a method that uses kube-lego to automatically fetch and renew HTTPS certificates from Let’s Encrypt. This approach with kube-lego and Let’s Encrypt currently only works with two ingress controllers: the community-maintained kubernetes/ingress-nginx and google cloud’s ingress controller.

  1. Make sure that DNS is properly set up (configuration depends on the ingress controller you are using and how your cluster was set up). Accessing <hostname> from a browser should route traffic to the hub.

  2. Install & configure kube-lego using the kube-lego helm-chart. Remember to change config.LEGO_EMAIL and config.LEGO_URL at the least.

  3. Add an annotation + TLS config to the ingress so kube-lego knows to get certificates for it:

    ingress:
  annotations:
    kubernetes.io/tls-acme: "true"
  tls:
   - hosts:
      - <hostname>
     secretName: kubelego-tls-jupyterhub

This should provision a certificate, and keep renewing it whenever it gets close to expiry!

Arbitrary extra code and configuration in jupyterhub_config.py

Sometimes the various options exposed via the helm-chart’s values.yaml is not enough, and you need to insert arbitrary extra code / config into jupyterhub_config.py. This is a valuable escape hatch for both prototyping new features that are not yet present in the helm-chart, and also for installation-specific customization that is not suited for upstreaming.

There are four properties you can set in your config.yaml to do this.

hub.extraConfig

The value specified for hub.extraConfig is evaluated as python code at the end of jupyterhub_config.py. You can do anything here since it is arbitrary Python Code. Some examples of things you can do:

  1. Override various methods in the Spawner / Authenticator by subclassing them. For example, you can use this to pass authentication credentials for the user (such as GitHub OAuth tokens) to the environment. See the JupyterHub docs for an example.
  2. Specify traitlets that take callables as values, allowing dynamic per-user configuration.
  3. Set traitlets for JupyterHub / Spawner / Authenticator that are not currently supported in the helm chart

Unfortunately, you have to write your python in your YAML file. There’s no way to include a file in config.yaml.

You can specify hub.extraConfig as a raw string (remember to use the | for multi-line YAML strings):

hub:
  extraConfig: |
    import time
    c.Spawner.environment += {
       "CURRENT_TIME": str(time.time())
    }

You can also specify hub.extraConfig as a dictionary, if you want to logically split your customizations. The code will be evaluated in alphabetical sorted order of the key.

hub:
  extraConfig:
    00-first-config: |
      # some code
    10-second-config: |
      # some other code

custom configuration

The contents of values.yaml is passed through to the Hub image. You can access these values via the z2jh.get_config function, for further customization of the hub pod. Version 0.8 of the chart adds a top-level custom field for passing through additional configuration that you may use. It can be arbitrary YAML. You can use this to separate your code (which goes in hub.extraConfig) from your config (which should go in custom).

For example, if you use the following snippet in your config.yaml file:

custom:
  myString: Hello!
  myList:
    - Item1
    - Item2
  myDict:
    key: value
  myLongString: |
    Line1
    Line2

In your hub.extraConfig,

  1. z2jh.get_config('custom.myString') will return a string "Hello!"
  2. z2jh.get_config('custom.myList') will return a list ["Item1", "Item2"]
  3. z2jh.get_config('custom.myDict') will return a dict {"key": "value"}
  4. z2jh.get_config('custom.myLongString') will return a string "Line1\nLine2"
  5. z2jh.get_config('custom.nonExistent') will return None (since you didn’t specify any value for nonExistent)
  6. z2jh.get_config('custom.myDefault', True) will return True, since that is specified as the second parameter (default)

You need to have a import z2jh at the top of your extraConfig for z2jh.get_config() to work.

Changed in version 0.8: hub.extraConfigMap used to be required for specifying additional values to pass, which was more restrictive. hub.extraConfigMap is deprecated in favor of the new top-level custom field, which allows fully arbitrary yaml.

hub.extraEnv

This property takes a dictionary that is set as environment variables in the hub container. You can use this to either pass in additional config to code in your hub.extraConfig or set some hub parameters that are not settable by other means.

hub.extraContainers

A list of extra containers that are bundled alongside the hub container in the same pod. This is a common pattern in kubernetes that as a long list of cool use cases. Some example use cases are:

  1. Database Proxies, which are sometimes required for the hub to talk to its configured database (in Google Cloud) for example
  2. Servers / other daemons that are used by code in your hub.customConfig

The items in this list must be valid kubernetes container specifications.

Specifying suitable hub storage

By default, the hub’s sqlite-pvc setting will dynamically create a disk to store the sqlite database. It is possible to configure other storage classes under hub.db.pvc, but make sure to choose one that the hub can write quickly and safely to. Slow or higher latency storage classes can cause hub operations to lag which may ultimately lead to HTTP errors in user environments.

FAQ Appendix: Projecting deployment costs