Culling idle notebook servers

The idle culler automatically shuts down user notebook servers when they have not been used for a certain time period, in order to reduce the total resource usage on your JupyterHub.

JupyterHub pings the user’s notebook server at certain time intervals. If no response is received from the server during this checks and the timeout expires, the server is considered to be inactive (idle) and will be culled.

Default settings

By default, JupyterHub will ping the user notebook servers every 60s to check their status. Every server found to be idle for more than 10 minutes will be culled.

services.cull.every = 60
services.cull.timeout = 600

Because the servers don’t have a maximum age set, an active server will not be shut down regardless of how long it has been up and running.

services.cull.max_age = 0

If after the culling process, there are users with no active notebook servers, by default, the users will not be culled alongside their notebooks and will continue to exist.

services.cull.users = False

Configuring the idle culler

The available configuration options are:

Idle timeout

The idle timeout is the maximum time (in seconds) a server can be inactive before it will be culled. The timeout can be configured using:

sudo tljh-config set services.cull.timeout <max-idle-sec-before-server-is-culled>
sudo tljh-config reload

Idle check interval

The idle check interval represents how frequent (in seconds) the Hub will check if there are any idle servers to cull. It can be configured using:

sudo tljh-config set services.cull.every <number-of-sec-this-check-is-done>
sudo tljh-config reload

Maximum age

The maximum age sets the time (in seconds) a server should be running. The servers that exceed the maximum age, will be culled even if they are active. A maximum age of 0, will deactivate this option. The maximum age can be configured using:

sudo tljh-config set services.cull.max_age <server-max-age>
sudo tljh-config reload

User culling

In addition to servers, it is also possible to cull the users. This is usually suited for temporary-user cases such as tmpnb. User culling can be activated using the following command:

sudo tljh-config set services.cull.users True
sudo tljh-config reload

Concurrency

Deleting a lot of users at the same time can slow down the Hub. The number of concurrent requests made to the Hub can be configured using:

sudo tljh-config set services.cull.concurrency <number-of-concurrent-hub-requests>
sudo tljh-config reload

Because TLJH it’s used for a small number of users, the cases that may require to modify the concurrency limit should be rare.

Disabling the idle culler

The idle culling service is enabled by default. To disable it, use the following command:

sudo tljh-config set services.cull.enabled False
sudo tljh-config reload