Sandbox Frequently Asked Questions

Having issues with the Sandbox? Check out this FAQ before contacting our support team.

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Kernel crash or restart

The Digital Earth Africa Sandbox has a finite amount of processing power allocated to each user. This means if you attempt to load or calculate a lot of data, the kernel may crash. You will have to rerun your notebook to continue working. However, if the notebook is still demanding too many resources, it will crash again. You can prevent kernel crashes by:

  • Decreasing the area selected for data processing

  • Shortening the time extent

  • Shutting down kernels of notebooks you have finished using: open the notebook and select Kernel -> Shut Down Kernel

These actions reduce the memory load of your computation on the Sandbox.

File Save Error: 502 Bad Gateway

Your disk may be full. Users are allocated a finite space for files. Delete large files to free up more disk space. You can back up files to your local drive by right-clicking the file and selecting “Download”. Note that large files may take a long time to download.

Pod not responding

If you demand too much compute from the Sandbox, it can cause the pod to stop responding. The kernel will not be able to be restarted and all further compute requests will not run. You may experience a 502 Gateway error. Please contact the support team at helpdesk@digitalearthafrica.org with details.

Pod failed to spawn

This can intermittently happen when logging in to the Sandbox and starting up a server. Refresh your browser and follow the prompts to relaunch the server. If the problem persists after more than 6 retries, please send an email to helpdesk@digitalearthafrica.org.

Dask spill to disk errors

Dask-enabled notebooks may throw errors such as “No space left on device”. This is caused by Dask spilling data to disk when memory limits are reached.

We suggest trying the following options:

  1. Edit the Dask config file to prevent spilling to disk. Open a Terminal from the Sandbox Launcher. Using vi or another text editor of your choice, open dask/distributed.yaml by typing the following code into the Terminal line and pressing the Enter key.

vi ~/.config/dask/distributed.yaml

Use arrow keys to navigate the file and press i to start editing. As instructed here, change the following settings to match:

distributed:
    worker:
       memory:
          target: false  # don't spill to disk
          spill: false  # don't spill to disk
          pause: 0.80  # pause execution at 80% memory use
          terminate: 0.95  # restart the worker at 95% use

Once you have edited the settings, press the following keys: Esc, :, w, q, Enter. This writes to the file then closes it.

  1. Enforce temporary directory filepath to a location outside the user’s home directory. Set the location inside a .ipynb notebook code cell by running the following code:

    import dask
    dask.config.set({'temporary_directory': '/tmpfs'})