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73 lines
3.4 KiB
Markdown
73 lines
3.4 KiB
Markdown
# Interpreting common log messages
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When debugging errors and outages, looking at the logs emitted by
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JupyterHub is very helpful. This document intends to describe some common
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log messages, what they mean and what are the most common causes that generated them, as well as some possible ways to fix them.
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## Failing suspected API request to not-running server
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### Example
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Your logs might be littered with lines that look scary
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```
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[W 2022-03-10 17:25:19.774 JupyterHub base:1349] Failing suspected API request to not-running server: /hub/user/<user-name>/api/metrics/v1
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```
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### Cause
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This likely means that the user's server has stopped running but they
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still have a browser tab open. For example, you might have 3 tabs open and you shut
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the server down via one.
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Another possible reason could be that you closed your laptop and the server was culled for inactivity, then reopened the laptop!
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However, the client-side code (JupyterLab, Classic Notebook, etc) doesn't interpret the shut-down server and continues to make some API requests.
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JupyterHub's architecture means that the proxy routes all requests that
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don't go to a running user server to the hub process itself. The hub
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process then explicitly returns a failure response, so the client knows
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that the server is not running anymore. This is used by JupyterLab to
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inform the user that the server is not running anymore, and provide an option
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to restart it.
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Most commonly, you'll see this in reference to the `/api/metrics/v1`
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URL, used by [jupyter-resource-usage](https://github.com/jupyter-server/jupyter-resource-usage).
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### Actions you can take
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This log message is benign, and there is usually no action for you to take.
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## JupyterHub Singleuser Version mismatch
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### Example
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```
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jupyterhub version 1.5.0 != jupyterhub-singleuser version 1.3.0. This could cause failure to authenticate and result in redirect loops!
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```
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### Cause
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JupyterHub requires the `jupyterhub` python package installed inside the image or
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environment, the user server starts in. This message indicates that the version of
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the `jupyterhub` package installed inside the user image or environment is not
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the same as the JupyterHub server's version itself. This is not necessarily always a
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problem - some version drift is mostly acceptable, and the only two known cases of
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breakage are across the 0.7 and 2.0 version releases. In those cases, issues pop
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up immediately after upgrading your version of JupyterHub, so **always check the JupyterHub
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changelog before upgrading!**. The primary problems this _could_ cause are:
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1. Infinite redirect loops after the user server starts
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2. Missing expected environment variables in the user server once it starts
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3. Failure for the started user server to authenticate with the JupyterHub server -
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note that this is _not_ the same as _user authentication_ failing!
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However, for the most part, unless you are seeing these specific issues, the log
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message should be counted as a warning to get the `jupyterhub` package versions
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aligned, rather than as an indicator of an existing problem.
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### Actions you can take
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Upgrade the version of the `jupyterhub` package in your user environment or image
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so that it matches the version of JupyterHub running your JupyterHub server! If you
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are using the [zero-to-jupyterhub](https://z2jh.jupyter.org) helm chart, you can find the appropriate
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version of the `jupyterhub` package to install in your user image [here](https://jupyterhub.github.io/helm-chart/)
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