[[ml-troubleshooting]]
== {xpackml} Troubleshooting

Use the information in this section to troubleshoot common problems and find
answers for frequently asked questions.

To get help, see <<xpack-help>>.

[float]
[[ml-rollingupgrade]]
=== Machine learning features unavailable after rolling upgrade

This problem occurs after you upgrade all of the nodes in your cluster to
{version} by using rolling upgrades. When you try to use {xpackml} features for
the first time, all attempts fail, though `GET _xpack` and `GET _xpack/usage`
indicate that {xpack} is enabled.

*Symptoms:*

* Errors when you click *Machine Learning* in {kib}.
For example: `Jobs list could not be created` and `An internal server error occurred`.
* Null pointer and remote transport exceptions when you run {ml} APIs such as
`GET _xpack/ml/anomaly_detectors` and `GET _xpack/ml/datafeeds`.
* Errors in the log files on the master nodes.
For example: `unable to install ml metadata upon startup`

*Resolution:*

After you upgrade all master-eligible nodes to {es} {version} and {xpack}
{version}, restart the current master node, which triggers the {xpackml}
features to re-initialize.

For more information, see {ref}/rolling-upgrades.html[Rolling upgrades].