> ## Documentation Index
> Fetch the complete documentation index at: https://docs.cognite.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Troubleshooting

> Solutions and instructions for troubleshooting common problems when setting up the OPC UA extractor to push data to Cognite Data Fusion (CDF).

We recommend accessing the server through the [UAExpert](https://www.unified-automation.com/products/development-tools/uaexpert.html) tool.

<Info>
  This assumes that you have first run the configuration tool as described in [the configuration settings](/cdf/integration/guides/extraction/configuration/opcua).
</Info>

## Unable to connect to the server

If the extractor isn't able to connect to the OPC UA server, try these solutions.

<AccordionGroup>
  <Accordion title="Unable to connect to discovery server">
    If you get the error message `Unable to connect to discovery server`, make sure that you have specified the correct **endpoint-url** in [the configuration file](/cdf/integration/guides/extraction/configuration/opcua) and that it's possible to connect to the server from where the extractor is running.

    Also, try connecting with [UAExpert](https://www.unified-automation.com/products/development-tools/uaexpert.html) to verify that you can connect to the server.
  </Accordion>

  <Accordion title="Identity token rejected">
    If you get the error message `Identity token rejected` when starting the extractor, verify that you have specified the correct username/password.
  </Accordion>

  <Accordion title="Certificate untrusted">
    If you get the error message `Identity token rejected` when starting the extractor, try setting `source.auto-accept` to `true` to resolve the issue.

    OPC UA uses a system of server/client certificates. This error message means that the server doesn't trust the client certificate. The server software typically has a system to accept incoming connections, but the system is application specific.

    Similar errors are also produced if the extractor rejects the server.
  </Accordion>

  <Accordion title="The extractor hangs during startup, then loses connection">
    This typically occurs if the server can't handle a high load. Try to inspect what the extractor was doing as it crashed, then reduce `source/browse-nodes-chunk`, `source/browse-chunk`, `source/attributes-chunk`, or `source/subscription-chunk` in [the configuration file](/cdf/integration/guides/extraction/configuration/opcua).

    Alternatively, increase `source/keep-alive-interval`.
  </Accordion>

  <Accordion title="There was an issue with the certificate or SHA1 signed certificates aren't trusted">
    This is an issue with the server certificate unless a custom client certificate is being used.

    By default, SHA1 server certificates are considered insecure. As a workaround, you can set `<RejectSHA1SignedCertificates>false</RejectSHA1SignedCertificates>` under `SecurityConfiguration` in `opc.ua.extractor.Config.xml`.

    You can also set `source.ignore-certificate-issues` to `true`.
  </Accordion>

  <Accordion title="Certificate doesn't meet the minimum key length requirement">
    This is an issue with the server certificate unless a custom client certificate is being used.

    Either increase the key length of the server certificate or adjust `MinimumCertificateKeySize` under `SecurityConfiguration` in `opc.ua.extractor.Config.xml`.

    You can also set `source.ignore-certificate-issues` to `true`.
  </Accordion>

  <Accordion title="Usage of certificate isn't allowed">
    This is an issue with the server certificate unless a custom client certificate is being used.

    The server certificate lacks the data-encipherment usage flag. This is required by the OPC UA standard.

    As a workaround, you can set `source.ignore-certificate-issues` to `true`.
  </Accordion>
</AccordionGroup>

## Bad or missing data

If the extractor isn't able to retrieve all data or receives data in the wrong format from the OPC UA server, try these solutions.

<AccordionGroup>
  <Accordion title="I don't get any time series">
    First, make sure that the server has variables that can be mapped to time series. In [UAExpert](https://www.unified-automation.com/products/development-tools/uaexpert.html), these show up as green labels.

    Next, try to set `extraction`/`data-types`/`allow-string-variables` to `true`. This may cause time series you would rather have as numeric to appear as string. See [Time series are string-valued but should be numerical](#time-series-are-string-valued-but-should-be-numerical).

    If the time series are still missing, the issue is most likely related to their dimensions. By default, the extractor requires that variables are either Scalar or OneDimensional. If you have arrays in your server, they must be fixed size and define the `ArrayDimensions` attribute. Try setting `extraction/data-types/unknown-as-scalar` to `true`. This will help if the variables have `ValueRank` equal to `Any` or `OneOrMoreDimensions`, in which case they will be treated as scalar.

    If variables still doesn't appear, check to make sure you haven't filtered them out in any way.
  </Accordion>

  <Accordion title="Time series are string-valued but should be numerical">
    This is generally a question of their OPC UA data type. The extractor tries to guess which mapping makes the most sense but doesn't always succeed.

    First, try setting `extraction/data-types/auto-identify-types` to `true`.

    Next, try setting `extraction/data-types/null-as-numeric` to `true`. This will treat variables with null DataType as numeric variables. Do this only if you are sure none of these should be string values. If this is the case, either filter these out or contact the server administrator. Unknown data types aren't supported by the extractor, except with this workaround.

    You can find the data type in [UAExpert](https://www.unified-automation.com/products/development-tools/uaexpert.html) on the right side after selecting a variable.
  </Accordion>

  <Accordion title="Some metadata appears as time series">
    Variables in OPC UA are mapped to time series, while properties are mapped to metadata. Sometimes the server will have variables that represent metadata. To map these over, you can use `extraction/transformations` to select the nodes you want as metadata.
  </Accordion>
</AccordionGroup>