> For the complete documentation index, see [llms.txt](https://v2.dataos.info/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://v2.dataos.info/concepts/resources/nilus/troubleshooting/common-errors.md).

# Common Errors

This catalog collects common Nilus failure patterns and the first recovery path to try.

## Error catalog

| Error or symptom                                                                                               | Likely cause                                                                                                               | Recovery                                                                                                                     |
| -------------------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------- |
| `Source not supported.`                                                                                        | Source URI scheme, depot mapping, or pipeline mode is not supported in the current release.                                | Check [Sources](/concepts/resources/nilus/sources.md), then use the connector page's supported URI shape.                    |
| `Sink not supported.`                                                                                          | Destination URI scheme or depot mapping is not supported.                                                                  | Check [Destinations](/concepts/resources/nilus/destinations.md), then use the destination page's supported URI shape.        |
| `Table name must be in the format <schema>.<table>`                                                            | `source_table` or `dest_table` is missing its schema/database prefix.                                                      | Use the fully qualified form required by the connector.                                                                      |
| Authentication or permission denied                                                                            | Secret projection, depot credentials, source permissions, or destination write grants are wrong.                           | Recheck [Secrets and Projections](/concepts/resources/nilus/concepts/secrets-and-projections.md) and connector requirements. |
| Empty destination table                                                                                        | Wrong source object, restrictive filters, unsupported incremental cursor, or no source changes.                            | Confirm source row count and run with a narrow known-good object.                                                            |
| Duplicate rows                                                                                                 | Append strategy used for mutable entities, missing primary key, or unstable key.                                           | Use `merge` with `primary_key` where the destination supports it.                                                            |
| CDC resume failure                                                                                             | Source change-feed retention no longer contains the last committed offset.                                                 | Increase retention and resnapshot the affected pipeline.                                                                     |
| CDC schema-history lookup failure                                                                              | Source DDL or pipeline identity changed after history was recorded.                                                        | Inspect schema-history endpoints and keep CDC identity stable.                                                               |
| Metrics are stale                                                                                              | Pushgateway retained old series or the runtime could not push metrics.                                                     | Check push age, logs, and Pushgateway connectivity.                                                                          |
| Run is slower than baseline                                                                                    | Source paging, destination load pressure, resource pressure, or data volume changed.                                       | Use [Optimizing for Time](/concepts/resources/nilus/pipeline-optimization/optimizing-for-time.md).                           |
| `Invalid Parameter - failure validating tenant resource: invalid resource dependency, not found: depot:<name>` | The pipeline references a depot that does not exist in the tenant. The Nilus runtime validates dependencies at apply time. | Create the missing depot before applying the pipeline resource. Confirm the depot name and workspace match.                  |

## Connector-specific runbooks

* [Handling MongoDB Error 286 in CDC Pipelines](/concepts/resources/nilus/troubleshooting/mongodb-cdc-error-286.md)
* [Handling MongoDB Warning BufferingChangeStreamCursor in CDC Pipelines](/concepts/resources/nilus/troubleshooting/mongodb-cdc-bufferingchangestreamcursor.md)
* [Working with partitioned tables](/concepts/resources/nilus/troubleshooting/postgresql-cdc-partitioned-tables.md)

## Related docs

* [Troubleshooting](/concepts/resources/nilus/troubleshooting.md)
* [Checking Logs](/concepts/resources/nilus/troubleshooting/checking-logs.md)
* [Schema Evolution](/concepts/resources/nilus/concepts/schema-evolution.md)
* [Pipeline Optimization](/concepts/resources/nilus/pipeline-optimization.md)


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