docs: Describe how to use Grafana to query logs

docs/docs/admin/monitoring/logging/data_source_picker.png.license

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+SPDX-FileCopyrightText: Copyright DB InfraGO AG and contributors
+SPDX-License-Identifier: Apache-2.0

docs/docs/admin/monitoring/logging/explore.png.license

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+SPDX-FileCopyrightText: Copyright DB InfraGO AG and contributors
+SPDX-License-Identifier: Apache-2.0

docs/docs/admin/monitoring/logging/explorer.md

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+<!--
+ ~ SPDX-FileCopyrightText: Copyright DB InfraGO AG and contributors
+ ~ SPDX-License-Identifier: Apache-2.0
+ -->
+
+# Grafana Log Explorer
+
+!!! note
+
+    The Log Explorer is only available if Grafana Loki was enabled during deployment.
+
+The Grafana Explorer can be used to view the logs of different components, such
+as the backend or user sessions. The logs are stored persistently, so
+administrators can also view the logs of already terminated sessions, for
+example to investigate an unexpected session termination.
+
+The Grafana Explorer is available to administrators and can be accessed from
+the Grafana link in the main menu. Select "Explore" to access the log explorer:
+
+![Explore in the main Grafana menu](./explore.png){:style="width:300px"}
+
+## Select the Correct Source
+
+Before you can view logs, you must make sure that the correct source is
+selected for the Capella Collaboration Manager. For this please select **Loki
+(Capella Collaboration Manager)** in the data source picker.
+
+![Select Capella Collaboration Manager in Data Source Picker](./data_source_picker.png){:style="width:500px"}
+
+## Time Range Selector
+
+Even though Loki is quite efficient, it is still not feasible to always query
+all the data, so you need to select the time range for which you want to see
+the logs, or use the default "Last 1 hour" time range. To change the time
+range, open the drop-down menu in the top right corner and select the time
+range you want to see.
+
+![Time Range Picker](./time_range.png){:style="width:450px"}
+
+## Label Filters
+
+The application logs are stored in Loki, which uses labels to store and
+retrieve logs efficiently. This means that each log in Loki has a set of labels
+assigned to it, where a label is essentially a key-value pair.
+
+You have to select at least one label and a corresponding value to query logs.
+To do this, open the **Select Label** drop-down, select a label, and then click
+**Select Value**, which will load the values that exist for the label and allow
+you to select a value.
+
+![Select Log Label and Value](./label_filters.png){:style="width:300px"}
+
+It is also possible to add multiple label filters by clicking the plus icon.
+When you do this, you must first select a label and value for the first filter,
+and when you select the second label, you will only see labels that can be
+combined with the first filter. For example, if the first filter limits the
+logs to backend logs, you won't be able to select anything else, while if the
+first filter limits the logs to session logs, you can further restrict the
+tool, version, etc.
+
+You can query logs of different components by selecting the following labels:
+
+-   **Management portal logs**: If you want to query the logs of the management
+    portal, make use of the `deployment` label to select a component of the
+    management portal.
+-   **Session logs**: If you want to query the logs of a specific session, you
+    can use the `username` label to select the user, and the `session_type`
+    label to select the session type. You can also use the `tool` and `version`
+    labels to further specify the session.
+-   **Pipeline logs**: If you want to query the logs of a pipeline, you can use
+    the `pipeline_run_id` label to select the pipeline run. The pipeline run
+    identifiers are listed in the pipeline run overview of a pipeline.
+
+Here is an example filter how to select all sessions for version 7.0.0.
+
+![Example Label Filter](./label_filter_example.png){:style="width:800px"}
+
+## Operations
+
+Now as you have some logs selected by the label filters, there are some useful
+operations that you can run. Due to the large number of supported operations,
+this guide will only cover examples that are often used in our context.
+
+### Line Contains
+
+The line contains operations that essentially search the log messages for the
+text you want to find.
+
+![Log Operations](./operations.png){:style="width:400px"}
+
+### Backend Logfmt
+
+For our backend logs, we follow the [logfmt](https://brandur.org/logfmt), which
+provides more structure to the log lines and is especially useful when used
+with Loki/Grafana. The reason for this is that you can use the `Logfmt`
+operation to convert the key-value pairs in our logs to labels. These labels
+can then be used to filter the logs more fine-grained and efficiently.
+
+Here is an example operation sequence where you can query all logs that have
+the log level **INFO** and the HTTP method **POST**.
+
+![Operations Example](./operations_example.png){:style="width:500px"}
+
+Theoretically, you could achieve the same result by changing two line contains
+operations, but it's inefficient and you have to use the exact format as in the
+log message.
+
+![Operations Example without Logfmt](./operations_example_bad.png){:style="width:400px"}
+
+## Run Query
+
+Once you have selected the appropriate label filters, added your operations,
+and the time range for which you want to see the logs, you can execute the
+query by clicking the query by clicking the **Run Query** button in the upper
+right corner. The logs will then be queried, which may take a moment depending
+on the time range you have selected and then displayed in the logs view (if you
+do not see it, just scroll down a bit).
+
+![Run Query](./run_query.png){:style="width:400px"}

docs/docs/admin/monitoring/logging/label_filter_example.png.license

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+SPDX-FileCopyrightText: Copyright DB InfraGO AG and contributors
+SPDX-License-Identifier: Apache-2.0

docs/docs/admin/monitoring/logging/label_filters.png.license

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+SPDX-FileCopyrightText: Copyright DB InfraGO AG and contributors
+SPDX-License-Identifier: Apache-2.0

docs/docs/admin/monitoring/logging/operations.png.license

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+SPDX-FileCopyrightText: Copyright DB InfraGO AG and contributors
+SPDX-License-Identifier: Apache-2.0

docs/docs/admin/monitoring/logging/operations_example.png.license

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+SPDX-FileCopyrightText: Copyright DB InfraGO AG and contributors
+SPDX-License-Identifier: Apache-2.0

docs/docs/admin/monitoring/logging/operations_example_bad.png.license

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+SPDX-FileCopyrightText: Copyright DB InfraGO AG and contributors
+SPDX-License-Identifier: Apache-2.0

docs/docs/admin/monitoring/logging/run_query.png.license

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+SPDX-FileCopyrightText: Copyright DB InfraGO AG and contributors
+SPDX-License-Identifier: Apache-2.0

docs/docs/admin/monitoring/logging/time_range.png.license

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+SPDX-FileCopyrightText: Copyright DB InfraGO AG and contributors
+SPDX-License-Identifier: Apache-2.0

docs/mkdocs.yml

@@ -83,6 +83,7 @@ nav:
       - Monitoring:
           - Alerting: admin/monitoring/alerting.md
           - Dashboards: admin/monitoring/dashboards.md
+          - Grafana Log Explorer: admin/monitoring/logging/explorer.md
           - Pipelines & Model Modifiers: admin/monitoring/frontend.md
       - Integrations:
           - Git: admin/settings/model-sources/git.md