> Note: If you're not seeing the `Data Sources` link in your side menu it means that your current user does not have the `Admin` role for the current organization.
| _URL_ | The URL of the Loki instance, e.g., `http://localhost:3100` |
| _Maximum lines_ | Upper limit for number of log lines returned by Loki (default is 1000). Decrease if your browser is sluggish when displaying logs in Explore. |
You can use this functionality to link to your tracing backend directly from your logs, or link to a user profile page if a userId is present in the log line. These links appear in the [log details](/features/explore/#labels-and-parsed-fields).
- **Regex:** A Regex pattern that runs on the log message and captures part of it as the value of the new field. Can only contain a single capture group.
- **URL**: A URL template used to construct a link next to the field value in log details. Use special `${__value.raw}` value in your template to interpolate the real field value into your URL template.
You can use a debug section to see what your fields extract and how the URL is interpolated. Click **Show example log message** to show the text area where you can enter a log message.
{{<docs-imageboximg="/img/docs/v65/loki_derived_fields_debug.png"class="docs-image--no-shadow"caption="Screenshot of the derived fields debugging">}}
The new field with the link shown in log details:
{{<docs-imageboximg="/img/docs/v65/loki_derived_fields_detail.png"class="docs-image--no-shadow"caption="Screenshot of the derived field in log detail">}}
Querying and displaying log data from Loki is available via [Explore]({{< relref "../explore" >}}), and with the [logs panel]({{< relref "../panels/logs/" >}}) in dashboards. Select the Loki data source, and then enter a log query to display your logs.
A log query consists of two parts: **log stream selector**, and a **search expression**. For performance reasons you need to start by choosing a log stream by selecting a log label.
The Logs Explorer (the `Log labels` button) next to the query field shows a list of labels of available log streams. An alternative way to write a query is to use the query field's autocomplete - you start by typing a left curly brace `{` and the autocomplete menu will suggest a list of labels. Press the `enter` key to execute the query.
Once the result is returned, the log panel shows a list of log rows and a bar chart where the x-axis shows the time and the y-axis shows the frequency/count.
For the label part of the query expression, wrap it in curly braces `{}` and then use the key value syntax for selecting labels. Multiple label expressions are separated by a comma:
`{app="mysql",name="mysql-backup"}`
The following label matching operators are currently supported:
*`=` exactly equal.
*`!=` not equal.
*`=~` regex-match.
*`!~` do not regex-match.
Examples:
*`{name=~"mysql.+"}`
*`{name!~"mysql.+"}`
The [same rules that apply for Prometheus Label Selectors](https://prometheus.io/docs/prometheus/latest/querying/basics/#instant-vector-selectors) apply for Loki Log Stream Selectors.
Another way to add a label selector is in the table section. Click **Filter** beside a label to add the label to the query expression. This even works for multiple queries and will add the label selector to each query.
After writing the Log Stream Selector, you can filter the results further by writing a search expression. The search expression can be just text or a regex expression.
Loki supports Live tailing which displays logs in real-time. This feature is supported in [Explore]({{< relref "../explore/#loki-specific-features" >}}).
Note that Live Tailing relies on two Websocket connections: one between the browser and the Grafana server, and another between the Grafana server and the Loki server. If you run any reverse proxies, please configure them accordingly.
> Note: This feature is only available in Grafana v6.3+
## Log Context
When using a search expression as detailed above, you now have the ability to retrieve the context surrounding your filtered results.
By clicking the `Show Context` link on the filtered rows, you'll be able to investigate the log messages that came before and after the
log message you're interested in.
> Note: This feature is only available in Grafana v6.3+
Instead of hard-coding things like server, application and sensor name in your metric queries, you can use variables in their place. Variables are shown as drop-down select boxes at the top of the dashboard. These drop-down boxes make it easy to change the data being displayed in your dashboard.
Check out the [Templating]({{< relref "../../reference/templating" >}}) documentation for an introduction to the templating feature and the different types of template variables.
You can use any non-metric Loki query as a source for annotations. Log content will be used as annotation text and your log stream labels as tags, so there is no need for additional mapping.
You can read more about how it works and all the settings you can set for data sources on the [provisioning docs page]({{< relref "../../administration/provisioning/#datasources" >}})
Here's another with basic auth and derived field. Keep in mind that `$` character needs to be escaped in yaml values as it is used to interpolate environment variables:
