Grafana SQLite Datasource

This is a Grafana backend plugin to allow using an SQLite database as a data source. The SQLite database needs to be accessible to the filesystem of the device where Grafana itself is running.

Plugin Installation

The most up to date (but also most generic) information can always be found here: Grafana Website - Plugin Installation

Recommended: Installing the Official and Released Plugin on an Existing Grafana With the CLI

Grafana comes with a command line tool that can be used to install plugins.

1. Run this command: grafana-cli plugins install frser-sqlite-datasource
2. Restart the Grafana server.
3. To make sure the plugin was installed, check the list of installed data sources. Click the Plugins item in the main menu. Both core data sources and installed data sources will appear.

Latest Version: Installing the newest Plugin Version on an Existing Grafana With the CLI

The grafana-cli can also install plugins from a non-standard URL. This way even plugin versions, that are not (yet) released to the official Grafana repository can be installed.

1. Run this command:

   # replace the $VERSION part in the URL below with the desired version (e.g. 2.0.2)
   grafana-cli --pluginUrl https://github.com/fr-ser/grafana-sqlite-datasource/releases/download/v$VERSION/frser-sqlite-datasource-$VERSION.zip plugins install frser-sqlite-datasource

2. See the recommended installation above (from the restart step)

Manual: Installing the Plugin Manually on an Existing Grafana

In case the grafana-cli does not work for whatever reason plugins can also be installed manually.

1. Get the zip file from Latest release on Github

2. Extract the zip file into the data/plugins subdirectory for Grafana: unzip <the_download_zip_file> -d <plugin_dir>/

   Finding the plugin directory can sometimes be a challenge as this is platform and settings dependent. A common location for this on Linux devices is /var/lib/grafana/plugins/

3. See the recommended installation above (from the restart step)

Configuring the Datasource in Grafana

The only required configuration is the path to the SQLite database (local path on the Grafana Server).

1. Add an SQLite datasource.
2. Set the path to the database (the grafana process needs to find the SQLite database under this path).
3. Save the datasource and use it.

Support for Time Formatted Columns

SQLite has no native "time" format. It relies on strings and numbers for time and dates. Since especially for time series Grafana expects an actual time type, however, the plugin provides a way to infer a real timestamp. This can be set in the query editor by providing the name of the column, which should be reformatted to a timestamp.

The plugin supports two different inputs that can be converted to a "time" depending on the type of the value in the column, that should be formatted as "time":

1. A number input: It is assumed to be a unix timestamp / unix epoch. This represents time in the number of seconds (make sure your timestamp is not in milliseconds). More information is here: https://en.wikipedia.org/wiki/Unix_time

2. A string input: The value is expected to be formatted in accordance with RFC3339, e.g. "2006-01-02T15:04:05Z07:00". Edge cases might occur and the parsing library used is the source of truth here: https://golang.org/pkg/time/#pkg-constants.

Timestamps stored as unix epoch should work out of the box, but the string formatting might require adjusting your current format. The below example shows how to convert a "date" column to a parsable timestamp:

WITH converted AS (
   -- a row looks like this (value, date): 1.45, '2020-12-12'
   SELECT value,  date || 'T00:00:00Z' AS datetime FROM raw_table
)
SELECT datetime, value FROM converted ORDER BY datetime ASC

Macros

This plugins supports macros inspired by the built-in Grafana data sources (e.g. https://grafana.com/docs/grafana/latest/datasources/postgres/#macros).

However, as each macro needs to be re-implemented from scratch, only the following macros are supported. Other macros (that you might expect from other SQL databases) are not supported by the plugin (yet).

$__unixEpochGroupSeconds(unixEpochColumnName, intervalInSeconds)

Example: $__unixEpochGroupSeconds("time", 10)

Will be replaced by an expression usable in GROUP BY clause. For example: cast(("time" / 10) as int) * 10

$__unixEpochGroupSeconds(unixEpochColumnName, intervalInSeconds, NULL)

Example: $__unixEpochGroupSeconds(timestamp, 10, NULL)

This is the same as the above example but with a fill parameter so missing points in that series will be added for Grafana and NULL will be used as value.

In case multiple time columns are provided the first one is chosen as the column to determine the gap filling. "First" in this context means first in the SELECT statement. This column needs to have no NULL values and must be sorted in ascending order.

Alerting

The plugins supports the Grafana alerting feature. Similar to the built in data sources alerting does not support variables as they are normally replaced in the frontend, which is not involved for the alerts. In order to allow time filtering this plugin supports the variables $__from and $__to. For more information about those variables see here: https://grafana.com/docs/grafana/latest/variables/variable-types/global-variables/#__from-and-__to. Formatting of those variables (e.g. ${__from:date:iso}) is not supported for alerts, however.

Common Problems / FAQ

The following section describes common issues encountered while using the plugin.

I have a "file not found" error for my database

The first choice should be to make sure, that the path is correct. It is also good practice to use absolute paths (e.g. /app/state/data.db) instead of relative paths (state/data.db).

In case the path is correct but the database is in the /var directory on a linux system there might also be a systemd issue. This is typically observed with Grafana versions starting with v8.2.0. When Grafana is run via systemd (the typical default installation on Linux systems) the /var directory is not available to Grafana (and therefore also not to the plugin).

In order to change this behavior you need to do the following:

# edit (override) the grafana systemd configuration
systemctl edit grafana-server

# add the following lines
[Service]
PrivateTmp=false

# reload the systemd config and restart the app
systemctl daemon-reload
systemctl restart grafana-server

I have a "permission denied" error for my database

Make sure, that you have access to the file and all the folders in the path of the file. Read access is enough for the plugin.

In case the permissions are correct but database is in the /home directory on a linux system there might also be a systemd issue. This is typically observed with Grafana versions starting with v8.2.0. When Grafana is run via systemd (the typical default installation on Linux systems) the /home directory is not available to Grafana (and therefore also not to the plugin).

In order to change this behavior you need to do the following:

# edit (override) the grafana systemd configuration
systemctl edit grafana-server

# add the following lines
[Service]
ProtectHome=false

# reload the systemd config and restart the app
systemctl daemon-reload
systemctl restart grafana-server

Development and Contributing

Any contribution is welcome. Some information regarding the local setup can be found in the DEVELOPMENT.md file.

Supporting the Project

This project was developed for free as an open source project. And it will stay that way.

If you like using this plugin, however, and would like to support the development go check out the Github sponsorship page. This allows sponsoring the project with monthly or one-time contributions.