Grafana

Grafana is a popular observability and monitoring application used to visualize data and help with time-series data analysis. It has an extensive ecosystem of widgets and plugins. QuestDB supports connecting to Grafana via the Postgres endpoint.

Prerequisites#

Docker to run both Grafana and QuestDB

We will use the --add-host parameter for both Grafana and QuestDB.

Start Grafana#

Start Grafana using docker run:

docker run --add-host=host.docker.internal:host-gateway \
-p 3000:3000 --name=grafana \
-v grafana-storage:/var/lib/grafana \
grafana/grafana-oss

Once the Grafana server has started, you can access it via port 3000 (http://localhost:3000). The default login credentials are as follows:

user:admin
password:admin

Start QuestDB#

The Docker version for QuestDB can be run by exposing the port 8812 for the PostgreSQL connection and port 9000 for the web and REST interface:

docker run --add-host=host.docker.internal:host-gateway \
-p 9000:9000 -p 9009:9009 -p 8812:8812 -p 9003:9003 \
-e QDB_PG_READONLY_USER_ENABLED=true \
questdb/questdb:latest

Add a data source#

Open Grafana's UI (by default available at http://localhost:3000)
Go to the Configuration section and click on Data sources
Click Add data source
Choose the PostgreSQL plugin and configure it with the following settings:

host:host.docker.internal:8812
database:qdb
user:user
password:quest
TLS/SSL mode:disable

When adding a panel, use the "text edit mode" by clicking the pencil icon and adding a query

Global variables#

Use global variables to simplify queries with dynamic elements such as date range filters.

`$__timeFilter(timestamp)`#

This variable allows filtering results by sending a start-time and end-time to QuestDB. This expression evaluates to:

timestamp BETWEEN
    '2018-02-01T00:00:00Z' AND '2018-02-28T23:59:59Z'

`$__interval`#

This variable calculates a dynamic interval based on the time range applied to the dashboard. By using this function, the sampling interval changes automatically as the user zooms in and out of the panel.

Example query#

SELECT
  pickup_datetime AS time,
  avg(trip_distance) AS distance
FROM taxi_trips
WHERE $__timeFilter(pickup_datetime)
SAMPLE BY $__interval;

Known issues#

For alert queries generated by certain Grafana versions, the macro $__timeFilter(timestamp) produces timestamps with nanosecond precision, while the expected precision is millisecond precision. As a result, the alert queries are not compatible with QuestDB and lead to an Invalid date error. To resolve this, we recommend the following workaround:

SELECT
  pickup_datetime AS time,
  avg(trip_distance) AS distance
FROM taxi_trips
WHERE pickup_datetime BETWEEN cast($__unixEpochFrom()*1000000L as timestamp) and cast($__unixEpochTo()*1000000L as timestamp)

See Grafana issues for more information.