Syntax

Create Trigger

The syntax for creating a Trigger:

CREATE TRIGGER [IF NOT EXISTS] <trigger_name>
        ON (<query_expression>) EVERY <interval_expression>
        [LABELS (<label_name>=<label_val>, ...)]
        [ANNOTATIONS (<annotation_name>=<annotation_val>, ...)]
        NOTIFY (
                WEBHOOK <notify_name1> URL '<url1>' [WITH (<parameter1>=<value1>, ...)],
                WEBHOOK <notify_name2> URL '<url2>' [WITH (<parameter2>=<value2>, ...)]
        );

Trigger name

• Trigger name: the unique identifier of the Trigger at the catalog level.
• IF NOT EXISTS: prevent errors that would occur if the Trigger being created.

On clause

Query expression

The SQL query which be executed periodically. The notification will be fired if query result is not empty. If query result has multiple rows, a notification will be fired for each row.

In addition, the Trigger will extract the labels and annotations from the query result, and attach them to the notification message along with the key-value pairs specified in the LABELS and ANNOTATIONS clauses.

The extraction rules are as follows:

• Extract columns whose name or alias starts with label_ to LABELS. The key of labels is the column name or alias without the label_ prefix.
• Extract the other columns to ANNOTATIONS. The key of annotations is the column name.

For example, the query expression is as follows:

SELECT collect as label_collector, host as label_host, val
    FROM host_load1
    WHERE val > 10 and ts >= now() - '1 minutes'::INTERVAL

Assume the query result is not empty and looks like this:

label_collector	label_host	val
collector1	host1	12
collector2	host2	15

This will generate two notifications.

The first notification will have the following labels and annotations:

• Labels:
  • collector: collector1
  • host: host1
  • the labels defined in the LABELS clause
• Annotations:
  • val: 12
  • the annotations defined in the ANNOTATIONS clause

The second notification will have the following labels and annotations:

• Labels:
  • collector: collector2
  • host: host2
  • the labels defined in the LABELS clause
• Annotations:
  • val: 15
  • the annotations defined in the ANNOTATIONS clause

Interval expression

It indicates how often the query is executed. e.g., '5 minute'::INTERVAL, '1 hour'::INTERVAL etc. For more details, see interval-type.

Labels and Annotations clauses

The LABELS and ANNOTATIONS clauses allow you to attach static key-value pairs to the notification messages sent by Trigger. These can be used to provide additional context or metadata about the Trigger.

• LABELS: serve as labels for Alertmanager routing, grouping, and inhibition.
• ANNOTATIONS: typically for human-readable descriptions.

Notify clause

The NOTIFY clause allows you to specify one or more notification channels.

Currently, GreptimeDB supports the following notification channel:

Webhook

The webhook channel will send HTTP requests to a specified URL when the Trigger fires. The payload of the http request is compatible with Prometheus Alertmanager, which means you can use GreptimeDB's Trigger with Prometheus Alertmanager without any extra glue code.

The optional WITH clause allows you to specify additional parameters:

• timeout: The timeout for the HTTP request, e.g., timeout='1m'.

Show Triggers

Show all triggers:

SHOW TRIGGERS;

Show triggers by like pattern:

SHOW TRIGGERS LIKE '<pattern>';

For example:

SHOW TRIGGERS LIKE 'load%';

Show triggers by where condition:

SHOW TRIGGERS WHERE <condition>;

For example:

SHOW TRIGGERS WHERE name = 'load1_monitor';

Drop Trigger

To delete a trigger, use the following DROP TRIGGER clause:

DROP TRIGGER [IF EXISTS] <trigger-name>;

For example:

DROP TRIGGER IF EXISTS load1_monitor;