CREATE ALERT

You can create alerts to monitor your streaming data and automatically trigger actions when specific conditions are met.

Syntax

CREATE [OR REPLACE] ALERT [IF NOT EXISTS] [database.]alert_name
BATCH <N> EVENTS WITH TIMEOUT <nUnit>
LIMIT <N> ALERTS PER <nUnit>
CALL <python_udf_name>
AS <select_query>

For example:

CREATE ALERT default.test
BATCH 10 EVENTS WITH TIMEOUT 5s
LIMIT 1 ALERTS PER 15s
CALL send_to_http
AS SELECT value FROM default.foo;

Limitations

• The alerts only run on the metadata leader node.
• The return value of the Python UDF is ignored.
• The select query cannot include any aggregation or JOIN.
• Check system.stream_state_log for the alert states or logs.
• The checkpoints of the alerts are available in system.alert_ckpt_log stream with the _tp_sn column.

Python UDF

You can import Python libraries and build the custom alert action via Python UDF. The return value doesn't matter. Here is an example to send events to a specific Slack channel via Slack webhook:

CREATE OR REPLACE FUNCTION alert_action_proton_new_star(actor string) RETURNS string LANGUAGE PYTHON AS $$
import json
import requests
def alert_action_proton_new_star(value):
    for i in range(len(value)):
        github_id=value[i]
        requests.post("https://hooks.slack.com/services/T123/B456/other_id", data=json.dumps({"text": f"New 🌟 for Timeplus Proton from https://github.com/{github_id}"}))
    return value
$$

Please note, similar to regular Python UDF, the input parameter of the Python UDF is an array, instead of a single event. The return value can be anything but you can return the input value, so that you can test the Python UDF via SELECT udf_name(input).

See also

• SHOW ALERTS - Show alerts
• DROP ALERT - Drop alerts