Alerts

Alerts define metrics for watching database data and if any metric exceeds its limit then alert is activated and further operation can be executed.

Metrics are configured - the SQL query for getting count of items and limit for checking.

Examples of alerts (also with follow-up operations):

• when count of failed messages for last 10 minutes exceeds 5 then sends email to administrators
• when count of messages which wait for response from external system for more then 5 minutes exceeds 10 then sends email to administrators

Alerts checking is scheduled operation that is determined by ohf.alerts.repeatTime configuration parameter - checking is executed every 5 minutes by default.

Alerts configuration

There are the following configuration possibilites:

• property files (default option)
• JMX

Properties alerts configuration

Alerts configuration uses the same model as rest of OpenHub framework, see External configuration model 

Property file configuration format and example (from application.properties):

###############################################################################
#  Alerts configuration
#
#   There the following property names:
#   - alerts.N.id: unique alert identification (if not defined then order number (=N) is used instead)
#   - alerts.N.limit: limit that must be exceeded to activate alert
#   - alerts.N.sql: SQL query that returns count of items for comparison with limit value
#   - [alerts.N.enabled]: if specified alert is enabled or disabled; enabled is by default
#   - [alerts.N.mail.subject]: notification (email, sms) subject; can be used Java Formatter placeholders (%s = alert ID)
#   - [alerts.N.mail.body]: notification (email, sms) body; can be used Java Formatter placeholders (%d = actual count, %d = limit)
#
###############################################################################

# checks if there is any waiting message that exceeds time limit for timeout
alerts.900.id=WAITING_MSG_ALERT
alerts.900.limit=0
alerts.900.sql=SELECT COUNT(*) FROM message WHERE state = 'WAITING_FOR_RES' AND last_update_timestamp < (current_timestamp - interval '3600 seconds')

JMX alerts configuration

JMX configuration allows change alert limits and enable/disable selected alerts.

Reaction to alert activation

There are listeners org.openhubframework.openhub.spi.alerts.AlertListener which are called when specified alert is activated. 

There is default org.openhubframework.openhub.core.alerts.EmailAlertListenerSupport implementation that  sends email notifications to admin emails.

If you want to implement more actions and you can implement AlertListener or extends default implementation EmailAlertListenerSupport.