[Hawkular-dev] [Alerts] Thoughts on the notification system

[Thomas Segismont]

Hi,

I've been thinking about the alert notification system lately.

What's the information needed to send a notification?
How to convert the information into text when a human is the recipient? 
How to configure the system?
How to make it fit into the Hawkular suite?

1. Contextual data

A notification has contextual data. Contextual data is comprised of:
- alert definition data
- data involved in the trigger (for example metrics and availability values)

2. Notifier data

2.1 Who is the recipient?

Email: address
SMS: phone number

Sometimes the recipient is fixed (for example when sending email to a 
mailing-list).
Sometimes it should be picked from user information (for example when 
sending emails to a group of users)

This information depends on the alert definition, but a default should 
be configurable for convenience.

2.2 How should the message be sent?

Email: SMTP address/port and credentials
SMS: Web service HTTP URL and credentials

The information depends on the tenant (in rare cases, on the alert 
definition, but let's ignore the problem for now)

3. How should the message be formatted?

When a human is the recipient, information can be turned into text with 
a template engine (like freemarker).

Information depends on the alert definition, but a default should be 
configurable for convenience.

4. Configuration

Notifiers may expose REST endpoints (with standardized URIs)

- default config: /emailnotifier/configuration

- alert definition level config: /emailnotifier/configuration/1

Example:

{
     "to": ["paul at foobar.com", "alfred at foobar.com"],
     "cc": ["backoffice-mw-ops at foobar.com"],
     "subject": "Pool soon exhausted",
     "mode": "plaintext+html"
     "templates":
         [{
             name: "plaintext",
             uri: "/emailnotifier/configuration/1/templates/plaintext"
         },{
             name: "html",
             uri: "/emailnotifier/configuration/1/templates/html"
         }]
}

- template configs:

Example:

/emailnotifier/configuration/1/templates/plaintext
/emailnotifier/configuration/1/templates/html


I'm still not sure which component should be responsible of loading user 
information when a user (or a group of users) is selected as the recipient.

5. Process

- Alerts sends contextual data on the bus
- Notifier picks it up
- Notifier loads configuration for this alert definition or the default one
- Notifier applies the template (optional)
- Notifier sends email or invoke sender API

6. Storage

There needs to be some shared storage where to bind configuration and 
templates to alert definitions.


Comments?

Regards,
Thomas