Email Notifications

Often it is useful to send email notifications out to certain folks when certain things occur or are noticed within the business logic. Rattail assumes that you might define any number of such events for which email should be sent out, and of course that you may want different recipients etc. for each event. With this in mind, the following email subsystem exists.

From Code

The Python code is listed before the configuration syntax, as it best illustrates the reasoning behind the config syntax. Here is a simplistic notification example:

from rattail.mail import send_email

def my_business_logic(config, yesterday_sales):
    max_sales = config.get_int('myapp', 'max_sales')
    if yesterday_sales > max_sales:
        send_email(config, 'sales_max_broken', {'sales': yesterday_sales})

Here also is the API doc for rattail.mail.send_email().

The point here is that send_email() should require nothing more than a handle on the current configuration object (which should always be available in some direct way), a “key” to distinguish the particular type of event for which the email is being sent, and an optional dictionary to be used as template context when rendering the email body.

Configuration

There are really three different aspects to the email configuration.

• Meta Configuration - transcends “types” of email notification
• Generic Configuration - common to all types of email notification
• Specific Configuration - unique to a particular type of email notification

Note that all configuration for this system will fall under the [rattail.mail]] section within your config file(s).

Meta Configuration

This aspect of configuration consists of settings which have nothing to do with the “type” of email notification involved. Instead of listing and describing them separately (for now), here is a config snippet which defines each:

[rattail.mail

smtp.server = localhost
smtp.username = mymailuser
smtp.password = mymailpass

templates =
        rattail:templates/email
        myproject:templates/email

Todo

Need to explain current limitations of SMTP authentication.

Todo

Need to properly explain email template path setting.

Generic Configuration

This aspect of configuration consists of settings which may (but need not be) overridden for any specific “type” of email notification. That is, they provide the default value if no specific override exists. Again, here is a config snippet which defines each:

[rattail.mail]

default.from = Rattail <rattail@example.com>

default.to =
     "Admins <admin@example.com>"
     "Managers" <manager@example.com>"

default.subject = [Rattail] Notification

Note that the “from” address is interpreted as a single address in all cases, and therefore does not require quotes; same goes for the subject. However the “to” address does require quotes around each individual address within what may (but need not be) a list.

Note also that it is generally assumed that you will define each of the settings above; this makes optional all Specific Configuration (below).

Specific Configuration

These are settings which override those described in Generic Configuration (above), and are specific to a particular “type” of email notification.

Each “type” of notification must have a unique “key” by which it will be distinguished. This key is then leveraged within the config syntax to define settings specific to the type. For instance, if there is a key “foo”, then this might be valid config for the “foo” notification type:

[rattail.mail]

foo.from = Rattail Foo Alerts <rattail-foo@example.com>

foo.to = "Foo Interested Parties" <foo@example.com>"

foo.subject = [Rattail] Foo Is

It is important to note that the key (“foo” in this example) cannot be created by way of configuration alone. Business logic code essentially “invents” a new type of notification any time a call to rattail.mail.send_email() is made; the notification type will from then on be designated by the key argument provided to that function. Any config settings designated by a key for which no code will attempt to send email (i.e. “made-up” keys within the config file) will be ignored.

The key name should ideally be descriptive for humans’ sake; this will also help to ensure it is unique. Something like “sales_max_broken” is of course much better than “foo” in that regard. But again, one must ultimately consult the code to determine what key should be used for configuring which conceptual type of notification. The “default” key is reserved for Generic Configuration (above).

Note also that since it is assumed you will have already provided Generic Configuration, you need only override those settings for which the generic value will not suffice. For instance it is very common to override the recipients for a specific notification, but the sender address is overridden less often.