EmailService

Email sender using Mailgun.

In your config.exs file:

config :service_mailer, ServiceMailer.Mailer,
  adapter: Bamboo.MailgunAdapter,
  domain: System.get_env("MAILGUN_DOMAIN"),
  api_key: System.get_env("MAILGUN_API_KEY"),
  from_email: System.get_env("EMAIL")

config :consumer, :rabbitmq_config,
  host: System.get_env("QUEUE_HOST"), # "guest" as default
  host: System.get_env("QUEUE_PASSWORD"), # "guest" as default
  queue: System.get_env("QUEUE_NAME"),
  exchange: System.get_env("QUEUE_EXCHANGE") || "",
  consumers: 10

config :consumer, :pool_config,
  pool_name: :connection_pool,
  name: {:local, :connection_pool},
  worker_module: Consumer.ConnectionWorker,
  size: 5,
  max_overflow: 0

Sending emails

Templates

# start the REST server
$> iex -S mix phx.server

send a JSON POST request to /emails with "template" as attribute, in this case we are sending an email with template welcome and name: Simon.

$> curl -X POST \
  http://localhost:4000/api/emails \
  -H 'content-type: application/json' \
  -d '{
    "to": "user@example.com",
    "subject": "Welcome Email",
    "template": "welcome",
    "assigns": { "name": "Simon" }
  }'

HTML Body

or if just want to send the email directly you can use the body attribute

$> curl -X POST \
  http://localhost:4000/api/emails \
  -H 'content-type: application/json' \
  -d '{
    "to": "user@example.com",
    "subject": "Welcome Email",
    "body": "<html><body><h1>Hello World!</h1></body></html>",
  }'

Queue

We are using a RabbitMQ queue to consume the emails.

NOTE You must have the queue already configured an pass those params as part of the :rabbitmq_config application config.

For all the config options please refer to AMQP

Setting up a RabbitMQ with docker

# pull RabbitMQ image from docker
$> docker pull rabbitmq:3.7.7-management
# run docker in background
# name the container
# remove container if already exists
# attach default port between the container and your laptop
# attach default management port between the container and your laptop
# start rabbitmq with management console
$> docker run --detach --rm --hostname bunny --name roger_rabbit -p 5672:5672 -p 15672:15672 rabbitmq:3.7.7-management
# if you need to stop the container
$> docker stop roger_rabbit
# if you need to remove the container manually
$> docker container rm roger_rabbit

Now you can go to http://localhost:15672/# configure your queues and send an email test

Queue Consumer architecture

We are going to have a pool of connections to rabbitmq and a number of Consumers for the connection pool, each consumer is going to grab a channel to RabbitMQ, and is going to mark itself as a consumer. when there is an error we are going to reject and requeue the email for latter processing. if everything is ok we are going to ACK rabbitmq telling the email was successfully processed.

With this architecture you can scale to thousands of open channels to rabbitmq scaling pretty well, its also resilient and fault tolerant.

Sending Emails from the command line

# you have to go to the service mailer app in order to build the script, if not
# you are going to get ** (Mix) Building escripts for umbrella projects is unsupported
$> cd apps/service_mailer
$> mix escript.build
$> ./service_mailer --to "user@example.com" --subject "Welcome Email" --template "welcome" --assigns "name::Simon,username::fakeuser"
# or
$> ./service_mailer --to "user@example.com" --subject "Welcome Email" --body "<html><body><h1>Hello World!</h1></body></html>"

You can also publish emails to the queue

what it does is start a connection pool parse the JSON email metadata, and publish it to the specified queue and exchange via application config.

$> cd apps/consumer
$> mix escript.build
$> ./produce --email '{ "to": "user@example.com", "subject": "Welcome Email", "body": "<html><body><h1>Hello World!</h1></body></html>" }'

TODO

try to build the binaries into the root directory for ease of use

sescobb27 / ex_email_service