MailerQ depends on RabbitMQ for message queueing. Before you can even start MailerQ, you first need a running RabbitMQ instance. The www.rabbitmq.com website has all the information you need for setting up RabbitMQ. We do however have some tips, tricks and recommendations for setting up RabbitMQ with MailerQ.
The RabbitMQ version that is installed in the repository of your operating system might be outdated. You really need a version that is up-to-date, because MailerQ uses a couple of RabbitMQ features that were only recently added. We therefore recommend downloading and installing RabbitMQ directly from the www.rabbitmq.com website instead of using the version that comes with your OS.
The RabbitMQ installation has to be at least version 3.3.1+ for MailerQ to be able to connect to it.
By default, RabbitMQ is installed with a user with login
guest and password
These are the login credentials that you have to include in the configuration file
of MailerQ. However, this guest/guest login only works for clients that connect
to RabbitMQ locally (from the same machine). If you run MailerQ and RabbitMQ on
different servers, the
guest/guest login does not work. Therefore, if you install
RabbitMQ and MailerQ on different machines, you either need to add a user with a
different name and password, or you should configure RabbitMQ to allow
logins from remote hosts as well.
To allow remote guest/guest logins, you can use the
loopback_users setting in the
RabbitMQ config file. By including this option in the RabbitMQ config file, you tell
RabbitMQ that it is ok for clients to login with
guest/guest, even if the connection
comes from a remote location. If you do include this setting, please make sure that
you also have a firewall running, because you do not want everyone from all over the
internet to connect to your RabbitMQ instance!
Just like MailerQ, RabbitMQ comes with a very nice web interface. However, this web interface is not enabled by default, and must be explicitly configured. We recommend doing this, because it is much easier to control RabbitMQ via a web browser, than with command line tools.
MailerQ not only uses RabbitMQ to fetch the messages that it is going to send, but also publish back the delivery results (if you have this configured). If you do not process these delivery results in time, the queues in RabbitMQ will get fuller and fuller and you run the risk that your RabbitMQ server runs out of resources (memory or disk space), which might crash the server. This can especially happen in a production environment, where many messages are published and consumed.
So, when you run MailerQ in production, do make sure that you have set up cronjobs or other scripts that periodically or continuously process the messages from the result queues.
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