PostgreSQL LISTEN Exchange

A RabbitMQ exchange type that translates PostgreSQL NOTIFY messages to AMQP messages and publishes them to bound queues. The PostgreSQL NOTIFY message channel is used as the routing key for the message using direct exchange style routing mechanics.

Example

To publish Postgres notifications as AMQP messages into queues bound to a x-pgsql-listen exchange with a binding key of test, run the following command in psql:

postgres=# NOTIFY test, 'This is a test';

Installation

Extract the contents of the release zip file into your RabbitMQ plugins directory. Once extracted, run rabbitmq-plugins enable pgsql_listen_exchange.

Configuration

Argument Based Configuration

To connect to PostgreSQL using something other than the default pgsql://postgres@localhost:5432/postgres connection, you can add arguments when declaring the exchange:

Setting	Description	Data Type
x-host	The PostgreSQL server hostname	String
x-port	The port to connect on	Number
x-dbname	The database name to connect to	String
x-user	The user to connect as	String
x-password	The password to use when connecting	String

Policy Based Configuration

To apply configuration via a policy, the following settings are available:

Setting	Description	Data Type
pgsql-listen-host	The PostgreSQL server hostname	String
pgsql-listen-port	The port to connect on	Number
pgsql-listen-dbname	The database name to connect to	String
pgsql-listen-user	The user to connect as	String
pgsql-listen-password	The password to use when connecting	String

Configuration in rabbitmq.config

You can also change the default connection values in the rabbitmq.config file:

Setting	Description	Data Type	Default Value
host	The PostgreSQL server hostname	list	"localhost"
port	The port to connect on	integer	5432
dbname	The database name to connect to	list	"postgres"
user	The user to connect as	list	"postgres"
password	The password to use when connecting	list	""

Example rabbitmq.config

[{pgsql_listen_exchange,
  [
    {host, "localhost"},
    {port, 5432},
    {dbname, "postgres"},
    {user, "postgres"},
    {password, ""}
  ]}
].

Message Properties

The exchange will automatically add the following properties to messages:

Property	Value
app_id	pgsql-listen-exchange
headers	See "Headers Properties Values" table below
timestamp	The UNIX epoch timestamp of the publishing server

Headers Property Values

The following table details the values of the headers property that is set on each message.

Key	Value
pgsql-channel	The PostgreSQL notification channel
pgsql-server	The host and port of the PostgreSQL server
source-exchange	The pgsql-listen-exchange that the notification was received by

Specifying Other Properties

In addition to the automatically set message properties, the exchange can set configured message properties. To set one of the supported message properties, specify the property name and value when binding to the exchange. For example, to set the content_type property, specify content_type and the value it should be set to when binding a queue to the exchange. The following message properties are supported:

Property	Data Type
content_encoding	String
content_type	String
delivery_mode	Number
priority	Number
reply_to	String
type	String

Building

Steps to custom build a version of the pgsql-listen-exchange plugin follow the development environment instructions at https://www.rabbitmq.com/build-server.html#prerequisites and then run the following:

make tests
make dist
zip -r pgsql-listen-exchange.zip plugins/epgsql-* plugins/pgsql-listen-exchange-*

Unzip that file into the plugins directory for RabbitMQ and enable as you would any other plugin.