Before you start publishing messages, it is recommended that you call fedmsg.init(). This should be done from every Python thread you intend to publish messages from, and should be done early in your application’s initialization. The reason for this is that this call creates a thread-local zmq.Context and bind to a socket for publishing.


Since the network’s latency is not 0, it can take some time before a subscriber has set up its connection to the publishing socket. When a publishing socket has no subscribers, it simply drops the published message. Currently, the only way to avoid lost messages is to initialize the socket as early as you can.

To publish a message, call fedmsg.publish(). Your message should be a Python dictionary capable of being JSON-serialized. Additionally, any strings it contains should be a text type. That is, unicode in Python 2 and str in Python 3.

Publishing Through a Relay

It’s possible to avoid having each thread bind to a socket for publishing. To do so, you need to set up a fedmsg-relay service. Once it’s running, you need to set active to True, which causes publishing sockets to connect to the socket specified in relay_inbound.

Publishing Without ZeroMQ

fedmsg also supports publishing your messages via STOMP. Brokers that support STOMP include RabbitMQ and Apache ActiveMQ. Consult the STOMP Configuration for details on how to configure this.

Common Problems

There are a set of problems users commonly encounter when publishing messages, nearly all of them related to configuration. Check the logs to see if there are any helpful messages.

ZeroMQ Not Enabled

fedmsg supports publishing messages using protocols other than ZeroMQ. If you neglect to set zmq_enabled to True, fedmsg will attempt to publish the message with Moksha’s Hub. If the hub has not been initialized, you’ll receive an AttributeError when you call fedmsg.publish().

No Endpoints Available

Currently, unless you are publishing through a relay, you must declare a list of endpoints that fedmsg can bind to. Each Python thread, when fedmsg.init() is called, iterates through the list and attempts to bind to each address. If it is unable to bind to any address, an IOError is raised. The solution is to add more endpoints to the configuration.