infos = Information about the zeromqsend plugin is in keys below
infos/author = Thomas Wahringer waht@.nosp@m.libe.nosp@m.lektr.nosp@m.a.or.nosp@m.g
infos/licence = BSD
infos/provides = notification
infos/needs =
infos/recommends =
infos/placements = postgetstorage postcommit
infos/status = maintained unittest libc global experimental
infos/description = Sends notifications over ZeroMq publish sockets when a key is changed

This plugin is a notification plugin, which sends notifications using ZeroMq publish (ZMQ_PUB) sockets when the key database (KDB) has been modified. It is compatible with the sending zeromqrecv plugin.

See installation. The package is called libelektra5-zeromq.

libzmq3-dev (ZeroMQ C bindings > 3.2)

The recommended way is to globally mount the plugin together with the zeromqrecv plugin:

kdb global-mount zeromqsend zeromqrecv

This plugin is designed to be used as a transport plugin for Elektra's notification feature. Since ZeroMq creates threads for asynchronous I/O this plugin always operates asynchronously.

Since ZeroMQ sockets only provide a 1:n mapping (i.e. one publisher with many subscribers or one subscriber and many publishers) the zeromqsend and zeromqrecv plugins require a XPUB/XSUB endpoint. The kdb tool "hub-zeromq" provides these endpoints.

Transport Plugin

Mount this plugin globally with default settings to use it as sending transport plugin for Elektra's notification feature:

kdb global-mount zeromqsend

Configuration

This plugin supports the following configuration options when mounting:

endpoint: ZeroMQ XSUB or SUB socket to connect to. The ipc and tcp ZeroMQ transports are recommended. The default value is "tcp://localhost:6000".
connectTimeout: Timeout for establishing connections in milliseconds. The default value is "1000".
subscribeTimeout: Timeout for waiting for subscribers in milliseconds. The default value is "200".

Notification Format

The ZeroMQ transport plugins use the publish/subscribe sockets (ZMQ_PUB and ZMQ_SUB) for notification transport.

Each notification is a multipart message. The first part contains the type of change, the second part contains the name of the changed key.

Possible only current change is Commit.