flowchart LR
Broker[("broker")] -- sub --> D["mads dealer
PUSH bind :9093"]
D -- push --> W1["mads worker #1"]
D -- push --> W2["mads worker #2"]
D -- push --> W3["mads worker #3"]
W1 -- pub --> Broker
W2 -- pub --> Broker
W3 -- pub --> Broker
Commands: dealer / worker
command
cli
core
scaling
Abstract
mads dealer and mads worker together implement round-robin load balancing across multiple worker processes: one dealer fans a subscribed message stream out to any number of workers over a PUSH/PULL pair, layered on top of the normal broker pub/sub connection. This is the pattern to reach for when a single filter stage becomes a bottleneck and needs to run in parallel.
Synopsis
mads dealer [common options]
mads worker [common options] [plugin] # plugin must be a filter; default bridge.pluginDescription
Both are ordinary Agent subclasses with one extra socket each, layered on top of the normal broker pub/sub connection:
ZeroMQ’s PUSH socket round-robins fairly across every connected PULL peer, so adding another mads worker process (potentially on another machine) is enough to add parallelism — no coordination beyond both sides agreeing on dealer_address.
mads dealer
Subscribes like any agent (default sub_topic = ["publish", "spawner"]) and binds a PUSH socket at dealer_address (ini key, default tcp://*:9093). For each message received, it does two things: pushes the raw payload to whichever worker is next in the round-robin, and republishes the same JSON back to the broker under its own pub_topic (default dealer) — so the original message and its “dispatched” echo both appear on the network.
mads worker
Connects a PULL socket to dealer_address (default tcp://localhost:9093) and loads a filter plugin (default bridge.plugin, same default as mads filter). Each loop iteration: pulls the next payload from the dealer, runs it through the plugin’s load_data() then process(), and publishes the result back to the broker.
Warning
The topic passed to the plugin’s load_data() comes from the worker’s own plain broker receive() call in that same loop tick — a separate socket from the PULL side. Since the pulled payload and the plain-receive topic are serviced independently each iteration, the topic string is not guaranteed to correspond to the pulled payload’s real origin topic.
Options
Both take the same standard agent options: -n/--name, -i/--agent-id, -s/--settings, -S/--save-settings, --crypto (+ --keys_dir/--key_broker/--key_client/--auth_verbose), -v/--version, -h/--help. mads worker additionally takes a positional plugin path (any filter plugin; falls back to the ini attachment, then bridge.plugin, exactly like mads filter).