COMPAS EVE

Event-based communication for the COMPAS framework.

>>> import compas_eve as eve
>>> pub = eve.Publisher("/hello_world")
>>> sub = eve.EchoSubscriber("/hello_world")
>>> sub.subscribe()
>>> for i in range(10):
...    pub.publish(dict(text=f"Hello World {i}"))

It is extremely easy to send messages around. COMPAS EVE supports different transport mechanisms to send messages between different threads, processes, computers, etc.

Installation

Install using pip:

    pip install compas_eve

Or using conda:

    conda install compas_eve

Supported features

• Publisher/subscriber communication model (N-to-N communication)
• In-process events
• MQTT support
• Zenoh support
• Extensible codec system for message serialization (JSON, Protocol Buffers)

Examples

In-process events

The simplest option is to use in-process events. This works for simple applications and allows to communicate between threads.

import compas_eve as eve

pub = eve.Publisher("/hello_world")
sub = eve.EchoSubscriber("/hello_world")
sub.subscribe()

for i in range(10):
    pub.publish(dict(text=f"Hello World {i}"))

MQTT

MQTT is a protocol that allows to send messages between different systems/computers. Using MQTT is very simple as well:

import compas_eve as eve
from compas_eve.mqtt import MqttTransport

tx = MqttTransport("broker.hivemq.com")
eve.set_default_transport(tx)

pub = eve.Publisher("/hello_world")
sub = eve.EchoSubscriber("/hello_world")
sub.subscribe()

for i in range(10):
    pub.publish(dict(text=f"Hello World {i}"))

This example shows how to send and receive from a single script, but running publishers and subscribers on different scripts, different processes, or even different computers will work the exact same way.

Zenoh

Apache Zenoh is a pub/sub/query protocol. In many ways, it is similar to MQTT but with some additional features and optimizations. COMPAS EVE also supports Zenoh as a transport protocol with an identical API to MQTT:

import compas_eve as eve
from compas_eve.zenoh import ZenohTransport

tx = ZenohTransport()
eve.set_default_transport(tx)

pub = eve.Publisher("/hello_world")
sub = eve.EchoSubscriber("/hello_world")
sub.subscribe()

for i in range(10):
    pub.publish(dict(text=f"Hello World {i}"))

Using different codecs

By default, COMPAS EVE uses JSON for message serialization. However, you can use different codecs for more efficient serialization:

import compas_eve as eve
from compas_eve import JsonMessageCodec
from compas_eve.codecs import ProtobufMessageCodec
from compas_eve.mqtt import MqttTransport

# Use JSON codec (default)
json_codec = JsonMessageCodec()
tx = MqttTransport("broker.hivemq.com", codec=json_codec)

# Or use Protocol Buffers for binary serialization (requires compas_pb)
pb_codec = ProtobufMessageCodec()
tx = MqttTransport("broker.hivemq.com", codec=pb_codec)

Usage from Rhinoceros 3D

It is possible to use the same code from within Rhino/Grasshopper.

To install compas_eve, use the the syntax # r: compas_eve at the top of any Python 3.x script in Rhino/Grasshopper.