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happy-simulator

A discrete-event simulation library for Python 3.13+, built for modeling distributed systems, queuing networks, and complex real-world processes.

  • Event-Driven Core

    Central EventHeap schedules and executes Event objects through Entity handlers. Generators let you express delays with yield.

  • 200+ Components

    Queues, servers, networks, consensus protocols, storage engines, industrial processes, behavioral models, and more.

  • Observability Built In

    Data, Probe, LatencyTracker, SimulationSummary, and bucketed time-series analysis out of the box.

  • Visual Debugger

    Browser-based dashboard with entity graphs, charts, event logs, and step/play/pause controls.

Quick Example

from happysimulator import (
    Simulation, Event, Entity, Instant, Source, Sink,
)

class Server(Entity):
    def __init__(self, name, downstream):
        super().__init__(name)
        self.downstream = downstream

    def handle_event(self, event):
        yield 0.1  # simulate 100ms processing
        return [Event(time=self.now, event_type="Done", target=self.downstream)]

sink = Sink()
server = Server("server", downstream=sink)
source = Source.constant(rate=5, target=server)

sim = Simulation(
    entities=[source, server, sink],
    duration=10,
)
summary = sim.run()
print(f"Processed {sink.events_received} requests")
print(f"Avg latency: {sink.latency_stats()['avg']:.3f}s")

Next Steps