Function Simulators

This section is dedicated to showcase a selection of pre-defined function simulators and gives details on how to implement one yourself.

Attention

Make sure you’ve familiarized yourself with Resources and Function simulators.

As our work is heavily influenced by the design and architecture of OpenFaaS, we provide two implementations of FunctionSimulator that model the behavior of forking and HTTP modes (see Watchdog modes).

The implementations are located in sim/faas/watchdogs.py and can be imported with:

from sim.faas import ForkingWatchdog, HTTPWatchdog

The abstract class that represents the general Watchdog concept looks like this:

class Watchdog(FunctionSimulator):

def claim_resources(self, env: Environment, replica: FunctionReplica, request: FunctionRequest): ...

def release_resources(self, env: Environment, replica: FunctionReplica, request: FunctionRequest): ...

def execute(self, env: Environment, replica: FunctionReplica, request: FunctionRequest): ...

The HTTPWatchdog uses a queuing mechanism to simulate works and claims resources after the request received a token (i.e., a worker is available). The ForkingWatchdog claims and executes each request immediately without further delay.

Attention

When using the ForkingWatchdog make sure that you limit manually the requests due to RAM usage for each fork.

The following figure shows the log events that happen during the execution with the HTTPWatchdog and also depicts the interaction between different system components.