以下是一个示例代码，展示了如何使用Buildbot检测工作机是否闲置：

from buildbot.schedulers.basic import AnyBranchScheduler
from buildbot.process.factory import BuildFactory
from buildbot.steps.source import Git
from buildbot.steps.shell import ShellCommand

def create_build_factory():
    factory = BuildFactory()
    factory.addStep(Git(repourl='https://github.com/example/repo.git', mode='full'))
    factory.addStep(ShellCommand(command=['make']))
    return factory

def create_builders():
    builders = []
    for i in range(5):  # 创建5个Builder，每个Builder对应一个工作机
        factory = create_build_factory()
        builders.append({'name': f'Builder{i}', 'factory': factory})
    return builders

builders = create_builders()

c = BuildmasterConfig = {}
c['builders'] = builders
c['schedulers'] = []

# 创建一个定时触发的Scheduler
c['schedulers'].append(AnyBranchScheduler(
    name="scheduler",
    treeStableTimer=60,
    builderNames=[builder['name'] for builder in builders]
))

# 添加一个Worker
c['workers'] = []
c['workers'].append({'name': 'worker', 'password': 'pass'})

# 创建一个状态改变的Hook，用于监测工作机是否闲置
def on_builder_change(build):
    worker_name = build.worker.name
    is_idle = build.getBuildStatus() == "idle"
    print(f"Worker {worker_name} is idle: {is_idle}")

c['change_source'] = []
c['change_source'].append({
    'name': 'hook',
    'hookURL': 'http://localhost:8010/change_hook',
    'change_hook_dialects': {'buildbot': True},
    'change_hook_queue_name': 'buildbot-worker-hook',
    'change_hook_timeout': 10,
    'change_hook_extra_headers': {},
    'change_hook_extra_params': {},
    'change_hook_api_version': 2,
    'change_hook_secret': 'secret',
    'change_hook_worker_change_hook': on_builder_change
})

上述代码中，我们创建了5个Builder，每个Builder对应一个工作机。然后，我们创建了一个定时触发的Scheduler，每隔60秒触发一次构建。在Buildbot中，工作机状态会在构建过程中发生变化，可以通过注册一个状态改变的Hook来监测工作机是否闲置。在示例代码中，我们定义了一个on_builder_change函数作为Hook的回调函数，用于处理工作机状态的改变。当工作机状态变为"idle"时，表示工作机闲置，我们可以在回调函数中执行相应的操作。