Python 测试 SSH 可用性的优雅方式
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原文地址: http://stackoverflow.com/questions/14236346/
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Elegant way to test SSH availability
提问by nightowl
I need a Python program I'm using to poll a remote server for SSH connectivity and notify when it is available. I am currently doing this using paramiko; attempt to connect, if failure, wait and retry until success or max retries. This works, but it's a bit clunky. Also paramiko seems to either connect or throw an error, so the only way I could see to do this was with a try/except block which is bad, bad, bad. Here is the method:
我需要一个 Python 程序来轮询远程服务器以进行 SSH 连接并在它可用时通知。我目前正在使用 paramiko 执行此操作；尝试连接，如果失败，等待并重试，直到成功或最大重试。这有效，但有点笨重。此外，paramiko 似乎要么连接要么抛出错误，所以我能看到的唯一方法是使用 try/except 块，它很糟糕，很糟糕，很糟糕。这是方法：
def check_ssh(self, ip, user, key_file, initial_wait=0, interval=0, retries=1):
ssh = paramiko.SSHClient()
ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
sleep(initial_wait)
for x in range(retries):
try:
ssh.connect(ip, username=user, key_filename=key_file)
return True
except Exception, e:
print e
sleep(interval)
return False
There must be a more elegant solution than this. Paramiko is my SSH library of choice but am open to any suggestions here.
必须有比这更优雅的解决方案。Paramiko 是我选择的 SSH 库，但我对这里的任何建议持开放态度。
To clarify, I want to avoid using try / except as a means to control the normal flow of code execution - it should be used for catching actual errors such as bad host key, invalid user etc.
澄清一下，我想避免使用 try / except 作为控制正常代码执行流程的手段——它应该用于捕获实际错误，例如主机密钥错误、用户无效等。
采纳答案by silvado
As mentioned in the comment by frb, a try ... exceptblock is a good approach to test availability of a specific service. You shouldn't use a "catch-all" exceptblock though, but limit it to the specific exceptions that occur if the service is unavailable.
正如 frb 的评论中提到的，try ... except块是测试特定服务可用性的好方法。不过，您不应使用“全能”except块，但应将其限制为服务不可用时发生的特定异常。
According to documentation, paramiko.SSHClient.connectmay throw different exceptions, depending on the problem that occured while connecting. If you want to catch all those, your try ... exceptblock would look like this:
根据文档，paramiko.SSHClient.connect可能会抛出不同的异常，具体取决于连接时发生的问题。如果您想捕获所有这些，您的try ... except块将如下所示：
try:
ssh.connect(ip, username=user, key_filename=key_file)
return True
except (BadHostKeyException, AuthenticationException,
SSHException, socket.error) as e:
print e
sleep(interval)
If just a subset of these exceptions is relevant to your case, put only those into the tuple after except.
如果这些异常中只有一部分与您的情况相关，请仅将这些异常放入except.
