def require_one(self,
key,
host=None,
strict=True,
reverse=False,
dirty=False):
"""Require a resource, returning a scalar.
For the parameters, see :py:meth:`require`.
:return: The matching resource that was provided.
:rtype: object
This version returns a single value instead of a list. Also, if the
number of potential results is not exactly one, then an error will
be raised (which you should not catch). batou will notify you of this
as being an inconsistent configuration.
"""
resources = self.require(key, host, strict, reverse, dirty)
if len(resources) > 1:
raise KeyError(
'Expected only one result, got multiple for (key={}, host={})'.
format(key, host))
elif len(resources) == 0:
raise SilentConfigurationError()
return resources[0]
def call(*args, **kw):
output.annotate("rpc {}: {}(*{}, **{})".format(
self.host.fqdn, name, args, kw),
debug=True)
self.host.channel.send((name, args, kw))
while True:
message = self.host.channel.receive()
output.annotate("{}: message: {}".format(
self.host.fqdn, message),
debug=True)
type = message[0]
if type == "batou-result":
return message[1]
elif type == "batou-output":
_, output_cmd, args, kw = message
getattr(output, output_cmd)(*args, **kw)
elif type == "batou-configuration-error":
raise SilentConfigurationError()
elif type == "batou-deployment-error":
raise DeploymentError()
elif type == "batou-unknown-error":
output.error(message[1])
raise RuntimeError(
"{}: Remote exception encountered.".format(
self.host.fqdn))
elif type == "batou-error":
# Remote put out the details already.
raise RuntimeError(
"{}: Remote exception encountered.".format(
self.host.fqdn))
else:
raise RuntimeError("{}: Unknown message type {}".format(
self.host.fqdn, type))