在要开始debug的地方导入pdb：

class KeypairAPI(base.Base):    """Sub-set of the Compute Manager API for managing key pairs."""    def __init__(self, **kwargs):        super(KeypairAPI, self).__init__(**kwargs)    def _validate_keypair_name(self, context, user_id, key_name):        import pdb; pdb.set_trace()               safechars = "_- " + string.digits + string.ascii_letters        clean_value = "".join(x for x in key_name if x in safechars)

 

然后触发该代码，如执行cli命令等，然后用screen打开后台就会看到如下：

..2013-03-26 19:56:26 71243 DEBUG nova.utils [-] Reloading cached file /etc/nova/policy.json read_cached_file /usr/lib/python2.6/site-packages/nova/uti12013-03-26 19:56:27 INFO nova.api.openstack.wsgi [req-9ef1fd31-0cec-4465-894a-f1ae0fa9a77e 320ce46de7e24a75a7ff8906d7355ff7 57ff99aae24b4035b52177a72s> /usr/lib/python2.6/site-packages/nova/compute/api.py(2198)_validate_keypair_name()-> safechars = "_- " + string.digits + string.ascii_letters(Pdb) (Pdb)  n> /usr/lib/python2.6/site-packages/nova/compute/api.py(2199)_validate_keypair_name()-> clean_value = "".join(x for x in key_name if x in safechars)(Pdb) safechars '_- 0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ' (Pdb) (Pdb) quit

debug完后输入quit继续运行。

debug好之后不要忘了Remove the debugging fragment from the source file. Start the server daemon gracefully —

 

ref： https://kashyapc.com/2013/03/27/debugging-nova-a-small-illustration-with-pdb/