Troubleshooting¶
Just as with any authenticated network service, you may run into problems from time to time while connecting to CAS. These are some of the more common problems you may run across.
Unable to Connect¶
There are various reasons that you may not be able to connect to your CAS server. You may have an incorrect hostname or port number. There may be a firewall preventing you from reaching the CAS server. Not being able to connect to a server will result in a error that looks like the following.
In [1]: conn = swat.CAS(hostname, port)
. . .
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "swat/cas/connection.py", line 297, in __init__
raise SWATError(self._sw_error.getLastErrorMessage())
swat.exceptions.SWATError: Could not connect to 'my-cas' on port 5570.
If you have verified that the server is running on that host and port, and that you are not being blocked, another possible reason for failure to connect is that the CAS server may be configured to use encrypted communication. For information on how to configure the Python SWAT client to communicate with CAS servers over encrypted connections, see Encryption (SSL).
Note
Beginning in SAS Viya 3.3, encrypted communication is enabled in the server by default.
Missing Linux Library Dependencies¶
SWAT uses various shared libraries commonly available on Linux machines. If you are missing a shared library that SWAT requires, you may see a message such as the following when creating a CAS connection.
In [1]: conn = swat.CAS(hostname, port)
tkBoot failed: Cannot dlopen [tkmk.so] : [libnuma.so.1: cannot open shared object file: No such file or directory]
This particular error can be solved by installing the numactl package of your Linux distribution. If you do not have system administrator privileges, you can set an environment variable LD_LIBRARY_PATH to the location of a copy of libnuma.so.1. However, it is recommended that you contact your system administrator to install this library so that it will receive regular updates with the system.
Incorrect SAS TK Configuration¶
The following error can occur if you do not have the SAS TK system properly configured. Normally, the correct TK settings are applied when SWAT is loaded. However, if you are using an installation of the libraries in a separate directory, you may get errors if the correct files are not in that directory.
In [1]: conn = swat.CAS(hostname, port)
tkBoot failed: Cannot Locate [tkmk] in [/usr/local/lib/swat-tk:/opt/sas/viya/SASFoundation/sasexe/:
Could not get TK handle
---------------------------------------------------------------------------
. . .
SWATError Traceback (most recent call last)
<ipython-input-2-d18c0dfd66ee> in <module>()
----> 1 s = swat.CAS('my-cas', 12345)
connection.py in __init__(self, hostname, port, username, password, session,
locale, nworkers, name, authinfo, protocol, **kwargs)
225 self._sw_error = clib.SW_CASError(a2n(soptions))
226 except SystemError:
--> 227 raise SWATError('Could not create CAS object. Check your TK path setting.')
228
229 # Make the connection
SWATError: Could not create CAS object. Check your TK path setting.
To fix this issue, make sure that swat.options.tkpath is set to the location of the SAS TK libraries.
Unable to Import _pyXXswat¶
If you are creating a CAS connection and you get the following error, it generally means that you don’t have the SAS TK libraries or the Python extension installed. This can happen if you only installed the Python source version of SWAT (not the installer that bundles the SAS TK libraries) and you tried to connect to CAS using the binary protocol.
The source-only Python installer can only connect to the REST interface of CAS, so you must point CAS to a REST port rather than a binary port.
In [1]: conn = swat.CAS(hostname, port)
. . .
During handling of the above exception, another exception occurred:
ValueError Traceback (most recent call last)
<ipython-input-2-cb8d2ab92685> in <module>()
----> 1 swat.CAS('my-cas', 12345)
connection.py in __init__(self, hostname, port, username, password, session,
locale, nworkers, name, authinfo, protocol, **kwargs)
223 self._sw_error = rest.REST_CASError(a2n(soptions))
224 else:
--> 225 self._sw_error = clib.SW_CASError(a2n(soptions))
226 except SystemError:
227 raise SWATError('Could not create CAS object. Check your TK path setting.')
clib.py in SW_CASError(*args, **kwargs)
84 ''' Return a CASError (importing _pyswat as needed) '''
85 if _pyswat is None:
---> 86 _import_pyswat()
87 return _pyswat.SW_CASError(*args, **kwargs)
88
clib.py in _import_pyswat()
43 raise ValueError(('Could not import import %s. This is likely due to an '
44 'incorrect SAS TK path or an error while loading the SAS TK subsystem. '
---> 45 'You can try using the REST interface as an alternative.') % libname)
46
47
ValueError: Could not import import _py34swat. This is likely due to an incorrect SAS TK
path or an error while loading the SAS TK subsystem. You can try using the
REST interface as an alternative.
Refused Connection¶
If you get an error saying that the connection was refused, you probably do not a CAS server running on that host or port, or you are behind a firewall that is preventing your from accessing that server.
In [1]: conn = swat.CAS('my-cas', 12345)
ERROR: The TCP/IP tcpSockConnect support routine failed with error 61 (The connection was refused.).
ERROR: Failed to connect to host 'my-cas', port 12345.
. . .
During handling of the above exception, another exception occurred:
SWATError Traceback (most recent call last)
<ipython-input-3-404a7919d58a> in <module>()
----> 1 conn = swat.CAS('my-cas', 12345)
cas/connection.py in __init__(self, hostname, port, username, password, session,
locale, nworkers, name, authinfo, protocol, **kwargs)
259 raise SystemError
260 except SystemError:
--> 261 raise SWATError(self._sw_error.getLastErrorMessage())
262
263 errorcheck(self._sw_connection.setZeroIndexedParameters(), self._sw_connection)
SWATError: Could not connect to 'my-cas' on port 12345.
Authentication Issues¶
Authentication problems can occur for many reasons. The examples below show two possible issues. The first one is an issue with the Authinfo file that contains the passwords. It requires the file permissions to be readable by the owner only. In this case, the Authinfo file was readable by others, which is invalid.
Other issues that can occur with an Authinfo file include not having a hostname and port that matches the one used in the CAS constructor or simply having the incorrect (possibly outdated) password in the file. The second code sample below shows the error for an incorrect password.
In [1]: conn = swat.CAS('my-cas', 12345)
WARNING: Incorrect permissions on netrc/authinfo file.
ERROR: Kerberos initialization failed. Your credential cache is either expired or missing.
---------------------------------------------------------------------------
SystemError Traceback (most recent call last)
connection.py in__init__(self, hostname, port, username, password, session,
locale, nworkers, name, authinfo, protocol, **kwargs)
256 a2n(soptions),
--> 257 self._sw_error)
258 if self._sw_connection is None:
. . .
SWATError: Could not connect to 'my-cas' on port 12345.
In [1]: conn = swat.CAS('my-cas', 12345)
ERROR: Connection failed. Server returned: Authentication failed: Access denied.
---------------------------------------------------------------------------
SystemError Traceback (most recent call last)
connection.py in __init__(self, hostname, port, username, password, session,
locale, nworkers, name, authinfo, protocol, **kwargs)
256 a2n(soptions),
--> 257 self._sw_error)
258 if self._sw_connection is None:
. . .
SWATError: Could not connect to 'my-cas' on port 12345.
UnicodeEncodeError in Windows Console¶
If you attempt to print content from a CAS action that contains UTF-8 encoded characters, you may encounter an error like the following:
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "c:\anaconda3\lib\encodings\cp437.py", line 19, in encode
return codecs.charmap_encode(input,self.errors,encoding_map)[0]
UnicodeEncodeError: 'charmap' codec can't encode characters in position 525-526: character maps to <undefined>
This can happen if the encoding in your Windows console is set to an encoding that can’t handle the characters in the CAS output. There are a few solutions to this issue.
Upgrade to Python 3.6. Python 3.6 includes a fix that will allow the characters to be displayed properly.
Run ‘chcp 65001’ in the console before executing your Python code. This will change the codepage in the console to one that will support the characters.
Install the win-unicode-console package and follow the instructions to enable it.