Nicolas Ferrandini Nicolas Ferrandini - 1 month ago 11
Python Question

AWS Python Lambda with Oracle - OID Generation Failed

I'm trying to connect to an Oracle DB using AWS Lambda Python code.

My code is below:

import sys, os
import cx_Oracle
import traceback

def main_handler(event, context):

# Enter your database connection details here
host = "server_ip_or_name"
port = 1521
sid = "server_sid"
username = "myusername"
password = "mypassword"

try:
dsn = cx_Oracle.makedsn(host, port, sid)
print dsn
connection = cx_Oracle.Connection("%s/%s@%s" % (username, password, dsn))
cursor = connection.cursor()
cursor.execute("select 1 / 0 from dual")
except cx_Oracle.DatabaseError, exc:
error, = exc.args
print >> sys.stderr, "Oracle-Error-Code:", error.code
print >> sys.stderr, "Oracle-Error-Message:", error.message
tb = traceback.format_exc()
else:
tb = "No error"
finally:
print tb


if __name__ == "__main__":
main_handler(sys.argv[0], None)


If have already added all dependencies in "lib" folder, thanks to AWS Python Lambda with Oracle

When running this code, I'm getting:
DatabaseError: ORA-21561: OID generation failed

i've tried to connect using IP of the Oracle server and the name: same error.

Here is the output of the error

Oracle-Error-Code: 21561
Oracle-Error-Message: ORA-21561: OID generation failed

Traceback (most recent call last):
File "/var/task/main.py", line 20, in main_handler
connection = cx_Oracle.Connection("%s/%s@%s" % (username, password, dsn))
DatabaseError: ORA-21561: OID generation failed


For those who have successfully run the CX_Oracle in AWS Lambda Python, can you please help ?

Thanks

Answer

Ok, here is the explanation: Oracle has a funny behavior where if the hostname given by hostname can't be resolved, it will fail connecting to the DB. Fortunately, in Linux, one can override the DNS entry for a session by writing an alias file in /tmp, then setting the environment variable HOSTALIASES to that file.

So adding this code to my function help to generate this file, and now I can successfully connect:

f = open('/tmp/HOSTALIASES','w')
str_host = os.uname()[1]
f.write(str_host + ' localhost\n')
f.close()

Hope it can help someone else !

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