Question

I have a Django program that is connecting to an Oracle database. In my settings.py file I have this configuration:

DATABASES = {
  'default': {
    'ENGINE': 'django.db.backends.oracle',
    'NAME': 'xe',
    'USER': 'MY_USER_NAME',
    'PASSWORD': 'abcdefghijklmnopqrstuvwxyz',
    'HOST': 'db_server.example.com',
    'PORT': '1234',
  }
}

I received a strange error when attempting to load the website:

ORA-28547: connection to server failed, probable Oracle Net admin error

After further investigation, I sniffed the TCP traffic between the webserver and the database server. I discovered this text in the network communication, which I reformatted for this post:

(DESCRIPTION=
    (ADDRESS=
        (PROTOCOL=TCP)
        (HOST=1.2.3.4)
        (PORT=1234)
    )
    (CONNECT_DATA=
        (SID=xe)
        (CID=
            (PROGRAM=httpd@webserver_hostname)
            (HOST=webserver_hostname)
            (USER=apache)
        )
    )
)

So my question is: why is Django attempting to connect to the Oracle database with different credentials than the ones I specified? Notably, it is attempting to use user ‘apache’ instead of ‘MY_USER_NAME’. The database host IP, port, and SID are correct and what I specified. It just appears to be the user name that is different.

(As a side note, I suppose the password is transmitted separately in a later portion of the log in process?)

Answer 1

Installing the full Oracle client (with Administrator tools) seems to have solved the problem. There are some nuances to take care of though:

wsgi.py requires the location of ORACLE_HOME, as it is not passed in from the shell. In my case, this is what wsgi.py looks like:

import os, sys
sys.path.append('/var/www/')
os.environ['DJANGO_SETTINGS_MODULE'] = 'myapp.settings'
os.environ['ORACLE_HOME'] = '/client/oracle/product/11.2.0/db'
from django.core.wsgi import get_wsgi_application
application = get_wsgi_application()

In Oracle 11.2.0 client there is a bug with the library linking. To fix Oracle library linking:

1. Navigate to $ORACLE_HOME/lib (in my case, /client/oracle/product/11.2.0/db/lib/)
2. Remove file libexpat.so.1
3. As user oracle: create a symbolic link: libexpat.so.1 –> libexpat.so.1.5.2

Additionally, it is important to have the Linux loader set up properly. (Note: this is equivalent to setting LD_LIBRARY_PATH, but I think the following is a cleaner solution). Create a file /etc/ld.so.conf.d/oracle.conf with a single line entry to the Oracle Home library path. In my case, it’s /client/oracle/product/11.2.0/db/lib. Then run ldconfig. To verify that the loader is configured correctly you can check the shared object paths for cx_Oracle:

To find the file: as superuser, execute updatedb and then locate cx_Oracle.so | grep cx_Oracle\.so$

To test the file: ldd <path>

The output should look similar to this (below). If you see the phrase “not found” then something is wrong with the loader paths.

# ldd /usr/lib/python2.7/site-packages/cx_Oracle.so
    linux-gate.so.1 =>  (0xb775c000)
    libclntsh.so.11.1 => /client/oracle/product/11.2.0/db/lib/libclntsh.so.11.1 (0xb5a25000)
    libpython2.7.so.1.0 => /usr/lib/libpython2.7.so.1.0 (0xb588e000)
    libpthread.so.0 => /lib/libpthread.so.0 (0xb5873000)
    libc.so.6 => /lib/libc.so.6 (0xb56c2000)
    libnnz11.so => /client/oracle/product/11.2.0/db/lib/libnnz11.so (0xb5474000)
    libdl.so.2 => /lib/libdl.so.2 (0xb546f000)
    libm.so.6 => /lib/libm.so.6 (0xb5444000)
    libnsl.so.1 => /lib/libnsl.so.1 (0xb5429000)
    libaio.so.1 => /lib/libaio.so.1 (0xb5427000)
    libutil.so.1 => /lib/libutil.so.1 (0xb5422000)
    /lib/ld-linux.so.2 (0x487b9000)

For convenience, you’ll probably also want to create the file /etc/profile.d/oracle.sh with these contents (note, change ORACLE_HOME to your specific install path):

export ORACLE_HOME=/client/oracle/product/11.2.0/db
export PATH=$PATH:$ORACLE_HOME/bin

Reboot for these global environment variables to take effect.

After that, Oracle connections should work in any scenario. I hope this information helps others who’ve had trouble with Oracle!