Why does pyinstaller generated cx_oracle application work on fresh CentOS machine but not on one with Oracle client installed?

Question

I wrote a python application that uses cx_Oracle and then generates a pyinstaller bundle (folder/single executable). I should note it is on 64 bit linux. I have a custom spec file that includes the Oracle client libraries so everything that is needed is in the bundle.

When I run the bundled executable on a freshly installed CentOS 7.1 VM, (no Oracle software installed), the program connects to the database successfully and runs without error. However, when I install the bundled executable on another system that contains RHEL 7.2, and I try to run it, I get

Unable to acquire Oracle environment handle.

My understanding is this is due to an Oracle client installation that has some sort of conflict. I tried unsetting ORACLE_HOME on the machine giving me errors. It's almost as though the program is looking for the Oracle client libraries in a location other than in the location where I bundled the client files.

It seems like it should work on both machines or neither machine. I guess I'm not clear on how the Python application/cx_Oracle finds the Oracle client libraries. Again, it seems to have found them fine on a machine with a fresh operating system installation. Any ideas on why this is happening?

Answer 1

One thing that you may be running into is the fact that if you used the instant client RPMs when you built cx_Oracle an RPATH would have been burned into the shared library. You can examine its contents and change it using the chrpath command. You can use the special path $ORIGIN in the modified RPATH to specify a path relative to the shared library.

If an RPATH isn't the culprit, then you'll want to examine the output from the ldd command and see where it is looking and then adjust things to make it behave itself!