Using Oracle database drivers in Windows containers

May 18, 2019

 modernize-legacy-app containers windows  mta  oracle  docker  windows

TL;TR; Head to oracle-drivers folder to view examples of Dockerfiles how to install a specific Oracle driver inside of a Windows container.

Challenge

In the field I’m seeing a fair number of legacy Windows applications using Oracle database. Many examples I came across had either full blown Oracle client installed or Oracle client runtime version installed. Here are a few patterns I’ve seen the most:

  • Legacy apps built on-demand and customers don’t have any source code for them.
  • Oracle client with necessary drivers gets installed by means of executing EXE distro of the client.
  • Apps written in 2000’s use quite old Oracle client versions (e.g. versions 8.x/9.x).
  • Apps hosted on Win 2000/2003 use 32-bit versions of drivers (e.g. ODBC, OLEDB).
  • Oracle drivers have dependency on Visual C++ Redistributable Package that Microsoft provides.

Obvious question and therefore a challenge is to figure out how to containerize legacy applications that depend on old versions of Oracle drivers without necessity to change the code.

Approach

If there is ability to use Oracle Managed.NET driver for .NET apps, by all means DO. It simplifies installation and dependency graph for it is a lot lighter than for native Oracle drivers.

There are several different Oracle drivers packed into Oracle client distro. For instance, odp.net2, odp.net4, asp.net2, asp.net4, odbc, oledb, etc. While it’s possible to execute Oracle client EXE distro and install entire collection of drivers, standard recommended practice tells us to install only what’s necessary for the app and nothing more. There are 2 main issues I ran into:

  • Minimum Windows version for Windows containers is Windows Server 2016 (WS2016), therefore the minimum version of Oracle client that is supported in Windows containers is Oracle client 12.
  • Oracle client drivers won’t work without proper version of VC++ Redistributable Package.

Therefore, your course of action should be:

  • download and install VC++ Redistributable Package
    • Oracle client 12.2 has dependency on VC++ 2013 redist package (x86 ver and x64 ver). Make sure to check installation instructions for a particular Oracle client to determine correct version of the dependency package
    • keep in mind that there are 64-bit and 32-bit drivers which require corresponding version of VC++ redist package
    • download and install necessary Oracle client driver

I was able to containerize legacy app with dependency on older Oracle driver versions by installing appropriate Oracle driver from Oracle client 12. I anticipate that in some cases it may not be as simple as this but for me that’s all I had to do.

Installing ODP.NET/ASP.NET driver

This example Dockerfile is parametrized to allow installation of Oracle drivers for different versions of odp.net and asp.net.

ASP.NET Dockerfile

ODP.NET Dockerfile

Installing ODBC driver

This example Dockerfile is parametrized to allow installation of ODBC driver for specified version of Oracle client.

ODBC Dockerfile

Installing OLEDB driver

OLEDB Dockerfile

Additional remarks

One issue I ran into was related to anti-virus and threat detection software that blocked MSI packages from being installed inside of the containers. In my case the offender was Semantec Endpoint Protection (SEP) software. The solution was to whitelist msiexec.exe process in SEP. You can find more details around the issue and troubleshooting Docker file on MSFT forum.

Troubleshooting & testing

Here are a few troubleshooting and testing techniques I employed while researching this topic.

determine whether VC++ redist package was installed correctly

# escape=`
.....
RUN `
  # check whether vc redist 2013 assemblies were installed
  # check physical path for x86 version
  gci -Path C:\Windows\syswow64\* -Include msvcp120*; `
  # check physical path for x64 version
  gci -Path C:\Windows\system32\* -Include msvcp120*; `
  # check Windows registry for VC++ redist package bits
  reg query hklm /s /f msvcp120;

verify ODBC driver was installed and ODBC DSN created

# escape=`
.....
RUN `
  # get all ODBC drivers installed in the system
  get-odbcdriver | format-table; `
  # get all ODBC DSNs
  get-odbcdsn;

enable error propagation to browser for Classic ASP apps

Classic ASP framework requires a setting scriptErrorToBrowser to be turned on in order to view the error that may occur in the application. Here is example how one can turn that setting on:

Install-WindowsFeature Web-ASP
Set-WebConfigurationProperty '/system.webServer/asp' -Name scriptErrorSentToBrowser -Value true -Force

Resources

 Toc
 Tags
 Related