Passing LD_PRELOAD to apache 2.4 for mod_wsgi

Question

I can't adapt this question for mod_wsgi.

I have a python flask application that uses gdal. I start it up the following way:

LD_PRELOAD=/opt/gdal-custom/lib/libgdal.so.1 PYTHONPATH=../somemodules/ scl enable python27 "source ../python27/bin/activate; python flaskapp.py"

However, I'd like to host it in mod_wsgi. Doing LD_PRELOAD=/opt/gdal-custom/lib/libgdal.so.1 service httpd24-httpd restart doesn't seem to work. Neither does setting the following in my apache configuration:

SetEnv LD_PRELOAD /opt/gdal-custom/lib/libgdal.so.1

LoadModule wsgi_module modules/mod_wsgi.so

WSGIPythonHome /opt/rh/httpd24/root/var/www/wsgi-virtualenv

WSGIPythonPath /opt/rh/httpd24/root/var/www/AppFolder:/opt/rh/httpd24/root/var/www/SomeModules

WSGIScriptAlias /AppFolder /opt/rh/httpd24/root/var/www/AppFolder/app.wsgi

<Directory /var/www/AppFolder>
AllowOverride none
Require all granted
</Directory>

Here is the output of ldd:

(wsgi-virtualenv)ldd /opt/rh/httpd24/root/var/www/wsgi-virtualenv/lib/python2.7/site-packages/GDAL-1.11.2-py2.7-linux-x86_64.egg/osgeo/_gdal.so
    linux-vdso.so.1 =>  (0x00007fffac9ff000)
    libpython2.7.so.1.0 => /opt/rh/python27/root/usr/lib64/libpython2.7.so.1.0 (0x00007fce43438000)
    libgdal.so.1 => /opt/gdal-custom/lib/libgdal.so.1 (0x00007fce42490000)
    libstdc++.so.6 => /usr/lib64/libstdc++.so.6 (0x00007fce42176000)
    libm.so.6 => /lib64/libm.so.6 (0x00007fce41ef2000)
    libgcc_s.so.1 => /lib64/libgcc_s.so.1 (0x00007fce41cdb000)
    libpthread.so.0 => /lib64/libpthread.so.0 (0x00007fce41abe000)
    libc.so.6 => /lib64/libc.so.6 (0x00007fce4172a000)
    libdl.so.2 => /lib64/libdl.so.2 (0x00007fce41525000)
    libutil.so.1 => /lib64/libutil.so.1 (0x00007fce41322000)
    libfreexl.so.1 => /usr/lib64/libfreexl.so.1 (0x00007fce41119000)
    libgeos_c.so.1 => /usr/lib64/libgeos_c.so.1 (0x00007fce40ef2000)
    libsqlite3.so.0 => /usr/lib64/libsqlite3.so.0 (0x00007fce40c63000)
    libodbc.so.2 => /usr/lib64/libodbc.so.2 (0x00007fce409fc000)
    libodbcinst.so.2 => /usr/lib64/libodbcinst.so.2 (0x00007fce407ea000)
    libexpat.so.1 => /lib64/libexpat.so.1 (0x00007fce405c2000)
    libxerces-c-3.0.so => /usr/lib64/libxerces-c-3.0.so (0x00007fce40021000)
    libjasper.so.1 => /usr/lib64/libjasper.so.1 (0x00007fce3fdc7000)
    libnetcdf.so.6 => /usr/lib64/libnetcdf.so.6 (0x00007fce3fa82000)
    libhdf5.so.6 => /usr/lib64/libhdf5.so.6 (0x00007fce3f49a000)
    libogdi.so.3 => /usr/lib64/libogdi.so.3 (0x00007fce3f278000)
    libgif.so.4 => /usr/lib64/libgif.so.4 (0x00007fce3f06f000)
    libjpeg.so.62 => /usr/lib64/libjpeg.so.62 (0x00007fce3ee1f000)
    libgta.so.0 => /usr/lib64/libgta.so.0 (0x00007fce3ec14000)
    libpng12.so.0 => /usr/lib64/libpng12.so.0 (0x00007fce3e9ee000)
    libcfitsio.so.0 => /usr/lib64/libcfitsio.so.0 (0x00007fce3e63a000)
    libpq.so.5 => /usr/lib64/libpq.so.5 (0x00007fce3e411000)
    librt.so.1 => /lib64/librt.so.1 (0x00007fce3e209000)
    libpcre.so.0 => /lib64/libpcre.so.0 (0x00007fce3dfdd000)
    libcurl.so.4 => /usr/lib64/libcurl.so.4 (0x00007fce3dd88000)
    libxml2.so.2 => /usr/lib64/libxml2.so.2 (0x00007fce3da35000)
    libz.so.1 => /lib64/libz.so.1 (0x00007fce3d81f000)
    /lib64/ld-linux-x86-64.so.2 (0x0000003e73a00000)
    libgeos-3.4.2.so => /usr/lib64/libgeos-3.4.2.so (0x00007fce3d479000)
    libltdl.so.7 => /usr/lib64/libltdl.so.7 (0x00007fce3d270000)
    libnsl.so.1 => /lib64/libnsl.so.1 (0x00007fce3d056000)
    libhdf5_hl.so.6 => /usr/lib64/libhdf5_hl.so.6 (0x00007fce3ce24000)
    libproj.so.0 => /usr/lib64/libproj.so.0 (0x00007fce3cbd7000)
    libSM.so.6 => /usr/lib64/libSM.so.6 (0x00007fce3c9ce000)
    libICE.so.6 => /usr/lib64/libICE.so.6 (0x00007fce3c7b2000)
    libX11.so.6 => /usr/lib64/libX11.so.6 (0x00007fce3c475000)
    liblzma.so.0 => /usr/lib64/liblzma.so.0 (0x00007fce3c253000)
    libbz2.so.1 => /lib64/libbz2.so.1 (0x00007fce3c042000)
    libssl.so.10 => /usr/lib64/libssl.so.10 (0x00007fce3bdd6000)
    libcrypto.so.10 => /usr/lib64/libcrypto.so.10 (0x00007fce3b9f2000)
    libgssapi_krb5.so.2 => /lib64/libgssapi_krb5.so.2 (0x00007fce3b7ae000)
    libcrypt.so.1 => /lib64/libcrypt.so.1 (0x00007fce3b577000)
    libldap_r-2.4.so.2 => /lib64/libldap_r-2.4.so.2 (0x00007fce3b31e000)
    libidn.so.11 => /lib64/libidn.so.11 (0x00007fce3b0ec000)
    libldap-2.4.so.2 => /lib64/libldap-2.4.so.2 (0x00007fce3ae9c000)
    libkrb5.so.3 => /lib64/libkrb5.so.3 (0x00007fce3abb5000)
    libk5crypto.so.3 => /lib64/libk5crypto.so.3 (0x00007fce3a989000)
    libcom_err.so.2 => /lib64/libcom_err.so.2 (0x00007fce3a785000)
    libssl3.so => /usr/lib64/libssl3.so (0x00007fce3a545000)
    libsmime3.so => /usr/lib64/libsmime3.so (0x00007fce3a319000)
    libnss3.so => /usr/lib64/libnss3.so (0x00007fce39fda000)
    libnssutil3.so => /usr/lib64/libnssutil3.so (0x00007fce39dad000)
    libplds4.so => /lib64/libplds4.so (0x00007fce39ba9000)
    libplc4.so => /lib64/libplc4.so (0x00007fce399a4000)
    libnspr4.so => /lib64/libnspr4.so (0x00007fce39765000)
    libssh2.so.1 => /usr/lib64/libssh2.so.1 (0x00007fce3953d000)
    libuuid.so.1 => /lib64/libuuid.so.1 (0x00007fce39338000)
    libxcb.so.1 => /usr/lib64/libxcb.so.1 (0x00007fce3911a000)
    libkrb5support.so.0 => /lib64/libkrb5support.so.0 (0x00007fce38f0e000)
    libkeyutils.so.1 => /lib64/libkeyutils.so.1 (0x00007fce38d0b000)
    libresolv.so.2 => /lib64/libresolv.so.2 (0x00007fce38af1000)
    libfreebl3.so => /lib64/libfreebl3.so (0x00007fce388ed000)
    liblber-2.4.so.2 => /lib64/liblber-2.4.so.2 (0x00007fce386de000)
    libsasl2.so.2 => /usr/lib64/libsasl2.so.2 (0x00007fce384c4000)
    libXau.so.6 => /usr/lib64/libXau.so.6 (0x00007fce382c0000)
    libselinux.so.1 => /lib64/libselinux.so.1 (0x00007fce380a1000)

score 1 · Answer 1 · answered Jun 16 '15 at 20:42

Why are you using LD_PRELOAD specifically?

Normally if you have a Python module or application which links a shared library which isn't in a standard directory on the system library search path you would use LD_LIBRARY_PATH.

Using LD_LIBRARY_PATH will still not help with the way you are doing it as either has to be set in the environment before the application process is started. The SetEnv directory doesn't do that for mod_wsgi.

What you would normally do to get around this problem is to set a different environment variable again, called LD_RUN_PATH, but set it at the time you are compiling the Python module, application or library which requires it.

Thus, when installing the Python module requiring it, do:

LD_RUN_PATH=/opt/gdal-custom/lib pip install somemodule

Passing LD_PRELOAD to apache 2.4 for mod_wsgi

1 Answers1