A requirement came to me that we need to enable timeout in php-curl with timeout values being in millisecond. We cant even wait for a second to curl to terminate. Php uses native curl in unix systems. The curl supports this feature in version>7.19. For our OS the curl version is 7.15. Ofcourse we can install 7.19 using rpm or source
But php had a wrapper module curl.so, so all php-curl method call will go to curl.so which inturn will call native curl. So curl.so is not aware of the timeout_ms in feature and started throwing php errors.
A hack would be to replace curl.so with the one which supports timeout_ms from other version of OS.
But nobody is interested in this change because if something crashes in production, it would be huge effort and loss.
I downloaded the Source RPMS(RPM are binary and Source RPMS will have the source code and SPEC file). The SPEC file will take care of configure, make and install part (which we have to do manually if we install from source). I could not find any difference in any file of php SRPM between our OS and newer version of the same distro.
Since we need this change within week, we decided to upgrade our OS. Upgrading OS can break something which wont be in our sight. We started a sequence of tests in the newer version of OS and came up with a schedule and approval from concerned leads.
Then I was asked why cant we recompile php by my manager during an informal meet. I was pretty much sure recompiling php wont work because both SRPMS dont differ by any means(stupidity 1).
There is a file interface.c in php source code which adds features based on the curl version.
#if LIBCURL_VERSION_NUM > 0x071002
Next my assumption was if I have correct curl(dynamic libraries) before installing php, php-curl would detect the feature automatically(stupidity 2).
This didnt work, php threw an error dependency module libcurl.so.3 not found despite libcurl.so.4 module present(new version).
Lets understand the process of C compilation before understanding this issue
C preprocesses all source file, header files and compiles them and links static libraries to form binary. Hereafter we dont need the header files to run binaries.
The same thing happens once we build rpm, we need curl-devel(similar to curl.h files)to build rpm and we dont need them once binary is created. They are called build dependency.
This php module is built with curl-devel version<7.19. So it requires dynamic library libcurl.so.3 while running. I have to just rebuild php with the latest version of curl-devel to detect libcurl.so.4.
We were almost prepared for a big change in our infrastructure without looking for an available easier option.