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What is mod_glusterfs?
======================
* mod_glusterfs is a module for apache written for efficient serving of files from glusterfs.
mod_glusterfs interfaces with glusterfs using apis provided by libglusterfsclient.
* this README speaks about installation of apache-1.3.x, where x is any minor version.
Prerequisites for mod_glusterfs
===============================
Though mod_glusterfs has been written as a module, with an intent of making no changes to the way apache has
been built, currently following points have to be taken care of:
* module "so" has to be enabled, for apache to support modules.
* since glusterfs is compiled with _FILE_OFFSET_BITS=64 and __USE_FILE_OFFSET64 flags, mod_glusterfs and apache
in turn have to be compiled with the above two flags.
$ tar xzvf apache-1.3.9.tar.gz
$ cd apache-1.3.9/
$ # add -D_FILE_OFFSET_BITS=64 -D__USE_FILE_OFFSET64 to EXTRA_CFLAGS in src/Configuration.
$ ./configure --prefix=/usr --enable-module=so
$ cd src
$ ./Configure
$ cd ../
$ make install
$ httpd -l | grep -i mod_so
mod_so.c
* if multiple apache installations are present, make sure to pass --with-apxs=/path/to/apxs/of/proper/version to configure script while building glusterfs.
Build/Install mod_glusterfs
===========================
* mod_glusterfs is provided with glusterfs--mainline--3.0 and all releases from the same branch.
* building glusterfs also builds mod_glusterfs. But 'make install' of glusterfs installs mod_glusterfs.so to
glusterfs install directory instead of the apache modules directory.
* 'make install' of glusterfs will print a message similar to the one given below, which is self explanatory.
Make sure to use apxs of proper apache version in case of multiple apache installations. This will copy
mod_glusterfs.so to modules directory of proper apache version and modify the appropriate httpd.conf to enable
mod_glusterfs.
**********************************************************************************************
* TO INSTALL MODGLUSTERFS, PLEASE USE,
* apxs -n mod_glusterfs -ia /usr/lib/glusterfs/1.4.0pre2/apache-1.3/mod_glusterfs.so
**********************************************************************************************
Configuration
=============
* Following configuration has to be added to httpd.conf.
<Location "/glusterfs">
GlusterfsLogfile "/var/log/glusterfs/glusterfs.log"
GlusterfsLoglevel "warning"
GlusterfsVolumeSpecfile "/etc/glusterfs/glusterfs-client.spec"
GlusterfsCacheTimeout "600"
GlusterfsXattrFileSize "65536"
SetHandler "glusterfs-handler"
</Location>
* GlusterfsVolumeSpecfile (COMPULSORY)
Path to the the glusterfs volume specification file.
* GlusterfsLogfile (COMPULSORY)
Path to the glusterfs logfile.
* GlusterfsLoglevel (OPTIONAL, default = warning)
Severity of messages that are to be logged. Allowed values are critical, error, warning, debug, none
in the decreasing order of severity.
* GlusterfsCacheTimeOut (OPTIONAL, default = 0)
Timeout values for glusterfs stat and lookup cache.
* GlusterfsXattrFileSize (OPTIONAL, default = 0)
Files with sizes upto and including this value are fetched through the extended attribute interface of
glusterfs rather than the usual open-read-close set of operations. For files of small sizes, it is recommended
to use extended attribute interface.
* With the above configuration all the requests to httpd of the form www.example.org/glusterfs/path/to/file are
served from glusterfs.
Miscellaneous points
====================
* httpd by default runs with username "nobody" and group "nogroup". Permissions of logfile and specfile have to
be set suitably.
* Since mod_glusterfs runs with permissions of nobody.nogroup, glusterfs has to use only login based
authentication. See docs/authentication.txt for more details.
* To copy the data served by httpd into glusterfs mountpoint, glusterfs can be started with the
volume-specification file provided to mod_glusterfs. Any tool like cp can then be used.
* To run in gdb, apache has to be compiled with -lpthread, since libglusterfsclient is multithreaded.
If not on Linux gdb runs into errors like:
"Error while reading shared library symbols:
Cannot find new threads: generic error"
* when used with ib-verbs transport, ib_verbs initialization fails.
reason for this is that apache runs as non-privileged user and the amount of memory that can be
locked by default is not sufficient for ib-verbs. to fix this, as root run,
# ulimit -l unlimited
and then start apache.
TODO
====
* directory listing for the directories accessed through mod_glusterfs.
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