From 1e62ff42dfcf84ded563f710cb8da92fa0f41936 Mon Sep 17 00:00:00 2001 From: Ram Raja Date: Tue, 30 Apr 2013 00:38:04 +0530 Subject: glupy: Importing Jeff's glupy project into glusterfs Change-Id: I3891ef6eaf6ede7c8cbedc3298ce2501a69b2b05 BUG: 961856 Original-author: Jeff Darcy Signed-off-by: Ram Raja Reviewed-on: http://review.gluster.org/4906 Reviewed-by: Justin Clift Tested-by: Justin Clift --- xlators/features/glupy/doc/README.md | 44 ++++++++++++++++++++++++++++++++++++ 1 file changed, 44 insertions(+) create mode 100644 xlators/features/glupy/doc/README.md (limited to 'xlators/features/glupy/doc') diff --git a/xlators/features/glupy/doc/README.md b/xlators/features/glupy/doc/README.md new file mode 100644 index 000000000..2d7b30ef6 --- /dev/null +++ b/xlators/features/glupy/doc/README.md @@ -0,0 +1,44 @@ +This is just the very start for a GlusterFS[1] meta-translator that will +allow translator code to be written in Python. It's based on the standard +Python embedding (not extending) techniques, plus a dash of the ctypes module. +The interface is a pretty minimal adaptation of the dispatches and callbacks +from the C API[2] to Python, as follows: + +* Dispatch functions and callbacks must be defined on an "xlator" class + derived from gluster.Translator so that they'll be auto-registered with + the C translator during initialization. + +* For each dispatch or callback function you want to intercept, you define a + Python function using the xxx\_fop\_t or xxx\_cbk\_t decorator. + +* The arguments for each operation are different, so you'll need to refer to + the C API. GlusterFS-specific types are used (though only loc\_t is fully + defined so far) and type correctness is enforced by ctypes. + +* If you do intercept a dispatch function, it is your responsibility to call + xxx\_wind (like STACK\_WIND in the C API but operation-specific) to pass + the request to the next translator. If you do not intercept a function, it + will default the same way as for C (pass through to the same operation with + the same arguments on the first child translator). + +* If you intercept a callback function, it is your responsibility to call + xxx\_unwind (like STACK\_UNWIND\_STRICT in the C API) to pass the request back + to the caller. + +So far only the lookup and create operations are handled this way, to support +the "negative lookup" example. Now that the basic infrastructure is in place, +adding more functions should be very quick, though with that much boilerplate I +might pause to write a code generator. I also plan to add structure +definitions and interfaces for some of the utility functions in libglusterfs +(especially those having to do with inode and fd context) in the fairly near +future. Note that you can also use ctypes to get at anything not explicitly +exposed to Python already. + +_If you're coming here because of the Linux Journal article, please note that +the code has evolved since that was written. The version that matches the +article is here:_ + +https://github.com/jdarcy/glupy/tree/4bbae91ba459ea46ef32f2966562492e4ca9187a + +[1] http://www.gluster.org +[2] http://hekafs.org/dist/xlator_api_2.html -- cgit