api: add glfs_get_volfile

From the API-header description:

> Sometimes it's useful e.g. for scripts to see the volfile, so that
> they can parse it and find subvolumes to do things like split-brain
> resolution or custom layouts.  The API here was specifically intended
> to make access e.g. from Python as simple as possible.
>
> Note that the volume must be started (not necessarily mounted) for
> this to work.

Change-Id: If3f55ee9611cdf4b77aa53659f0af0d21957817d
Signed-off-by: Jeff Darcy <jdarcy@redhat.com>
Reviewed-on: http://review.gluster.org/7183
Reviewed-by: Anand Avati <avati@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>

1 files changed, 43 insertions, 0 deletions

diff --git a/api/examples/getvolfile.py b/api/examples/getvolfile.py
new file mode 100755
index 00000000000..82d9db05510
--- /dev/null
+++ b/api/examples/getvolfile.py
@@ -0,0 +1,43 @@
+#!/usr/bin/python
+
+import ctypes
+import ctypes.util
+
+api = ctypes.CDLL(ctypes.util.find_library("gfapi"))
+api.glfs_get_volfile.argtypes = [ctypes.c_void_p,
+							     ctypes.c_void_p,
+								 ctypes.c_ulong]
+api.glfs_get_volfile.restype = ctypes.c_long;
+
+def get_volfile (host, volume):
+	# This is set to a large value to exercise the "buffer not big enough"
+	# path.  More realistically, you'd just start with a huge buffer.
+	BUF_LEN = 0
+	fs = api.glfs_new(volume)
+	#api.glfs_set_logging(fs,"/dev/stderr",7)
+	api.glfs_set_volfile_server(fs,"tcp",host,24007)
+	api.glfs_init(fs)
+	vbuf = ctypes.create_string_buffer(BUF_LEN)
+	vlen = api.glfs_get_volfile(fs,vbuf,BUF_LEN)
+	if vlen < 0:
+		vlen = BUF_LEN - vlen
+		vbuf = ctypes.create_string_buffer(vlen)
+		vlen = api.glfs_get_volfile(fs,vbuf,vlen)
+	api.glfs_fini(fs)
+	if vlen <= 0:
+		return vlen
+	return vbuf.value[:vlen]
+
+if __name__ == "__main__":
+	import sys
+
+	try:
+		res = apply(get_volfile,sys.argv[1:3])
+	except:
+		print "fetching volfile failed (volume not started?)"
+
+	try:
+		for line in res.split('\n'):
+			print line
+	except:
+		print "bad return value %s" % res