login: one command for logging-in to all gateways of a target

Currently from the initiator side we need to login to mpath no. of
nodes individually for establishing connect with all multipathed
block devices from the client side, thus we need to execute mpath no.
of login commands (i.e. login to each server)

This can be minimized to single login command per target by configuring
all gateways for a particular target in all gateways.

Currently,
$ gluster-block create VOL/BLOCK ha 3 HOSTx,HOSTy,HOSTz 10GiB
Creates only one TPG i.e tpg1 (Read as Target Portal Group with Tag 1)
on each node/server, with one portal listening on respective IP. All
the gateways/nodes emulate same backend as target LUN with same WWN
(for multipath representation)

So at client side. we need to execute 3 commands to login all gateways
$ iscsiadm -m discovery -t st -p HOSTy -l
$ iscsiadm -m discovery -t st -p HOSTz -l
$ iscsiadm -m discovery -t st -p HOSTx -l

In the above case, user may login in any fashion, which is out of our
control. Since we have failover multipath configuration, at a given
time only one gateway can TX RX the data. so predicting active
path/connection is not possible.

With this patch,
$ gluster-block create VOL/BLOCK ha 3 HOSTx,HOSTy,HOSTz 10GiB
Creates 3 TPG's, tpg1(portal HOSTx), tpg2(portal HOSTy) and
tpg3(portal HOSTz) on all the three gateways/nodes (IN same order).

Basically, each gateway is define to every other gateway - but the
other (other than local) gateway entries are in a disabled state.
When the client starts the login sequence it issues the RPTG to the
one nodes, but now that node can respond with portal IP's for all of
the gateways.

e.g.
   GW1                GW2                 GW3
 - tpg1/enabled     - tpg1/disabled     - tpg1/disabled
 - tpg2/disabled    - tpg2/enabled      - tpg2/disabled
 - tpg3/disabled    - tpg3/disabled     - tpg3/enabled

Advantage,

* Only one login command is needed, unlike 3 login's before,
  $ iscsiadm -m discovery -t st -p ANYONEHOST -l

* Always tpg1 will be tried for making an active path/connection,
  hence we can predict that the first host in the list {HOSTx,HOSTy,HOSTz}
  will be tried for active connection. Hence we can be able to better
  manage load on each nodes, by selectively supplying Hosts in the list.

Change-Id: I70f73b1d46812cb1bd8dc80f771ec20b0f0415bf
Fixes: #9
Signed-off-by: Prasanna Kumar Kalever <prasanna.kalever@redhat.com>

1 files changed, 28 insertions, 35 deletions

diff --git a/cli/gluster-block.c b/cli/gluster-block.c
index a980110..afa1262 100644
--- a/cli/gluster-block.c
+++ b/cli/gluster-block.c
@@ -34,15 +34,26 @@ const char *argp_program_version = ""                                 \
   "or later), or the GNU General Public License, version 2 (GPLv2),\n"\
   "in all cases as published by the Free Software Foundation.";
 
-#define GB_CREATE_HELP_STR "gluster-block create <volname/blockname> "\
-                           "[ha <count>] [auth enable|disable] "\
-                           "<HOST1[,HOST2,...]> <size> [--json*]"
 
-#define GB_DELETE_HELP_STR "gluster-block delete <volname/blockname> [--json*]"
-#define GB_MODIFY_HELP_STR "gluster-block modify <volname/blockname> "\
-                           "<auth enable|disable> [--json*]"
-#define GB_INFO_HELP_STR  "gluster-block info <volname/blockname> [--json*]"
-#define GB_LIST_HELP_STR  "gluster-block list <volname> [--json*]"
+# define  GB_CREATE_HELP_STR  "gluster-block create <volname/blockname> "\
+                                "[ha <count>] [auth enable|disable] "\
+                                "<HOST1[,HOST2,...]> <size> [--json*]"
+
+# define  GB_DELETE_HELP_STR  "gluster-block delete <volname/blockname> [--json*]"
+# define  GB_MODIFY_HELP_STR  "gluster-block modify <volname/blockname> "\
+                               "<auth enable|disable> [--json*]"
+# define  GB_INFO_HELP_STR    "gluster-block info <volname/blockname> [--json*]"
+# define  GB_LIST_HELP_STR    "gluster-block list <volname> [--json*]"
+
+
+# define  GB_ARGCHECK_OR_RETURN(argcount, count, cmd, helpstr)        \
+          do {                                                        \
+            if (argcount != count) {                                  \
+              MSG("Inadequate arguments for %s:\n%s\n", cmd, helpstr);\
+              return -1;                                              \
+            }                                                         \
+          } while(0)
+
 
 static int
 glusterBlockCliRPC_1(void *cobj, clioperations opt, char **out)
@@ -273,12 +284,10 @@ glusterBlockModify(int argcount, char **options, int json)
   int ret = -1;
   char *out = NULL;
 
+
+  GB_ARGCHECK_OR_RETURN(argcount, 5, "modify", GB_MODIFY_HELP_STR);
+
   mobj.json_resp = json;
-  if (argcount != 5) {
-    MSG("%s\n", "Insufficient arguments for modify:");
-    MSG("%s\n", GB_MODIFY_HELP_STR);
-    return -1;
-  }
 
   if (glusterBlockParseVolumeBlock (options[optind++], mobj.volume,
                                     mobj.block_name, GB_MODIFY_HELP_STR,
@@ -330,12 +339,11 @@ glusterBlockCreate(int argcount, char **options, int json)
   blockCreateCli cobj = {0, };
 
 
-  cobj.json_resp = json;
   if (argcount <= optind) {
-    MSG("%s\n", "Insufficient arguments for create:");
-    MSG("%s\n", GB_CREATE_HELP_STR);
+    MSG("Inadequate arguments for create:\n%s\n", GB_CREATE_HELP_STR);
     return -1;
   }
+  cobj.json_resp = json;
 
   /* default mpath */
   cobj.mpath = 1;
@@ -375,8 +383,7 @@ glusterBlockCreate(int argcount, char **options, int json)
   }
 
   if (argcount - optind < 2) {  /* left with servers and size so 2 */
-    MSG("%s\n", "Insufficient arguments for create");
-    MSG("%s\n", GB_CREATE_HELP_STR);
+    MSG("Inadequate arguments for create:\n%s\n", GB_CREATE_HELP_STR);
     LOG("cli", GB_LOG_ERROR,
         "failed creating block %s on volume %s with hosts %s",
         cobj.block_name, cobj.volume, cobj.block_hosts);
@@ -428,12 +435,8 @@ glusterBlockList(int argcount, char **options, int json)
   int ret = -1;
 
 
+  GB_ARGCHECK_OR_RETURN(argcount, 3, "list", GB_LIST_HELP_STR);
   cobj.json_resp = json;
-  if (argcount != 3) {
-    MSG("%s\n", "Insufficient arguments for list:");
-    MSG("%s\n", GB_LIST_HELP_STR);
-    return -1;
-  }
 
   strcpy(cobj.volume, options[2]);
 
@@ -461,13 +464,8 @@ glusterBlockDelete(int argcount, char **options, int json)
   int ret = -1;
 
 
+  GB_ARGCHECK_OR_RETURN(argcount, 3, "delete", GB_DELETE_HELP_STR);
   cobj.json_resp = json;
-  if (argcount != 3) {
-    MSG("%s\n", "Insufficient arguments for delete:");
-    MSG("%s\n", GB_DELETE_HELP_STR);
-    return -1;
-  }
-
 
   if (glusterBlockParseVolumeBlock (options[2], cobj.volume,
                                     cobj.block_name, GB_DELETE_HELP_STR,
@@ -500,13 +498,8 @@ glusterBlockInfo(int argcount, char **options, int json)
   int ret = -1;
 
 
+  GB_ARGCHECK_OR_RETURN(argcount, 3, "info", GB_INFO_HELP_STR);
   cobj.json_resp = json;
-  if (argcount != 3) {
-    MSG("%s\n", "Insufficient arguments for info:");
-    MSG("%s\n", GB_INFO_HELP_STR);
-    return -1;
-  }
-
 
   if (glusterBlockParseVolumeBlock (options[2], cobj.volume,
                                     cobj.block_name, GB_INFO_HELP_STR,