cluster/dht: Make rebalance throttle option tuned by number

Current rebalance throttle options: lazy/normal/aggressive may not always be
sufficient for the purpose of throttling.  In our recent test, we observed for
certain setups, normal and aggressive modes behaved similarly consuming full
disk bandwidth. So in cases like this admin should be able to  tune it
down(or vice versa) depending on the need.

Along with old throttle configurations, thread counts are tuned based on number.
e.g. gluster v set vol-name cluster-rebal.throttle  5.

Admin can tune up/down between 0 and the number of cores available.

Note: For heterogenous servers, validation will fail on the old server if "number"
is given for throttle configuration.
The message looks something like this:
"volume set: failed: Staging failed on vm2. Error: cluster.rebal-throttle should be {lazy|normal|aggressive}"

Test: Manual test by logging active thread number after reconfiguring throttle option.
testcase: tests/basic/distribute/throttle-rebal.t

> Change-Id: I46e3cde546900307831028b344ecf601fd9b02c3
> BUG: 1438370
> Signed-off-by: Susant Palai <spalai@redhat.com>
> Reviewed-on: https://review.gluster.org/16980
> NetBSD-regression: NetBSD Build System <jenkins@build.gluster.org>
> Smoke: Gluster Build System <jenkins@build.gluster.org>
> CentOS-regression: Gluster Build System <jenkins@build.gluster.org>
> Reviewed-by: Atin Mukherjee <amukherj@redhat.com>
> Reviewed-by: Raghavendra G <rgowdapp@redhat.com>
> Signed-off-by: Susant Palai <spalai@redhat.com>

Change-Id: I46e3cde546900307831028b344ecf601fd9b02c3
BUG: 1473136
Signed-off-by: Susant Palai <spalai@redhat.com>
Reviewed-on: https://review.gluster.org/17835
CentOS-regression: Gluster Build System <jenkins@build.gluster.org>
Smoke: Gluster Build System <jenkins@build.gluster.org>
Reviewed-by: Shyamsundar Ranganathan <srangana@redhat.com>

1 files changed, 28 insertions, 4 deletions

diff --git a/xlators/mgmt/glusterd/src/glusterd-volume-set.c b/xlators/mgmt/glusterd/src/glusterd-volume-set.c
index dac9d4eabfd..6bf07233a70 100644
--- a/xlators/mgmt/glusterd/src/glusterd-volume-set.c
+++ b/xlators/mgmt/glusterd/src/glusterd-volume-set.c
@@ -547,21 +547,45 @@ static int
 validate_defrag_throttle_option (glusterd_volinfo_t *volinfo, dict_t *dict,
                                  char *key, char *value, char **op_errstr)
 {
-        char                 errstr[2048] = "";
-        int                  ret          = 0;
-        xlator_t            *this         = NULL;
+        char                 errstr[2048]       = "";
+        int                  ret                = 0;
+        xlator_t            *this               = NULL;
+        int                  thread_count       = 0;
+        long int             cores_available    = 0;
 
         this = THIS;
         GF_ASSERT (this);
 
+        cores_available = sysconf(_SC_NPROCESSORS_ONLN);
+
+        /* Throttle option should be one of lazy|normal|aggressive or a number
+         * configured by user max up to the number of cores in the machine */
+
         if (!strcasecmp (value, "lazy") ||
             !strcasecmp (value, "normal") ||
             !strcasecmp (value, "aggressive")) {
                 ret = 0;
+        } else if ((gf_string2int (value, &thread_count) == 0)) {
+                if ((thread_count > 0) && (thread_count <= cores_available)) {
+                        ret = 0;
+                } else {
+                        ret = -1;
+                        snprintf (errstr, sizeof (errstr), "%s should be within"
+                                  " range of 0 and maximum number of cores "
+                                  "available (cores available - %ld)", key,
+                                  cores_available);
+
+                        gf_msg (this->name, GF_LOG_ERROR, EINVAL,
+                                GD_MSG_INVALID_ENTRY, "%s", errstr);
+
+                        *op_errstr = gf_strdup (errstr);
+                }
         } else {
                 ret = -1;
                 snprintf (errstr, sizeof (errstr), "%s should be "
-                          "{lazy|normal|aggressive}", key);
+                          "{lazy|normal|aggressive} or a number upto number of"
+                          " cores available (cores availble - %ld)", key,
+                          cores_available);
                 gf_msg (this->name, GF_LOG_ERROR, EINVAL,
                         GD_MSG_INVALID_ENTRY, "%s", errstr);
                 *op_errstr = gf_strdup (errstr);