Add halo-min-samples option, better swap logic, edge case fixes

Summary:
- Changes halo-decision to be based on the lowest halo value observed
- Adds halo-min-sample option to wait until N latency samples have been
  gathered prior to activating halos.
- Fixed 3 edge cases where halo's weren't being correctly
  config'd, or not configured as quickly as is possible.  Namely:
  1. Don't mark a child down if there's no better alternative (and you'd
  no longer satisfy min/max replicas); fixes unneccessary flapping.
  2. If a child goes down and this causes us to fall below max_replicas,
  swap in a warm child immediately if it is within our halo latency
  (don't wait around for the next "ping"); swaps in a new child
  immediately helping with resiliency.
  3. If the child latency is within the halo, and it's currently marked
  up, mark it down if it's the highest latency child and the number of
  children is > max_replicas; this will allow us to support the
  SHD use-case where we can "beam" a single copy to a geo and have it
  replicate within the geo after that.
- More commenting

Test Plan:
- Run halo prove tests
- Pointed compiled code at gfsglobal.prn2, tested out an NFS daemon and
  FUSE mounts to ensure they worked as expected on a large scale
  cluster.

Reviewers: dph, jackl, cjh, mmckeen

Reviewed By: mmckeen

FB-commit-id: 7e2e8ae6b8ec62a5e0b31c9fd6100c81795b3424

Change-Id: Iba2b2f1bc848b4546cb96117ff1895f83953a4f8
Signed-off-by: Kevin Vigor <kvigor@fb.com>
Reviewed-on: http://review.gluster.org/16304
CentOS-regression: Gluster Build System <jenkins@build.gluster.org>
NetBSD-regression: NetBSD Build System <jenkins@build.gluster.org>
Smoke: Gluster Build System <jenkins@build.gluster.org>
Reviewed-by: Shreyas Siravara <sshreyas@fb.com>

5 files changed, 136 insertions, 44 deletions

diff --git a/xlators/cluster/afr/src/afr-common.c b/xlators/cluster/afr/src/afr-common.c
index 6973433a03e..8e46117b025 100644
--- a/xlators/cluster/afr/src/afr-common.c
+++ b/xlators/cluster/afr/src/afr-common.c
@@ -43,6 +43,9 @@
 #include "afr-self-heald.h"
 #include "afr-messages.h"
 
+#define CHILD_UP_STR "UP"
+#define CHILD_DOWN_STR "DOWN"
+
 call_frame_t *
 afr_copy_frame (call_frame_t *base)
 {
@@ -4250,48 +4253,76 @@ find_worst_up_child (xlator_t *this)
         return worst_child;
 }
 
-void
+static void
 _afr_handle_ping_event (xlator_t *this, xlator_t *child_xlator,
-                const int idx, int64_t halo_max_latency_msec, int32_t *event,
-                int64_t *child_latency_msec)
+                const int idx, const int64_t halo_max_latency_msec,
+                int32_t *event, int64_t *child_latency_msec,
+                gf_boolean_t child_halo_enabled)
 {
         afr_private_t   *priv               = NULL;
         int             i                   = -1;
         int             up_children         = 0;
+        int             best_down_child     = 0;
+        uint64_t        latency_samples     = 0;
+        char            *child_state_str    = NULL;
 
         priv = this->private;
 
-        *child_latency_msec = child_xlator->client_latency.mean / 1000.0;
+        /* Base it off the _minimum_ latency we've ever seen */
+        *child_latency_msec = child_xlator->client_latency.min / 1000.0;
+        latency_samples = child_xlator->client_latency.count;
         priv->child_latency[idx] = *child_latency_msec;
 
-        for (i = 0; i < priv->child_count; i++)
-                if (priv->child_up[i] == 1)
+        for (i = 0; i < priv->child_count; i++) {
+                if (priv->child_up[i] == 1) {
                         up_children++;
+                        child_state_str = CHILD_UP_STR;
+                } else {
+                    child_state_str = CHILD_DOWN_STR;
+                }
+                gf_log (child_xlator->name, GF_LOG_DEBUG,
+                        "Child %d halo state: %s (%"PRIi64"ms)",
+                        i, child_state_str, priv->child_latency[i]);
+        }
 
-        if (priv->halo_enabled &&
+        /* Don't do anything until you have some minimum numbner of
+         * latency samples */
+        if (priv->halo_enabled == _gf_true && child_halo_enabled == _gf_false) {
+                gf_log (child_xlator->name, GF_LOG_INFO, "In-sufficient "
+                        " number of latency samples (%" PRIu64
+                        " < %d), halo in-active.",
+                        latency_samples, priv->halo_min_samples);
+        }
+
+        /*
+         * Case 1: This child's latency exceeds the maximum allowable
+         * for this halo.
+         */
+        if (child_halo_enabled &&
             *child_latency_msec > halo_max_latency_msec &&
             priv->child_up[idx] == 1 &&
             up_children > priv->halo_min_replicas) {
-                if ((up_children - 1) <
-                    priv->halo_min_replicas &&
-                    priv->halo_failover_enabled) {
+                if (find_worst_up_child (this) == idx) {
                         gf_log (child_xlator->name, GF_LOG_INFO,
-                               "Overriding halo threshold, "
-                               "min replicas: %d",
-                               priv->halo_min_replicas);
-                } else {
-                        gf_log (child_xlator->name, GF_LOG_INFO,
-                                "Child latency (%ld ms) "
-                                "exceeds halo threshold (%ld), "
-                                "marking child down.",
-                                *child_latency_msec,
-                                halo_max_latency_msec);
+                                "Child latency (%"PRIi64"ms) "
+                                 "exceeds halo threshold (%"PRIi64"), "
+                                 "marking child down, "
+                                 "min_replicas (%d) still "
+                                 "satisfied.",
+                                 *child_latency_msec,
+                                 halo_max_latency_msec,
+                                 priv->halo_min_replicas);
                         *event = GF_EVENT_CHILD_DOWN;
                 }
-        } else if ((priv->halo_enabled == _gf_false ||
-                    *child_latency_msec < halo_max_latency_msec) &&
+        /*
+         * Case 2: Child latency is within halo and currently marked down,
+         * mark it up.
+         */
+        } else if ((child_halo_enabled == _gf_false ||
+                    *child_latency_msec <= halo_max_latency_msec) &&
                    priv->child_up[idx] == 0) {
-                if (up_children < priv->halo_max_replicas) {
+                if (child_halo_enabled == _gf_false ||
+                        up_children < priv->halo_max_replicas) {
                         gf_log (child_xlator->name, GF_LOG_INFO,
                                 "Child latency (%ld ms) "
                                 "below halo threshold (%ld) or halo is "
@@ -4305,13 +4336,35 @@ _afr_handle_ping_event (xlator_t *this, xlator_t *child_xlator,
                             "max replicas (%d) reached.", idx,
                             priv->halo_max_replicas);
                 }
+        /*
+         * Case 3: Child latency is within halo,and currently marked up,
+         * mark it down if it's the highest latency child and the
+         * number of up children is greater than halo_max_replicas.
+         */
+        } else if ((child_halo_enabled == _gf_true &&
+                        *child_latency_msec <= halo_max_latency_msec) &&
+                        priv->child_up[idx] == 1) {
+                if (find_worst_up_child (this) == idx &&
+                                up_children > priv->halo_max_replicas &&
+                                !priv->shd.iamshd) {
+                        gf_log (child_xlator->name, GF_LOG_INFO,
+                                "Child latency (%"PRIi64"ms) "
+                                "exceeds halo threshold (%"PRIi64"), "
+                                "but halo_max_replicas (%d) exceeded, "
+                                "marking child down.",
+                                *child_latency_msec,
+                                halo_max_latency_msec,
+                                priv->halo_max_replicas);
+                        *event = GF_EVENT_CHILD_DOWN;
+                }
         }
 }
 
 void
 _afr_handle_child_up_event (xlator_t *this, xlator_t *child_xlator,
                 const int idx, int64_t halo_max_latency_msec,
-                int32_t *event, int32_t *call_psh, int32_t *up_child)
+                int32_t *event, int32_t *call_psh, int32_t *up_child,
+                gf_boolean_t child_halo_enabled)
 {
         afr_private_t   *priv               = NULL;
         int             i                   = -1;
@@ -4321,7 +4374,7 @@ _afr_handle_child_up_event (xlator_t *this, xlator_t *child_xlator,
 
         priv = this->private;
 
-        /*
+       /*
          * This only really counts if the child was never up
          * (value = -1) or had been down (value = 0).  See
          * comment at GF_EVENT_CHILD_DOWN for a more detailed
@@ -4350,8 +4403,8 @@ _afr_handle_child_up_event (xlator_t *this, xlator_t *child_xlator,
          * halo_min_replicas even though it's latency exceeds
          * halo_max_latency_msec.
          */
-        if (priv->halo_enabled == _gf_true &&
-                        up_children > priv->halo_min_replicas) {
+        if (child_halo_enabled == _gf_true &&
+            up_children > priv->halo_min_replicas) {
                 worst_up_child = find_worst_up_child (this);
                 if (worst_up_child >= 0 &&
                     priv->child_latency[worst_up_child] >
@@ -4372,8 +4425,8 @@ _afr_handle_child_up_event (xlator_t *this, xlator_t *child_xlator,
                         goto out;
                 }
         }
-        if (priv->halo_enabled == _gf_true &&
-                        up_children > priv->halo_max_replicas &&
+        if (child_halo_enabled == _gf_true &&
+            up_children > priv->halo_max_replicas &&
             !priv->shd.iamshd) {
                 if (was_down == _gf_true)
                         priv->event_generation--;
@@ -4383,7 +4436,6 @@ _afr_handle_child_up_event (xlator_t *this, xlator_t *child_xlator,
                         worst_up_child = idx;
                 }
                 priv->child_up[worst_up_child] = 0;
-                up_children--;
                 gf_log (this->name, GF_LOG_INFO,
                         "Marking child %d down, "
                         "up_children (%d) > "
@@ -4391,6 +4443,7 @@ _afr_handle_child_up_event (xlator_t *this, xlator_t *child_xlator,
                         worst_up_child,
                         up_children,
                         priv->halo_max_replicas);
+                up_children--;
                 goto out;
         }
 out:
@@ -4408,14 +4461,17 @@ out:
 
 void
 _afr_handle_child_down_event (xlator_t *this, xlator_t *child_xlator,
-                int idx, int64_t child_latency_msec, int32_t *event,
-                int32_t *call_psh, int32_t *up_child)
+                int idx, int64_t child_latency_msec,
+                int64_t halo_max_latency_msec, int32_t *event,
+                int32_t *call_psh, int32_t *up_child,
+                gf_boolean_t child_halo_enabled)
 {
         afr_private_t   *priv               = NULL;
         int             i                   = -1;
         int             up_children         = 0;
         int             down_children       = 0;
         int             best_down_child     = -1;
+        gf_boolean_t    swap_child          = _gf_false;
 
         priv = this->private;
 
@@ -4457,10 +4513,19 @@ _afr_handle_child_down_event (xlator_t *this, xlator_t *child_xlator,
          * as we want it to be up to date if we are going to
          * begin using it synchronously.
          */
-        if (priv->halo_enabled == _gf_true &&
-            up_children < priv->halo_min_replicas &&
-            priv->halo_failover_enabled == _gf_true) {
-                best_down_child = find_best_down_child (this);
+        best_down_child = find_best_down_child (this);
+        if (child_halo_enabled == _gf_true) {
+                if (up_children < priv->halo_min_replicas &&
+                                priv->halo_failover_enabled == _gf_true)
+                        swap_child = _gf_true;
+                else if (up_children < priv->halo_max_replicas &&
+                                priv->child_latency[best_down_child] <=
+                                halo_max_latency_msec &&
+                                priv->halo_failover_enabled == _gf_true)
+                        swap_child = _gf_true;
+        }
+
+        if (swap_child) {
                 if (best_down_child >= 0) {
                         gf_log (this->name, GF_LOG_INFO,
                                 "Swapping out child %d for "
@@ -4524,12 +4589,14 @@ afr_notify (xlator_t *this, int32_t event,
         int             ret                 = -1;
         int             call_psh            = 0;
         int             up_child            = -1;
+        uint64_t        latency_samples     = 0;
         dict_t          *input              = NULL;
         dict_t          *output             = NULL;
         gf_boolean_t    had_quorum          = _gf_false;
         gf_boolean_t    has_quorum          = _gf_false;
         int64_t         halo_max_latency_msec = 0;
         int64_t         child_latency_msec   = -1;
+        gf_boolean_t    child_halo_enabled   = _gf_false;
 
         child_xlator = (xlator_t *)data;
         priv = this->private;
@@ -4544,7 +4611,7 @@ afr_notify (xlator_t *this, int32_t event,
          * O(N^2) overall, but N is small for AFR so it shouldn't be an issue.
          */
         priv->did_discovery = _gf_false;
-
+        latency_samples = child_xlator->client_latency.count;
 
         /* parent xlators dont need to know about every child_up, child_down
          * because of afr ha. If all subvolumes go down, child_down has
@@ -4565,9 +4632,12 @@ afr_notify (xlator_t *this, int32_t event,
         had_quorum = priv->quorum_count && afr_has_quorum (priv->child_up,
                                                            this);
 
-        if (!priv->halo_enabled) {
+        if (!priv->halo_enabled ||
+            latency_samples < priv->halo_min_samples) {
+                child_halo_enabled = _gf_false;
                 halo_max_latency_msec = INT64_MAX;
         } else {
+                child_halo_enabled = _gf_true;
                 halo_max_latency_msec = _afr_get_halo_latency (this);
         }
 
@@ -4578,7 +4648,7 @@ afr_notify (xlator_t *this, int32_t event,
                 {
                         _afr_handle_ping_event (this, child_xlator, idx,
                                 halo_max_latency_msec, &event,
-                                &child_latency_msec);
+                                &child_latency_msec, child_halo_enabled);
                 }
                 UNLOCK (&priv->lock);
         }
@@ -4611,13 +4681,14 @@ afr_notify (xlator_t *this, int32_t event,
                 case GF_EVENT_CHILD_UP:
                         _afr_handle_child_up_event (this, child_xlator,
                                 idx, halo_max_latency_msec, &event, &call_psh,
-                                &up_child);
+                                &up_child, child_halo_enabled);
                         break;
 
                 case GF_EVENT_CHILD_DOWN:
                         _afr_handle_child_down_event (this, child_xlator, idx,
-                                child_latency_msec, &event, &call_psh,
-                                &up_child);
+                                child_latency_msec, halo_max_latency_msec,
+                                &event, &call_psh, &up_child,
+                                child_halo_enabled);
                         break;
 
                 case GF_EVENT_CHILD_CONNECTING:
diff --git a/xlators/cluster/afr/src/afr.c b/xlators/cluster/afr/src/afr.c
index 27309985e82..d4dd8ff8815 100644
--- a/xlators/cluster/afr/src/afr.c
+++ b/xlators/cluster/afr/src/afr.c
@@ -201,6 +201,9 @@ reconfigure (xlator_t *this, dict_t *options)
         GF_OPTION_RECONF ("halo-min-replicas", priv->halo_min_replicas, options,
                               uint32, out);
 
+        GF_OPTION_RECONF ("halo-min-samples", priv->halo_min_samples, options,
+                              uint32, out);
+
         GF_OPTION_RECONF ("read-subvolume", read_subvol, options, xlator, out);
 
         GF_OPTION_RECONF ("read-hash-mode", priv->hash_mode,
@@ -435,6 +438,8 @@ init (xlator_t *this)
                         out);
         GF_OPTION_INIT ("halo-min-replicas", priv->halo_min_replicas, uint32,
                         out);
+        GF_OPTION_INIT ("halo-min-samples", priv->halo_min_samples, uint32,
+                        out);
 
         GF_OPTION_INIT ("halo-nfsd-max-latency",
                         priv->nfsd.halo_max_latency_msec, uint32, out);
@@ -762,8 +767,16 @@ struct volume_options options[] = {
           .default_value = "2",
            .description = "The minimum number of halo replicas, before adding "
                           "out of region replicas."
-         },
-         { .key  = {"heal-wait-queue-length"},
+        },
+        { .key   = {"halo-min-samples"},
+          .type  = GF_OPTION_TYPE_INT,
+          .min   = 1,
+          .max   = 99999,
+          .default_value = "3",
+           .description = "The minimum number of halo latency samples, before "
+                          "we start forming the halos."
+        },
+        { .key  = {"heal-wait-queue-length"},
           .type = GF_OPTION_TYPE_INT,
           .min  = 0,
           .max  = 10000, /*Around 100MB with sizeof(afr_local_t)= 10496 bytes*/
diff --git a/xlators/cluster/afr/src/afr.h b/xlators/cluster/afr/src/afr.h
index eebcc12b1ee..f66cdbbf56a 100644
--- a/xlators/cluster/afr/src/afr.h
+++ b/xlators/cluster/afr/src/afr.h
@@ -153,6 +153,7 @@ typedef struct _afr_private {
         uint32_t               halo_max_latency_msec;
         uint32_t               halo_max_replicas;
         uint32_t               halo_min_replicas;
+        uint32_t               halo_min_samples;
 
         afr_self_heald_t       shd;
         struct afr_nfsd        nfsd;
diff --git a/xlators/mgmt/glusterd/src/glusterd-volume-set.c b/xlators/mgmt/glusterd/src/glusterd-volume-set.c
index ab00914e3e2..f28294301f8 100644
--- a/xlators/mgmt/glusterd/src/glusterd-volume-set.c
+++ b/xlators/mgmt/glusterd/src/glusterd-volume-set.c
@@ -3068,6 +3068,11 @@ struct volopt_map_entry glusterd_volopt_map[] = {
           .op_version = 2,
           .flags      = OPT_FLAG_CLIENT_OPT
         },
+        { .key        = "cluster.halo-min-samples",
+          .voltype    = "cluster/replicate",
+          .op_version = 2,
+          .flags      = OPT_FLAG_CLIENT_OPT
+        },
         { .key         = NULL
         }
 };
diff --git a/xlators/protocol/client/src/client.c b/xlators/protocol/client/src/client.c
index 7bde1c21410..3e18b4870ae 100644
--- a/xlators/protocol/client/src/client.c
+++ b/xlators/protocol/client/src/client.c
@@ -2750,6 +2750,8 @@ init (xlator_t *this)
 
         this->private = conf;
 
+        this->client_latency.min = UINT64_MAX;
+
         /* If it returns -1, then its a failure, if it returns +1 we need
            have to understand that 'this' is subvolume of a xlator which,
            will set the remote host and remote subvolume in a setxattr