cluster/dht: Add tier translator.

The tier translator shares most of DHT's code. It differs in how
subvolumes are chosen for I/Os, and how file migration (cache promotion
and demotion) is managed. That different functionality is split to either
DHT or tier logic according to the "tier_methods" structure.

A cache promotion and demotion thread is created in a manner
similar to the rebalance daemon. The thread operates a timing
wheel which periodically checks for promotion and demotion candidates
(files). Candidates are queued and then migrated. Candidates must exist on
the same node as the daemon and meet other critera per caching policies.

This patch has two authors (Dan Lambright and Joseph Fernandes). Dan
did the DHT changes and Joe wrote the cache policies. The fix depends on
DHT readidr changes and the database library which have been submitted
separately.  Header files in libglusterfs/src/gfdb should be reviewed in
patch 9683.

For more background and design see the feature page [1].

[1]
http://www.gluster.org/community/documentation/index.php/Features/data-classification

Change-Id: Icc26c517ccecf5c42aef039f5b9c6f7afe83e46c
BUG: 1194753
Signed-off-by: Dan Lambright <dlambrig@redhat.com>
Reviewed-on: http://review.gluster.org/9724
Reviewed-by: Vijay Bellur <vbellur@redhat.com>
Tested-by: Vijay Bellur <vbellur@redhat.com>

1 files changed, 31 insertions, 0 deletions

diff --git a/xlators/cluster/dht/src/dht-shared.c b/xlators/cluster/dht/src/dht-shared.c
index 860f3e716f0..1e666bd8140 100644
--- a/xlators/cluster/dht/src/dht-shared.c
+++ b/xlators/cluster/dht/src/dht-shared.c
@@ -29,6 +29,8 @@
 */
 struct volume_options options[];
 
+extern dht_methods_t dht_methods;
+
 void
 dht_layout_dump (dht_layout_t  *layout, const char *prefix)
 {
@@ -701,6 +703,8 @@ dht_init (xlator_t *this)
         if (dht_set_subvol_range(this))
                 goto err;
 
+        conf->methods = &dht_methods;
+
         return 0;
 
 err:
@@ -847,6 +851,33 @@ struct volume_options options[] = {
           .type = GF_OPTION_TYPE_XLATOR
         },
 
+        /* tier options */
+        { .key  = {"tier-promote-frequency"},
+          .type = GF_OPTION_TYPE_INT,
+          .default_value = "120",
+          .description = "Frequency to promote files to fast tier"
+        },
+
+        { .key  = {"tier-demote-frequency"},
+          .type = GF_OPTION_TYPE_INT,
+          .default_value = "120",
+          .description = "Frequency to demote files to slow tier"
+        },
+
+        { .key  = {"write-freq-thresold"},
+          .type = GF_OPTION_TYPE_INT,
+          .default_value = "0",
+          .description = "Defines the write fequency "
+                        "that would be considered hot"
+        },
+
+        { .key  = {"read-freq-thresold"},
+          .type = GF_OPTION_TYPE_INT,
+          .default_value = "0",
+          .description = "Defines the read fequency "
+                        "that would be considered hot"
+        },
+
         /* switch option */
         { .key  = {"pattern.switch.case"},
           .type = GF_OPTION_TYPE_ANY