Metricbeat: Add memcached used bytes metrics

CHANGELOG.asciidoc

@@ -325,6 +325,7 @@ https://github.com/elastic/beats/compare/v6.2.3...master[Check the HEAD diff]
 - Release prometheus collector metricset as GA. {pull}7660[7660]
 - Add Elasticsearch `cluster_stats` metricset. {pull}7638[7638]
 - Added `basepath` setting for HTTP-based metricsets {pull}7700[7700]
+- Add metrics about cache size to memcached module {pull}7740[7740]
 
 *Packetbeat*
 

metricbeat/docs/fields.asciidoc

@@ -9684,6 +9684,26 @@ type: long
 Number of objects removed from the cache to free up memory for new items because Memcached reached it's maximum memory setting (limit_maxbytes).
 
 
+--
+
+*`memcached.stats.bytes.current`*::
++
+--
+type: long
+
+Number of bytes currently used for caching items.
+
+
+--
+
+*`memcached.stats.bytes.limit`*::
++
+--
+type: long
+
+Number of bytes this server is allowed to use for storage.
+
+
 --
 
 [[exported-fields-mongodb]]

metricbeat/module/memcached/stats/_meta/data.json

@@ -6,6 +6,10 @@
     },
     "memcached": {
         "stats": {
+            "bytes": {
+                "current": 0,
+                "limit": 67108864
+            },
             "cmd": {
                 "get": 0,
                 "set": 0
@@ -42,4 +46,4 @@
         "name": "stats",
         "rtt": 115
     }
-}
+}

metricbeat/module/memcached/stats/_meta/fields.yml

@@ -83,3 +83,15 @@
       description: >
         Number of objects removed from the cache to free up memory for new items
         because Memcached reached it's maximum memory setting (limit_maxbytes).
+
+    - name: bytes.current
+      type: long
+      formate: bytes
+      description: >
+        Number of bytes currently used for caching items.
+
+    - name: bytes.limit
+      type: long
+      formate: bytes
+      description: >
+        Number of bytes this server is allowed to use for storage.

metricbeat/module/memcached/stats/data.go

@@ -52,5 +52,9 @@ var (
 			"total":   c.Int("total_items"),
 		},
 		"evictions": c.Int("evictions"),
+		"bytes": s.Object{
+			"current": c.Int("bytes"),
+			"limit":   c.Int("limit_maxbytes"),
+		},
 	}
 )