internal: move statistics.lua to stats/storage.lua

The commit moves storage-specific statistics into a file with another
name to make clear its purpose.

Part of #69

sharded-queue-scm-1.rockspec

@@ -28,7 +28,7 @@ build = {
             ['sharded_queue.utils'] = 'sharded_queue/utils.lua',
             ['sharded_queue.stash'] = 'sharded_queue/stash.lua',
             ['sharded_queue.state'] = 'sharded_queue/state.lua',
-            ['sharded_queue.statistics'] = 'sharded_queue/statistics.lua',
+            ['sharded_queue.stats.storage'] = 'sharded_queue/stats/storage.lua',
             ['sharded_queue.version'] = 'sharded_queue/version.lua',
         },
     },

sharded_queue/drivers/fifo.lua

@@ -1,10 +1,10 @@
 local state = require('sharded_queue.state')
 local utils = require('sharded_queue.utils')
 local log = require('log') -- luacheck: ignore
-local statistics = require('sharded_queue.statistics')
+local stats = require('sharded_queue.stats.storage')
 
 local function update_stat(tube_name, name)
-    statistics.update(tube_name, name, '+', 1)
+    stats.update(tube_name, name, '+', 1)
 end
 
 local method = {}

sharded_queue/drivers/fifottl.lua

@@ -1,7 +1,7 @@
 local fiber = require('fiber')
 local state = require('sharded_queue.state')
 local utils = require('sharded_queue.utils')
-local statistics = require('sharded_queue.statistics')
+local stats = require('sharded_queue.stats.storage')
 local time  = require('sharded_queue.time')
 local log = require('log') -- luacheck: ignore
 
@@ -19,7 +19,7 @@ local index = {
 }
 
 local function update_stat(tube_name, name)
-    statistics.update(tube_name, name, '+', 1)
+    stats.update(tube_name, name, '+', 1)
 end
 
 local function is_expired(task)

sharded_queue/statistics.lua → sharded_queue/stats/storage.lua

@@ -1,3 +1,5 @@
+---- Module used to store storage-specific statistics.
+
 local state = require('sharded_queue.state')
 
 local statistics = {}
@@ -15,7 +17,8 @@ local actions = {
 }
 
 function statistics.init()
-    local space_stat = box.schema.space.create('_queue_statistics', { if_not_exists = true })
+    local space_stat = box.schema.space.create('_queue_statistics',
+        { if_not_exists = true })
     space_stat:format({
         { 'tube_name', 'string' },
         { 'done', 'unsigned' },
@@ -40,7 +43,9 @@ end
 
 function statistics.update(tube_name, stat_name, operation, value)
     if actions[stat_name] == nil then return end
-    box.space._queue_statistics:update(tube_name, { { operation, actions[stat_name], value } })
+
+    box.space._queue_statistics:update(tube_name,
+        { { operation, actions[stat_name], value } })
 end
 
 function statistics.reset(tube_name)

sharded_queue/storage.lua

@@ -4,7 +4,7 @@ local json = require('json')
 local cartridge = require('cartridge')
 
 local state = require('sharded_queue.state')
-local statistics = require('sharded_queue.statistics')
+local stats_storage = require('sharded_queue.stats.storage')
 
 local DEFAULT_DRIVER = 'sharded_queue.drivers.fifottl'
 
@@ -61,7 +61,7 @@ local methods = {
 
 local function apply_config(cfg, opts)
     if opts.is_master then
-        statistics.init()
+        stats_storage.init()
 
         local cfg_tubes = cfg.tubes or {}
 
@@ -76,7 +76,7 @@ local function apply_config(cfg, opts)
                     name = tube_name,
                     options = cfg_tubes[tube_name]
                 })
-                statistics.reset(tube_name)
+                stats_storage.reset(tube_name)
             end
         end
 
@@ -104,7 +104,7 @@ local function apply_config(cfg, opts)
         end
 
         local tube_statistic_func = function(args)
-            return statistics.get(args.tube_name)
+            return stats_storage.get(args.tube_name)
         end
 
         rawset(_G, 'tube_statistic', tube_statistic_func)