Add statistics for all CRUD operations on router

Add statistics module for collecting metrics of CRUD operations on
router. Wrap all CRUD operation calls in statistics collector.
Statistics may be disabled and re-enabled. Some internal methods of
select/pairs were reworked or extended to provide statistics info.
`cursor` returned from storage on select/pairs now contains stats of
tuple count and lookup count. All changes are backward-compatible and
should work even with older versions of crud routers and storages.

Part of #224

Author: DifferentialOrange

CHANGELOG.md

@@ -8,6 +8,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 ## [Unreleased]
 
 ### Added
+* Statistics for all CRUD operations on router (#224).
 
 ### Changed
 

README.md

@@ -586,6 +586,63 @@ crud.len('customers')
 ...
 ```
 
+### Statistics
+
+`crud` routers provide statistics on called operations.
+```lua
+-- Returns table with statistics information.
+crud.stats()
+```
+
+Statistics collect enabled by default on all routers.
+It can be disabled and re-enabled later.
+```lua
+-- Disables statistics collect and resets all collectors.
+crud.disable_stats()
+
+-- Enable statistics collect and recreates all collectors.
+crud.enable_stats()
+```
+
+Enabling stats on non-router instances is meaningless.
+
+`crud.stats()` contains several sections: `insert` (for `insert` and `insert_object` calls),
+`get`, `replace`  (for `replace` and `replace_object` calls), `update`,
+`upsert` (for `upsert` and `upsert_object` calls), `delete`,
+`select` (for `select` and `pairs` calls), `truncate`, `len` and
+`borders` (for `min` and `max` calls).
+
+```lua
+crud.stats()['insert']
+---
+- ok:
+    latency: 0.002
+    count: 19800
+  error:
+    latency: 0.000001
+    count: 4
+---
+```
+Each section contains different collectors for success calls
+and error (both error throw and `nil, err`) returns. `count`
+is total requests count since instance start or stats restart.
+`latency` is execution time of last request.
+
+Additionally, `select` section contains `details` collectors.
+```lua
+crud.stats()['select']['details']
+---
+- map_reduces_planned: 4
+  tuples_fetched: 10500
+  tuples_lookup: 2380000
+...
+```
+`map_reduces_planned` is a count of planned map reduces
+(including those not executed successfully). `tuples_fetched`
+is a count of tuples fetched from storages during execution,
+`tuples_lookup` is a count of tuples looked up on storages
+while collecting response for call.
+
 ## Cartridge roles
 
 `cartridge.roles.crud-storage` is a Tarantool Cartridge role that depends on the

crud.lua

@@ -14,6 +14,7 @@ local len = require('crud.len')
 local borders = require('crud.borders')
 local sharding_key = require('crud.common.sharding_key')
 local utils = require('crud.common.utils')
+local stats = require('crud.stats.module')
 
 local crud = {}
 
@@ -22,67 +23,67 @@ local crud = {}
 
 -- @refer insert.tuple
 -- @function insert
-crud.insert = insert.tuple
+crud.insert = stats.wrap(insert.tuple, stats.label.INSERT)
 
 -- @refer insert.object
 -- @function insert_object
-crud.insert_object = insert.object
+crud.insert_object = stats.wrap(insert.object, stats.label.INSERT)
 
 -- @refer get.call
 -- @function get
-crud.get = get.call
+crud.get = stats.wrap(get.call, stats.label.GET)
 
 -- @refer replace.tuple
 -- @function replace
-crud.replace = replace.tuple
+crud.replace = stats.wrap(replace.tuple, stats.label.REPLACE)
 
 -- @refer replace.object
 -- @function replace_object
-crud.replace_object = replace.object
+crud.replace_object = stats.wrap(replace.object, stats.label.REPLACE)
 
 -- @refer update.call
 -- @function update
-crud.update = update.call
+crud.update = stats.wrap(update.call, stats.label.UPDATE)
 
 -- @refer upsert.tuple
 -- @function upsert
-crud.upsert = upsert.tuple
+crud.upsert = stats.wrap(upsert.tuple, stats.label.UPSERT)
 
 -- @refer upsert.object
 -- @function upsert
-crud.upsert_object = upsert.object
+crud.upsert_object = stats.wrap(upsert.object, stats.label.UPSERT)
 
 -- @refer delete.call
 -- @function delete
-crud.delete = delete.call
+crud.delete = stats.wrap(delete.call, stats.label.DELETE)
 
 -- @refer select.call
 -- @function select
-crud.select = select.call
+crud.select = stats.wrap(select.call, stats.label.SELECT)
 
 -- @refer select.pairs
 -- @function pairs
-crud.pairs = select.pairs
+crud.pairs = stats.wrap_pairs(select.pairs, stats.label.SELECT)
 
 -- @refer utils.unflatten_rows
 -- @function unflatten_rows
 crud.unflatten_rows = utils.unflatten_rows
 
 -- @refer truncate.call
 -- @function truncate
-crud.truncate = truncate.call
+crud.truncate = stats.wrap(truncate.call, stats.label.TRUNCATE)
 
 -- @refer len.call
 -- @function len
-crud.len = len.call
+crud.len = stats.wrap(len.call, stats.label.LEN)
 
 -- @refer borders.min
 -- @function min
-crud.min = borders.min
+crud.min = stats.wrap(borders.min, stats.label.BORDERS)
 
 -- @refer borders.max
 -- @function max
-crud.max = borders.max
+crud.max = stats.wrap(borders.max, stats.label.BORDERS)
 
 -- @refer utils.cut_rows
 -- @function cut_rows
@@ -92,6 +93,18 @@ crud.cut_rows = utils.cut_rows
 -- @function cut_objects
 crud.cut_objects = utils.cut_objects
 
+-- @refer stats.get
+-- @function stats
+crud.stats = stats.get
+
+-- @refer stats.enable
+-- @function enable_stats
+crud.enable_stats = stats.enable
+
+-- @refer stats.disable
+-- @function disable_stats
+crud.disable_stats = stats.disable
+
 --- Initializes crud on node
 --
 -- Exports all functions that are used for calls
@@ -118,11 +131,13 @@ function crud.init_storage()
 end
 
 function crud.init_router()
-   rawset(_G, 'crud', crud)
+    rawset(_G, 'crud', crud)
+    stats.enable()
 end
 
 function crud.stop_router()
     rawset(_G, 'crud', nil)
+    stats.disable()
 end
 
 function crud.stop_storage()

crud/common/utils.lua

@@ -606,4 +606,8 @@ function utils.merge_options(opts_a, opts_b)
     return fun.chain(opts_a or {}, opts_b or {}):tomap()
 end
 
+function utils.pass()
+    -- Do nothing.
+end
+
 return utils

crud/select.lua

@@ -59,7 +59,7 @@ local function select_on_storage(space_name, index_id, conditions, opts)
     end
 
     -- execute select
-    local tuples, err = select_executor.execute(space, index, filter_func, {
+    local res, err = select_executor.execute(space, index, filter_func, {
         scan_value = opts.scan_value,
         after_tuple = opts.after_tuple,
         tarantool_iter = opts.tarantool_iter,
@@ -70,15 +70,18 @@ local function select_on_storage(space_name, index_id, conditions, opts)
     end
 
     local cursor
-    if #tuples < opts.limit or opts.limit == 0 then
+    if res.stats.tuples_fetched < opts.limit or opts.limit == 0 then
         cursor = {is_end = true}
     else
-        cursor = make_cursor(tuples)
+        cursor = make_cursor(res.tuples)
     end
 
+    -- Pass statistics data from storage with cursor.
+    cursor.stats = res.stats
+
     -- getting tuples with user defined fields (if `fields` option is specified)
     -- and fields that are needed for comparison on router (primary key + scan key)
-    return cursor, schema.filter_tuples_fields(tuples, opts.field_names)
+    return cursor, schema.filter_tuples_fields(res.tuples, opts.field_names)
 end
 
 function select_module.init()

crud/select/compat/select.lua

@@ -8,6 +8,7 @@ local dev_checks = require('crud.common.dev_checks')
 local common = require('crud.select.compat.common')
 local schema = require('crud.common.schema')
 local sharding_key_module = require('crud.common.sharding_key')
+local stats = require('crud.stats.module')
 
 local compare_conditions = require('crud.compare.conditions')
 local select_plan = require('crud.select.plan')
@@ -111,6 +112,11 @@ local function build_select_iterator(space_name, user_conditions, opts)
         if err ~= nil then
             return nil, err, true
         end
+    else
+        -- Use function call to collect map reduce count instead
+        -- of passing values outside to wrapper to not break
+        -- pairs api with excessice context values in return.
+        stats.inc_map_reduce_count()
     end
 
     local tuples_limit = opts.first
@@ -142,7 +148,12 @@ local function build_select_iterator(space_name, user_conditions, opts)
     local merger = Merger.new(replicasets_to_select, space, plan.index_id,
             common.SELECT_FUNC_NAME,
             {space_name, plan.index_id, plan.conditions, select_opts},
-            {tarantool_iter = plan.tarantool_iter, field_names = plan.field_names, call_opts = opts.call_opts}
+            {
+                tarantool_iter = plan.tarantool_iter,
+                field_names = plan.field_names,
+                call_opts = opts.call_opts,
+                stats_callback = stats.get_fetch_callback(),
+            }
         )
 
     -- filter space format by plan.field_names (user defined fields + primary key + scan key)

crud/select/compat/select_old.lua

@@ -9,6 +9,7 @@ local sharding = require('crud.common.sharding')
 local dev_checks = require('crud.common.dev_checks')
 local schema = require('crud.common.schema')
 local sharding_key_module = require('crud.common.sharding_key')
+local stats = require('crud.stats.module')
 
 local compare_conditions = require('crud.compare.conditions')
 local select_plan = require('crud.select.plan')
@@ -30,6 +31,7 @@ local function select_iteration(space_name, plan, opts)
     })
 
     local call_opts = opts.call_opts
+    local stats_callback = stats.get_fetch_callback()
 
     -- call select on storages
     local storage_select_opts = {
@@ -59,6 +61,14 @@ local function select_iteration(space_name, plan, opts)
 
     local tuples = {}
     for replicaset_uuid, replicaset_results in pairs(results) do
+        -- Stats extracted with callback here and not passed
+        -- outside to wrapper because fetch for pairs can be
+        -- called even after pairs() return from generators.
+        local cursor = replicaset_results[1]
+        if cursor.stats ~= nil then
+            stats_callback(cursor.stats)
+        end
+
         tuples[replicaset_uuid] = replicaset_results[2]
     end
 
@@ -137,6 +147,11 @@ local function build_select_iterator(space_name, user_conditions, opts)
         if err ~= nil then
             return nil, err, true
         end
+    else
+        -- Use function call to collect map reduce count instead
+        -- of passing values outside to wrapper to not break
+        -- pairs api with excessice context values in return.
+        stats.inc_map_reduce_count()
     end
 
     -- generate tuples comparator

crud/select/executor.lua

@@ -69,7 +69,13 @@ function executor.execute(space, index, filter_func, opts)
     opts = opts or {}
 
     if opts.limit == 0 then
-        return {}
+        return {
+            tuples = {},
+            stats = {
+                tuples_fetched = 0,
+                tuples_lookup = 0,
+            },
+        }
     end
 
     local tuples = {}
@@ -94,14 +100,21 @@ function executor.execute(space, index, filter_func, opts)
         end
 
         if tuple == nil then
-            return {}
+            return {
+                tuples = {},
+                stats = {
+                    tuples_fetched = 0,
+                    tuples_lookup = 0,
+                },
+            }
         end
     end
 
     if tuple == nil then
         gen.state, tuple = gen(gen.param, gen.state)
     end
 
+    local lookup_count = 0
     while true do
         if tuple == nil then
             break
@@ -121,9 +134,16 @@ function executor.execute(space, index, filter_func, opts)
         end
 
         gen.state, tuple = gen(gen.param, gen.state)
+        lookup_count = lookup_count + 1
     end
 
-    return tuples
+    return {
+        tuples = tuples,
+        stats = {
+            tuples_fetched = #tuples,
+            tuples_lookup = lookup_count,
+        },
+    }
 end
 
 return executor