Support metrics integration without quantiles

Quantiles computations increases performance overhead by near 10% when
used in statistics. One may want to use statistics with metrics without
quantiles. The patch allows one to do it.

Patch also bumps minimal required metrics rock version.
`metrics >= 0.9.0` is required to use summary quantiles with
age buckets. `metrics >= 0.5.0, < 0.9.0` is unsupported
due to quantile overflow bug [1]. `metrics == 0.9.0` has bug that do
not permits to create summary collector without quantiles [2].
In fact, user may use `metrics >= 0.5.0`, `metrics != 0.9.0`
if he wants to use metrics without quantiles, and `metrics >= 0.9.0`
if he wants to use metrics with quantiles. But this is confusing,
so let's use a single restriction for both cases.

1. tarantool/metrics#235
2. tarantool/metrics#262

Follows up #224

.github/workflows/test_on_push.yaml

@@ -26,7 +26,7 @@ jobs:
           - tarantool-version: "2.8"
             metrics-version: "0.1.8"
           - tarantool-version: "2.8"
-            metrics-version: "0.9.0"
+            metrics-version: "0.10.0"
           - tarantool-version: "2.8"
             coveralls: true
             metrics-version: "0.12.0"

README.md

@@ -606,18 +606,21 @@ crud.disable_stats()
 crud.reset_stats()
 ```
 
-If [`metrics`](https://github.com/tarantool/metrics) `0.9.0` or greater
+If [`metrics`](https://github.com/tarantool/metrics) `0.10.0` or greater
 found, metrics collectors will be used by default to store statistics
 instead of local collectors. You can manually choose driver if needed.
 ```lua
--- Use metrics collectors.
+-- Use metrics collectors. (Default if metrics found).
 crud.enable_stats({ driver = 'metrics' })
 
+-- Use metrics collectors with 0.99 quantile.
+crud.enable_stats({ driver = 'metrics', quantiles = true })
+
 -- Use simple local collectors.
 crud.enable_stats({ driver = 'local' })
 ```
-Performance overhead is 3-5% in case of `local` driver and
-10-20% in case of `metrics` driver.
+Performance overhead is 3-7% in case of `local` driver and
+5-10% in case of `metrics` driver, up to 20% for `metrics` with quantiles.
 
 Format is as follows.
 ```
@@ -668,7 +671,8 @@ Each operation section contains of 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 0.99 quantile of request execution
-time if `metrics` driver used, otherwise `latency` is total average.
+time if `metrics` driver used and quantiles enabled,
+otherwise `latency` is total average.
 `time` is total time of requests execution.
 
 In [`metrics`](https://www.tarantool.io/en/doc/latest/book/monitoring/)

crud/stats/local_registry.lua

@@ -1,23 +1,36 @@
+local errors = require('errors')
+
 local dev_checks = require('crud.common.dev_checks')
 local op_module = require('crud.stats.operation')
 local registry_common = require('crud.stats.registry_common')
 local stash = require('crud.stats.stash')
 
 local registry = {}
-local internal_registry = stash.get('local_registry')
+local internal = stash.get('local_registry')
+local StatsLocalError = errors.new_class('StatsLocalError', {capture_stack = false})
 
 --- Initialize local metrics registry
 --
 --  Registries are not meant to used explicitly
 --  by users, init is not guaranteed to be idempotent.
 --
 -- @function init
+-- @tparam table opts
+--
+--  @tfield boolean quantiles
+--   Quantiles is not supported for local, only `false` is valid.
 --
 -- @treturn boolean Returns true.
 --
-function registry.init()
-    internal_registry.spaces = {}
-    internal_registry.space_not_found = 0
+function registry.init(opts)
+    dev_checks({ quantiles = 'boolean' })
+
+    StatsLocalError:assert(opts.quantiles == false,
+        "Quantiles are not supported for 'local' statistics registry")
+
+    internal.registry = {}
+    internal.registry.spaces = {}
+    internal.registry.space_not_found = 0
 
     return true
 end
@@ -32,7 +45,7 @@ end
 -- @treturn boolean Returns true.
 --
 function registry.destroy()
-    internal_registry = stash.reset('local_registry')
+    internal.registry = nil
 
     return true
 end
@@ -58,10 +71,10 @@ function registry.get(space_name)
     dev_checks('?string')
 
     if space_name ~= nil then
-        return table.deepcopy(internal_registry.spaces[space_name]) or {}
+        return table.deepcopy(internal.registry.spaces[space_name]) or {}
     end
 
-    return table.deepcopy(internal_registry)
+    return table.deepcopy(internal.registry)
 end
 
 --- Check if space statistics are present in registry
@@ -76,7 +89,7 @@ end
 function registry.is_unknown_space(space_name)
     dev_checks('string')
 
-    return internal_registry.spaces[space_name] == nil
+    return internal.registry.spaces[space_name] == nil
 end
 
 --- Increase requests count and update latency info
@@ -101,8 +114,8 @@ end
 function registry.observe(latency, space_name, op, status)
     dev_checks('number', 'string', 'string', 'string')
 
-    registry_common.init_collectors_if_required(internal_registry.spaces, space_name, op)
-    local collectors = internal_registry.spaces[space_name][op][status]
+    registry_common.init_collectors_if_required(internal.registry.spaces, space_name, op)
+    local collectors = internal.registry.spaces[space_name][op][status]
 
     collectors.count = collectors.count + 1
     collectors.time = collectors.time + latency
@@ -118,7 +131,7 @@ end
 -- @treturn boolean Returns true.
 --
 function registry.observe_space_not_found()
-    internal_registry.space_not_found = internal_registry.space_not_found + 1
+    internal.registry.space_not_found = internal.registry.space_not_found + 1
 
     return true
 end
@@ -142,8 +155,8 @@ function registry.observe_fetch(tuples_fetched, tuples_lookup, space_name)
     dev_checks('number', 'number', 'string')
 
     local op = op_module.SELECT
-    registry_common.init_collectors_if_required(internal_registry.spaces, space_name, op)
-    local collectors = internal_registry.spaces[space_name][op].details
+    registry_common.init_collectors_if_required(internal.registry.spaces, space_name, op)
+    local collectors = internal.registry.spaces[space_name][op].details
 
     collectors.tuples_fetched = collectors.tuples_fetched + tuples_fetched
     collectors.tuples_lookup = collectors.tuples_lookup + tuples_lookup
@@ -167,8 +180,8 @@ function registry.observe_map_reduces(count, space_name)
     dev_checks('number', 'string')
 
     local op = op_module.SELECT
-    registry_common.init_collectors_if_required(internal_registry.spaces, space_name, op)
-    local collectors = internal_registry.spaces[space_name][op].details
+    registry_common.init_collectors_if_required(internal.registry.spaces, space_name, op)
+    local collectors = internal.registry.spaces[space_name][op].details
 
     collectors.map_reduces = collectors.map_reduces + count