Add schema reload counter to stats

Add counter of schema reloads in calls to module statistics. Schema
reloads are counted over all spaces and stored in top level, like
`space_not_found` counter.

```
crud.stats().schema_reloads
---
- 2
...

```

In metrics, they are stored in `tnt_crud_schema_reloads` counter.

Part of #224

README.md

@@ -622,6 +622,7 @@ crud.stats()
           count: 4
           time: 0.000004
   space_not_found: 0
+  schema_reloads: 0
 ...
 crud.stats('my_space')
 ---
@@ -642,7 +643,9 @@ field will be empty. If no operations has been called for a
 space, it will not be represented. Operations called for
 spaces not found both on storages and in statistics registry
 (including cases when crud can't verify space existence)
-will increment `space_not_found` counter.
+will increment `space_not_found` counter. Operation calls
+that reloaded a schema will increment `schema_reloads`
+counter.
 
 Possible statistics operation labels are
 `insert` (for `insert` and `insert_object` calls),

crud/common/schema.lua

@@ -9,6 +9,7 @@ local ReloadSchemaError = errors.new_class('ReloadSchemaError', {capture_stack =
 
 local const = require('crud.common.const')
 local dev_checks = require('crud.common.dev_checks')
+local fiber_context = require('crud.common.fiber_context')
 
 local schema = {}
 
@@ -103,6 +104,13 @@ function schema.wrap_func_reload(func, ...)
         end
     end
 
+    local context_stats = fiber_context.init_section('router_stats')
+    if context_stats.schema_reloads == nil then
+        context_stats.schema_reloads = i
+    else
+        context_stats.schema_reloads = context_stats.schema_reloads + i
+    end
+
     return res, err
 end
 

crud/stats/local_registry.lua

@@ -23,6 +23,7 @@ function registry.init()
     internal.registry = {}
     internal.registry.spaces = {}
     internal.registry.space_not_found = 0
+    internal.registry.schema_reloads = 0
 
     return true
 end
@@ -180,4 +181,21 @@ function registry.observe_map_reduces(count, space_name)
     return true
 end
 
+--- Increase statistics of schema reloads
+--
+-- @function observe_schema_reloads
+--
+-- @tparam number count
+--  Schema reloads performed.
+--
+-- @treturn boolean Returns true.
+--
+function registry.observe_schema_reloads(count)
+    dev_checks('number')
+
+    internal.registry.schema_reloads = internal.registry.schema_reloads + count
+
+    return true
+end
+
 return registry

crud/stats/module.lua

@@ -184,6 +184,10 @@ local function wrap_tail(space_name, op, pairs, start_time, call_status, ...)
             registry.observe_map_reduces(context_stats.map_reduces, space_name)
         end
 
+        if context_stats.schema_reloads ~= nil then
+            registry.observe_schema_reloads(context_stats.schema_reloads)
+        end
+
         fiber_context.drop_section('router_stats')
     end
 

test/entrypoint/srv_stats.lua

@@ -40,6 +40,45 @@ package.preload['customers-storage'] = function()
                 unique = false,
                 if_not_exists = true,
             })
+
+            rawset(_G, 'create_space', function()
+                local change_customers_space = box.schema.space.create('change_customers', {
+                    format = {
+                        {name = 'id', type = 'unsigned'},
+                        {name = 'bucket_id', type = 'unsigned'},
+                        {name = 'value', type = 'string'},
+                    },
+                    if_not_exists = true,
+                    engine = engine,
+                })
+
+                -- primary index
+                change_customers_space:create_index('id_index', {
+                    parts = { {field = 'id'} },
+                    if_not_exists = true,
+                })
+            end)
+
+            rawset(_G, 'create_bucket_id_index', function()
+                box.space.change_customers:create_index('bucket_id', {
+                    parts = { {field = 'bucket_id'} },
+                    if_not_exists = true,
+                    unique = false,
+                })
+            end)
+
+            rawset(_G, 'set_value_type_to_unsigned', function()
+                local new_format = {}
+
+                for _, field_format in ipairs(box.space.change_customers:format()) do
+                    if field_format.name == 'value' then
+                        field_format.type = 'unsigned'
+                    end
+                    table.insert(new_format, field_format)
+                end
+
+                box.space.change_customers:format(new_format)
+            end)
         end,
     }
 end

test/integration/stats_test.lua

@@ -11,6 +11,7 @@ local space_id = 542
 local space_name = 'customers'
 local unknown_space_name = 'non_existing_space'
 local new_space_name = 'newspace'
+local schema_change_space_name = 'change_customers'
 
 g.before_all(function(g)
     g.cluster = helpers.Cluster:new({
@@ -37,6 +38,7 @@ g.before_each(function(g)
     g.router:eval("crud = require('crud')")
     helpers.truncate_space_on_cluster(g.cluster, space_name)
     helpers.drop_space_on_cluster(g.cluster, new_space_name)
+    helpers.drop_space_on_cluster(g.cluster, schema_change_space_name)
 end)
 
 function g:get_stats(space_name)
@@ -724,3 +726,48 @@ g.test_spaces_dropped_in_runtime_supported_with_stats = function(g)
     t.assert_equals(op_after.error.count - op_before.error.count, 1,
         "Error requests count incremented since space was known to registry before drop")
 end
+
+
+-- luacheck: max comment line length 150
+-- Based on https://github.com/tarantool/crud/blob/76e33749226d5fd1195e2628502a9e01d6a616fa/test/integration/updated_shema_test.lua#L622
+local function perform_insert_call_with_schema_reload(g)
+    -- create space w/ bucket_id index
+    helpers.call_on_servers(g.cluster, {'s1-master', 's2-master'}, function(server)
+        server.net_box:call('create_space')
+        server.net_box:call('create_bucket_id_index')
+    end)
+
+    -- value should be string error
+    local obj, err = g.router:call(
+        'crud.insert_object', { schema_change_space_name, { id = 11, value = 123 } }
+    )
+
+    t.assert_equals(obj, nil)
+    t.assert_is_not(err, nil)
+    t.assert_str_contains(err.err, "type does not match one required by operation: expected string")
+
+    -- set value type to unsigned
+    helpers.call_on_servers(g.cluster, {'s1-master', 's2-master'}, function(server)
+        server.net_box:call('set_value_type_to_unsigned')
+    end)
+
+    -- check that schema changes were applied
+    -- insert value unsigned - OK
+    local obj, err = g.router:call(
+       'crud.insert_object', { schema_change_space_name, { id = 11, value = 123 } }
+    )
+
+    t.assert_is_not(obj, nil)
+    t.assert_equals(err, nil)
+end
+
+g.test_call_with_schema_reload_increments_counter = function(g)
+    local stats_before = g:get_stats()
+
+    perform_insert_call_with_schema_reload(g)
+
+    local stats_after = g:get_stats()
+
+    t.assert_gt(stats_after.schema_reloads, stats_before.schema_reloads,
+        "Schema reloads counter incremented")
+end

test/unit/stats_test.lua

@@ -530,6 +530,20 @@ g.test_map_reduce_increment = function(g)
         "Counter of map reduces incremented")
 end
 
+g.test_schema_reload = function(g)
+    local op = stats_module.op.INSERT
+    local inc = 1
+
+    local _, err = g.router:eval(eval_with_fiber_context_setup,
+        { op, space_name, 'schema_reloads', inc })
+    t.assert_equals(err, nil)
+
+    local stats = g:get_stats()
+
+    t.assert_equals(stats.schema_reloads, inc,
+        "Counter of map reduces incremented")
+end
+
 g.test_resolve_name_from_id = function(g)
     local op = stats_module.op.LEN
     g.router:eval(call_wrapped, { 'return_true', stats_module.op.LEN, {}, space_id })