config: expand config:info()

Closes tarantool#9780

@TarantoolBot document
Title: Expansion of `config:info()`

Before this patch, the `meta` field of the `config:info()` function
contained the meta data of the last load, even if it was unsuccessful
reload. This can be inconvenient because if the reload fails, we expect
that the last configuration that was successfully applied is used, but
its metadata was lost.

Now `config:info()` can take one argument — the version of the
information that should be returned by the function. If no arguments are
specified or the argument is the string `v1`, the return value has the
same structure as before. If the argument is the string `v2`, the `meta`
field in the return value has fields - `active` (meta for the last
successfully applied configuration) and `last` (meta of the last loaded
configuration). Currently only these values are accepted.

changelogs/unreleased/gh-9780-show-active-meta.md

@@ -0,0 +1,3 @@
+## feature/config
+
+* The `config:info()` functionality has been expanded (gh-9780).

src/box/lua/config/init.lua

@@ -408,6 +408,9 @@ function methods._startup(self, instance_name, config_file)
         self:_apply_on_startup({phase = 2})
     end
     self:_set_status_based_on_alerts()
+    if self._status == 'ready' or self._status == 'check_warnings' then
+        self._active_metadata = self._metadata
+    end
 
     self:_post_apply()
     self:_set_status_based_on_alerts()
@@ -450,6 +453,9 @@ function methods._reload_noexc(self, opts)
         self:_store(self:_collect(opts))
         self:_apply()
         self:_set_status_based_on_alerts()
+        if self._status == 'ready' or self._status == 'check_warnings' then
+            self._active_metadata = self._metadata
+        end
         self:_post_apply()
     end, opts)
 
@@ -474,13 +480,26 @@ function methods.reload(self)
     end
 end
 
-function methods.info(self)
+function methods.info(self, version)
     selfcheck(self, 'info')
-    return {
-        alerts = self._aboard:alerts(),
-        meta = self._metadata,
-        status = self._status,
-    }
+    if version == nil or version == 'v1' then
+        return {
+            alerts = self._aboard:alerts(),
+            meta = self._metadata,
+            status = self._status,
+        }
+    end
+    if version == 'v2' then
+        return {
+            alerts = self._aboard:alerts(),
+            meta = {
+                active = self._active_metadata,
+                last = self._metadata,
+            },
+            status = self._status,
+        }
+    end
+    error(('Expected "v2" or nil as info version, got %q'):format(version), 0)
 end
 
 -- The object is a singleton. The constructor should be called

test/config-luatest/config_test.lua

@@ -1393,3 +1393,180 @@ g.test_non_dynamic_alert = function(g)
         end,
     })
 end
+
+-- Check that config:info('v2') works properly.
+g.test_info_new_version = function(g)
+    local dir = treegen.prepare_directory(g, {}, {})
+
+    local config = [[
+        credentials:
+          users:
+            guest:
+              roles:
+              - super
+
+        iproto:
+          listen:
+            - uri: unix/:./{{ instance_name }}.iproto
+
+        groups:
+          group-001:
+            replicasets:
+              replicaset-001:
+                instances:
+                  instance-001: {}
+    ]]
+    treegen.write_script(dir, 'config.yaml', config)
+
+    -- New source that sets meta.
+    local script = string.dump(function()
+        local yaml = require('yaml')
+        local file = require('internal.config.utils.file')
+
+        local methods = {}
+        local mt = {
+            __index = methods,
+        }
+
+        function methods.sync(self, config)
+            local data = file.universal_read('myconf.yaml', 'my config file')
+            local ok, res = pcall(yaml.decode, data)
+            if not ok then
+                error('Unable to parse my config file')
+            end
+            self._values = res
+            config:_meta('myconf', 'revision', self._revision)
+            self._revision = self._revision + 1
+        end
+
+        function methods.get(self)
+            return self._values
+        end
+
+        local function new()
+            return setmetatable({
+                name = 'myfile',
+                type = 'instance',
+                _values = {},
+                _revision = 1,
+            }, mt)
+        end
+
+        return {
+            new = new,
+        }
+    end)
+    treegen.write_script(dir, 'source.lua', script)
+
+    local myconf = [[
+        sql:
+          cache_size: 12345
+    ]]
+    treegen.write_script(dir, 'myconf.yaml', myconf)
+
+    local opts = {
+        config_file = 'config.yaml',
+        alias = 'instance-001',
+        chdir = dir,
+    }
+    g.server = server:new(opts)
+    g.server:start()
+
+    -- Make sure the new source is loaded properly and the meta is set.
+    g.server:exec(function()
+        local config = require('config')
+        t.assert_equals(config:get('sql.cache_size'), 5242880)
+
+        config:_register_source(require('source').new())
+        config:reload()
+        t.assert_equals(config:get('sql.cache_size'), 12345)
+        local exp = {
+            myconf = {
+                revision = 1,
+            },
+        }
+        t.assert_equals(config:info().meta, exp)
+        t.assert_equals(config:info('v1').meta, exp)
+        exp = {
+            active = {
+                myconf = {
+                    revision = 1,
+                },
+            },
+            last = {
+                myconf = {
+                    revision = 1,
+                },
+            },
+        }
+        t.assert_equals(config:info('v2').meta, exp)
+    end)
+
+    -- Make sure the meta for config:info() is new and that config:info('v2')
+    -- contains both applied meta and unapplied new meta when reload failed.
+    myconf = [[
+        sql:
+          cache_size: true
+    ]]
+    treegen.write_script(dir, 'myconf.yaml', myconf)
+    g.server:exec(function()
+        local config = require('config')
+        t.assert_equals(config:get('sql.cache_size'), 12345)
+        pcall(config.reload, config)
+        t.assert_equals(config:get('sql.cache_size'), 12345)
+        local exp = {
+            myconf = {
+                revision = 2,
+            },
+        }
+        t.assert_equals(config:info().meta, exp)
+        t.assert_equals(config:info('v1').meta, exp)
+        exp = {
+            active = {
+                myconf = {
+                    revision = 1,
+                },
+            },
+            last = {
+                myconf = {
+                    revision = 2,
+                },
+            },
+        }
+        t.assert_equals(config:info('v2').meta, exp)
+    end)
+
+    -- Make sure that in config:info('v2') both applied meta and unapplied new
+    -- meta are equal when reload is successful.
+    myconf = [[
+        sql:
+          cache_size: 100000
+    ]]
+    treegen.write_script(dir, 'myconf.yaml', myconf)
+    g.server:exec(function()
+        local config = require('config')
+        t.assert_equals(config:get('sql.cache_size'), 12345)
+        config:reload()
+        t.assert_equals(config:get('sql.cache_size'), 100000)
+        local exp = {
+            myconf = {
+                revision = 3,
+            },
+        }
+        t.assert_equals(config:info().meta, exp)
+        t.assert_equals(config:info('v1').meta, exp)
+        exp = {
+            active = {
+                myconf = {
+                    revision = 3,
+                },
+            },
+            last = {
+                myconf = {
+                    revision = 3,
+                },
+            },
+        }
+        t.assert_equals(config:info('v2').meta, exp)
+    end)
+end