api: fix Graphite configuration validation

CHANGELOG.md

@@ -10,6 +10,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Fixed
 
 - Export targets not being stopped after removal from the role configuration (#47).
+- Graphite exporters stop after a configuration reload that keeps the
+  `graphite` section unchanged.
+- Requirement of metrics 1.7.0+ for an empty `graphite` section.
 
 ## 0.4.1 - 2026-05-07
 

roles/metrics-export.lua

@@ -174,13 +174,12 @@ local function validate_graphite_node(endpoint)
     validate_graphite_send_interval(endpoint)
 end
 
-local function validate_graphite(conf)
-    local ok = pcall(require('metrics.plugins.graphite').stop)
-    if not ok then
-        error('ensure you have metrics 1.7.0+ (provided with Tarantool 3.7.0+ or can be ' ..
-            'installed as an external dependency)', 2)
-    end
+local function is_graphite_supported()
+    local ok, graphite = pcall(require, 'metrics.plugins.graphite')
+    return ok and type(graphite) == "table" and type(graphite.stop) == "function"
+end
 
+local function validate_graphite(conf)
     if conf ~= nil and type(conf) ~= "table" then
         error("graphite configuration must be a table, got " .. type(conf), 2)
     end
@@ -190,6 +189,11 @@ local function validate_graphite(conf)
         error("graphite configuration must be an array, not a map", 2)
     end
 
+    if next(conf) ~= nil and not is_graphite_supported() then
+        error('ensure you have metrics 1.7.0+ (provided with Tarantool 3.7.0+ or can be ' ..
+            'installed as an external dependency)', 2)
+    end
+
     for _, graphite_node in ipairs(conf) do
         validate_graphite_node(graphite_node)
     end

test/integration/reload_config_test.lua

@@ -189,6 +189,45 @@ g.test_reload_config_remove_http_target = function(cg)
     t.assert_not(is_tcp_connect('127.0.0.1', 8082))
 end
 
+g.before_test('test_reload_config_remove_graphite_target', function(cg)
+    helpers.skip_if_graphite_unsupported()
+    fio.copyfile(fio.pathjoin('test', 'entrypoint', 'graphite_config.yaml'), cg.workdir)
+end)
+
+g.test_reload_config_remove_graphite_target = function(cg)
+    cg.server = server:new({
+        config_file = fio.pathjoin(cg.workdir, 'graphite_config.yaml'),
+        chdir = cg.workdir,
+        alias = 'master',
+        workdir = cg.workdir,
+    })
+    cg.server:start({wait_until_ready = true})
+    t.assert_ge(graphite_helpers.count_graphite_frames("master", "127.0.0.1", 44444, 1), 1)
+    t.assert_ge(graphite_helpers.count_graphite_frames("tarantool", "127.0.0.1", 2223, 2), 1)
+
+    local config_path = fio.pathjoin(cg.workdir, 'graphite_config.yaml')
+    local file = fio.open(config_path, {'O_RDONLY'})
+    t.assert(file ~= nil)
+    local cfg = yaml.decode(file:read())
+    file:close()
+
+    local role_cfg = cfg.groups['group-001'].replicasets['replicaset-001'].
+        instances.master.roles_cfg['roles.metrics-export']
+    role_cfg.graphite = nil
+
+    file = fio.open(config_path, {
+        'O_CREAT', 'O_WRONLY', 'O_TRUNC',
+    }, tonumber('644', 8))
+    t.assert(file ~= nil)
+    file:write(yaml.encode(cfg))
+    file:close()
+
+    cg.server:eval("require('config'):reload()")
+
+    t.assert_equals(graphite_helpers.count_graphite_frames("master", "127.0.0.1", 44444, 1), 0)
+    t.assert_equals(graphite_helpers.count_graphite_frames("tarantool", "127.0.0.1", 2223, 2), 0)
+end
+
 local function change_graphite_port_in_config(cg, new_port)
     if new_port == nil then
         new_port = '2222'
@@ -241,3 +280,27 @@ g.test_reload_config_graphite = function(cg)
     t.assert_ge(graphite_helpers.count_graphite_frames("tarantool", "127.0.0.1", 3333, 2), 1)
     t.assert_equals(graphite_helpers.count_graphite_frames("tarantool", "127.0.0.1", 2223, 2), 0)
 end
+
+g.before_test('test_reload_config_graphite_not_changed', function(cg)
+    helpers.skip_if_graphite_unsupported()
+    fio.copyfile(fio.pathjoin('test', 'entrypoint', 'graphite_config.yaml'), cg.workdir)
+end)
+
+g.test_reload_config_graphite_not_changed = function(cg)
+    cg.server = server:new({
+        config_file = fio.pathjoin(cg.workdir, 'graphite_config.yaml'),
+        chdir = cg.workdir,
+        alias = 'master',
+        workdir = cg.workdir,
+    })
+
+    cg.server:start({wait_until_ready = true})
+
+    t.assert_ge(graphite_helpers.count_graphite_frames("master", "127.0.0.1", 44444, 1), 1)
+
+    -- Reload the same configuration: the running exporters must survive it.
+    cg.server:eval("require('config'):reload()")
+
+    t.assert_ge(graphite_helpers.count_graphite_frames("master", "127.0.0.1", 44444, 1), 1)
+    t.assert_ge(graphite_helpers.count_graphite_frames("tarantool", "127.0.0.1", 2223, 2), 1)
+end

test/unit/validate_test.lua

@@ -1044,6 +1044,11 @@ local ok_cases = {
             },
         },
     },
+    ["graphite_empty"] = {
+        cfg = {
+            graphite = {},
+        },
+    },
     ["graphite_full"] = {
         cfg = {
             graphite = {{
@@ -1084,7 +1089,9 @@ local ok_cases = {
 
 for name, case in pairs(ok_cases) do
     g["test_validate_ok_" .. name] = function(gc)
-        if (case.cfg or {}).graphite ~= nil then
+        if next((case.cfg or {}).graphite or {}) ~= nil then
+            -- Skip if at least one endpoint exists. Empty table could
+            -- be possible.
             helpers.skip_if_graphite_unsupported()
         end