Add pause/resume feature for hotreloading (#1784)

Co-authored-by: Igor Zolotarev <[email protected]>

CHANGELOG.rst

@@ -61,6 +61,8 @@ Added
 
 - Allow to pause failover at runtime, with Lua API and GraphQL (#1763).
 
+- Allow to block roles reload at runtime, with Lua API (#1219).
+
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 Changed
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

cartridge/roles.lua

@@ -32,6 +32,7 @@ vars:new('roles_by_number', {})
 vars:new('roles_by_role_name', {})
 vars:new('roles_by_module_name', {})
 vars:new('implicit_roles')
+vars:new('pause', false)
 
 -- Don't put it as default var value to allow overriding
 -- after hot-reload (hypothetically)
@@ -541,6 +542,8 @@ end
 -- usual with `validate_config()`, `init()`, and `apply_config()`
 -- callbacks.
 --
+-- Hot-reload could be forbidden in runtime with `forbid_reload` function.
+--
 -- @function reload
 -- @treturn[1] boolean true
 -- @treturn[2] nil
@@ -552,6 +555,12 @@ local function reload()
         )
     end
 
+    if vars.pause == true then
+        return nil, ReloadError:new(
+            'Reloading roles forbidden'
+        )
+    end
+
     local confapplier = require('cartridge.confapplier')
     local state = confapplier.get_state()
     if state ~= 'RolesConfigured'
@@ -595,6 +604,38 @@ local function reload()
     return confapplier.apply_config(clusterwide_config)
 end
 
+--- Forbid hot-reload of cartridge roles code.
+--
+-- @function forbid_reload
+-- @treturn[1] boolean true
+-- @treturn[2] nil
+-- @treturn[2] table Error description
+local function forbid_reload()
+    log.info('Forbid reload roles')
+    vars.pause = true
+end
+
+--- Allow hot-reload of cartridge roles code.
+--
+-- @function allow_reload
+-- @treturn[1] boolean true
+-- @treturn[2] nil
+-- @treturn[2] table Error description
+local function allow_reload()
+    log.info('Allow reload roles')
+    vars.pause = false
+end
+
+--- Returns true if hot-reload of cartridge roles code is forbidden.
+--
+-- @function is_reload_forbidden
+-- @treturn[1] boolean true
+-- @treturn[2] nil
+-- @treturn[2] table Error description
+local function is_reload_forbidden()
+    return vars.pause == true
+end
+
 return {
     cfg = cfg,
     get_role = get_role,
@@ -608,4 +649,8 @@ return {
     apply_config = apply_config,
     reload = reload,
     stop = stop,
+
+    forbid_reload = forbid_reload,
+    allow_reload = allow_reload,
+    is_reload_forbidden = is_reload_forbidden,
 }

test/hotreload/pause_test.lua

@@ -0,0 +1,52 @@
+local fio = require('fio')
+local t = require('luatest')
+local g = t.group()
+
+local helpers = require('test.helper')
+
+g.before_all(function()
+    g.cluster = helpers.Cluster:new({
+        datadir = fio.tempdir(),
+        use_vshard = false,
+        server_command = helpers.entrypoint('srv_basic'),
+        cookie = helpers.random_cookie(),
+        replicasets = {{alias = 'A', roles = {}, servers = 1}},
+    })
+    g.cluster:start()
+end)
+
+g.after_all(function()
+    g.cluster:stop()
+    fio.rmtree(g.cluster.datadir)
+end)
+
+function g.test_errors()
+    local _ = g.cluster.main_server:exec(function()
+        package.loaded['cartridge.roles'].forbid_reload()
+    end)
+
+    local ok = g.cluster.main_server:exec(function()
+        return package.loaded['cartridge.roles'].is_reload_forbidden()
+    end)
+    t.assert_equals(ok, true)
+
+    local ok, err = g.cluster.main_server.net_box:call(
+        'package.loaded.cartridge.reload_roles'
+    )
+
+    t.assert_equals(ok, nil)
+    t.assert_covers(err, {
+        class_name = 'HotReloadError',
+        err = 'Reloading roles forbidden',
+    })
+
+    local _ = g.cluster.main_server:exec(function()
+        package.loaded['cartridge.roles'].allow_reload()
+    end)
+
+    local ok, err = g.cluster.main_server.net_box:call(
+        'package.loaded.cartridge.reload_roles'
+    )
+    t.assert_equals(ok, true)
+    t.assert_equals(err, nil)
+end