Migrate cluster module and adapt it

The original `cluster` module
(tarantool/test/config-luatest/cluster.lua) has been moved to the
current project and will be available as follows:

```lua
local t = require('luatest')
local cluster = t.cluster:new(...)

cluster:start()
```

It is used to simplify managing Tarantool clusters based on the provided
configuration. The helper requires Tarantool 3.0.0 or newer. Otherwise
cluster methods cause an error.

Original helper created by: [email protected]
Test author: [email protected]

Closes #368

CHANGELOG.md

@@ -23,6 +23,7 @@
 - Fix error trace reporting for functions executed with `Server:exec()`
   (gh-396).
 - Remove pretty-printing of `luatest.log` arguments.
+- Add `cluster` helper as a tool for managing a Tarantool cluster (gh-368).
 
 ## 1.0.1
 

config.ld

@@ -10,7 +10,8 @@ file = {
     'luatest/justrun.lua',
     'luatest/cbuilder.lua',
     'luatest/hooks.lua',
-    'luatest/treegen.lua'
+    'luatest/treegen.lua',
+    'luatest/cluster.lua'
 }
 topics = {
     'CHANGELOG.md',

luatest/cluster.lua

@@ -0,0 +1,355 @@
+--- Tarantool 3.0+ cluster management utils.
+--
+-- The helper is used to automatically collect a set of
+-- instances from the provided configuration and automatically
+-- set up servers per each configured instance.
+--
+-- @usage
+--
+-- local cluster = Cluster:new(config)
+-- cluster:start()
+-- cluster['instance-001']:exec(<...>)
+-- cluster:each(function(server)
+--     server:exec(<...>)
+-- end)
+--
+-- After setting up a cluster object the following methods could
+-- be used to interact with it:
+--
+-- * :start() Startup the cluster.
+-- * :start_instance() Startup a specific instance.
+-- * :stop() Stop the cluster.
+-- * :each() Execute a function on each instance.
+-- * :size() get an amount of instances
+-- * :drop() Drop the cluster.
+-- * :sync() Sync the configuration and collect a new set of
+--   instances
+-- * :reload() Reload the configuration.
+--
+-- The module can also be used for testing failure startup
+-- cases:
+--
+-- cluster:startup_error(config, error_message)
+--
+-- @module luatest.cluster
+
+local fun = require('fun')
+local yaml = require('yaml')
+local assertions = require('luatest.assertions')
+local helpers = require('luatest.helpers')
+local hooks = require('luatest.hooks')
+local treegen = require('luatest.treegen')
+local justrun = require('luatest.justrun')
+local server = require('luatest.server')
+
+local Cluster = require('luatest.class').new()
+
+-- Cluster uses custom __index implementation to support
+-- getting instances from it using `cluster['i-001']`.
+--
+-- Thus, we need to change the metatable of the class
+-- with a custom __index method.
+local mt = getmetatable(Cluster)
+mt.__index = function(self, k)
+    local method = rawget(mt, k)
+    if method ~= nil then
+        return method
+    end
+
+    local server_map = rawget(self, '_server_map')
+    if server_map ~= nil and server_map[k] ~= nil then
+        return server_map[k]
+    end
+
+    return rawget(self, k)
+end
+
+local cluster = {
+    _group = {}
+}
+
+function Cluster:inherit(object)
+    setmetatable(object, self)
+    self.__index = self
+    return object
+end
+
+local function init(g)
+    cluster._group = g
+end
+
+-- Stop all the managed instances using <server>:drop().
+local function drop(g)
+    if g._cluster ~= nil then
+        g._cluster:drop()
+    end
+    g._cluster = nil
+end
+
+local function clean(g)
+    assert(g._cluster == nil)
+end
+
+-- {{{ Helpers
+
+-- Collect names of all the instances defined in the config
+-- in the alphabetical order.
+local function instance_names_from_config(config)
+    local instance_names = {}
+    for _, group in pairs(config.groups or {}) do
+        for _, replicaset in pairs(group.replicasets or {}) do
+            for name, _ in pairs(replicaset.instances or {}) do
+                table.insert(instance_names, name)
+            end
+        end
+    end
+    table.sort(instance_names)
+    return instance_names
+end
+
+-- }}} Helpers
+
+-- {{{ Cluster management
+
+--- Execute for server in the cluster.
+--
+-- @func f Function to execute with a server as the first param.
+function Cluster:each(f)
+    fun.iter(self._servers):each(function(iserver)
+        f(iserver)
+    end)
+end
+
+--- Get cluster size.
+--
+-- @return number.
+function Cluster:size()
+    return #self._servers
+end
+
+--- Start all the instances.
+--
+-- @tab[opt] opts Cluster startup options.
+-- @bool[opt] opts.wait_until_ready Wait until servers are ready
+--   (default: false).
+function Cluster:start(opts)
+    self:each(function(iserver)
+        iserver:start({wait_until_ready = false})
+    end)
+
+    -- wait_until_ready is true by default.
+    local wait_until_ready = true
+    if opts ~= nil and opts.wait_until_ready ~= nil then
+        wait_until_ready = opts.wait_until_ready
+    end
+
+    if wait_until_ready then
+        self:each(function(iserver)
+            iserver:wait_until_ready()
+        end)
+    end
+
+    -- wait_until_running is equal to wait_until_ready by default.
+    local wait_until_running = wait_until_ready
+    if opts ~= nil and opts.wait_until_running ~= nil then
+        wait_until_running = opts.wait_until_running
+    end
+
+    if wait_until_running then
+        self:each(function(iserver)
+            helpers.retrying({timeout = 60}, function()
+                assertions.assert_equals(iserver:eval('return box.info.status'),
+                                         'running')
+            end)
+
+        end)
+    end
+end
+
+--- Start the given instance.
+--
+-- @string instance_name Instance name.
+function Cluster:start_instance(instance_name)
+    local iserver = self._server_map[instance_name]
+    assert(iserver ~= nil)
+    iserver:start()
+end
+
+--- Stop the whole cluster.
+function Cluster:stop()
+    for _, iserver in ipairs(self._servers or {}) do
+        iserver:stop()
+    end
+end
+
+--- Drop the cluster's servers.
+function Cluster:drop()
+    for _, iserver in ipairs(self._servers or {}) do
+        iserver:drop()
+    end
+    self._servers = nil
+    self._server_map = nil
+end
+
+--- Sync the cluster object with the new config.
+--
+-- It performs the following actions.
+--
+-- * Write the new config into the config file.
+-- * Update the internal list of instances.
+--
+-- @tab config New config.
+function Cluster:sync(config)
+    assert(type(config) == 'table')
+
+    local instance_names = instance_names_from_config(config)
+
+    treegen.write_file(self._dir, self._config_file_rel, yaml.encode(config))
+
+    for i, name in ipairs(instance_names) do
+        if self._server_map[name] == nil then
+            local iserver = server:new(fun.chain(self._server_opts, {
+                alias = name,
+            }):tomap())
+            table.insert(self._servers, i, iserver)
+            self._server_map[name] = iserver
+        end
+    end
+
+end
+
+--- Reload configuration on all the instances.
+--
+-- @tab[opt] config New config.
+function Cluster:reload(config)
+    assert(config == nil or type(config) == 'table')
+
+    -- Rewrite the configuration file if a new config is provided.
+    if config ~= nil then
+        treegen.write_file(self._dir, self._config_file_rel,
+                           yaml.encode(config))
+    end
+
+    -- Reload config on all the instances.
+    self:each(function(iserver)
+        -- Assume that all the instances are started.
+        --
+        -- This requirement may be relaxed if needed, it is just
+        -- for simplicity.
+        assert(iserver.process ~= nil)
+
+        iserver:exec(function()
+            local cfg = require('config')
+
+            cfg:reload()
+        end)
+    end)
+end
+
+--- Create a new Tarantool cluster.
+--
+-- @tab config Cluster configuration.
+-- @tab[opt] server_opts Extra options passed to server:new().
+-- @tab[opt] opts Cluster options.
+-- @string[opt] opts.dir Specific directory for the cluster.
+-- @return table
+function Cluster:new(config, server_opts, opts)
+    local g = cluster._group
+
+    assert(type(config) == 'table')
+    assert(config._config == nil, "Please provide cbuilder:new():config()")
+    assert(g._cluster == nil)
+
+    -- Prepare a temporary directory and write a configuration
+    -- file.
+    local dir = opts and opts.dir or treegen.prepare_directory({}, {})
+    local config_file_rel = 'config.yaml'
+    local config_file = treegen.write_file(dir, config_file_rel,
+                                           yaml.encode(config))
+
+    -- Collect names of all the instances defined in the config
+    -- in the alphabetical order.
+    local instance_names = instance_names_from_config(config)
+
+    assert(next(instance_names) ~= nil, 'No instances in the supplied config')
+
+    -- Generate luatest server options.
+    server_opts = fun.chain({
+        config_file = config_file,
+        chdir = dir,
+        net_box_credentials = {
+            user = 'client',
+            password = 'secret',
+        },
+    }, server_opts or {}):tomap()
+
+    -- Create luatest server objects.
+    local servers = {}
+    local server_map = {}
+    for _, name in ipairs(instance_names) do
+        local iserver = server:new(fun.chain(server_opts, {
+            alias = name,
+        }):tomap())
+        table.insert(servers, iserver)
+        server_map[name] = iserver
+    end
+
+    -- Store a cluster object in 'g'.
+    self._servers = servers
+    self._server_map = server_map
+    self._dir = dir
+    self._config_file_rel = config_file_rel
+    self._server_opts = server_opts
+
+    g._cluster = self
+
+    return self
+end
+
+-- }}} Replicaset management
+
+-- {{{ Replicaset that can't start
+
+--- Ensure cluster startup error
+--
+-- Starts a all instance of a cluster from the given config and
+-- ensure that all the instances fails to start and reports the
+-- given error message.
+--
+-- @tab config Cluster configuration.
+-- @string exp_err Expected error message.
+function Cluster:startup_error(config, exp_err)
+    -- Stub for the linter, since self is unused though
+    -- we need to be consistent with Cluster:new()
+    assert(self)
+    assert(type(config) == 'table')
+    assert(config._config == nil, "Please provide cbuilder:new():config()")
+    -- Prepare a temporary directory and write a configuration
+    -- file.
+    local dir = treegen.prepare_directory({}, {})
+    local config_file_rel = 'config.yaml'
+    local config_file = treegen.write_file(dir, config_file_rel,
+                                           yaml.encode(config))
+
+    -- Collect names of all the instances defined in the config
+    -- in the alphabetical order.
+    local instance_names = instance_names_from_config(config)
+
+    for _, name in ipairs(instance_names) do
+        local env = {}
+        local args = {'--name', name, '--config', config_file}
+        local opts = {nojson = true, stderr = true}
+        local res = justrun.tarantool(dir, env, args, opts)
+
+        assertions.assert_equals(res.exit_code, 1)
+        assertions.assert_str_contains(res.stderr, exp_err)
+    end
+end
+
+-- }}} Replicaset that can't start
+
+hooks.before_all_preloaded(init)
+hooks.after_each_preloaded(drop)
+hooks.after_all_preloaded(clean)
+
+return Cluster

luatest/init.lua

@@ -48,6 +48,11 @@ luatest.justrun = require('luatest.justrun')
 -- @see luatest.cbuilder
 luatest.cbuilder = require('luatest.cbuilder')
 
+--- Tarantool cluster management utils.
+--
+-- @see luatest.cluster
+luatest.cluster = require('luatest.cluster')
+
 --- Add before suite hook.
 --
 -- @function before_suite