experimental: introduce filter()

This patch introduces the filter() function in the experimental.connpool
module. The function takes options containing some constraints as the
only argument and returns an array of instance names that satisfy those
constraints.

Part of #9842

NO_DOC=will be added later

changelogs/unreleased/gh-9842-rpc-for-roles.md

@@ -2,3 +2,5 @@
 
 * Introduced the `experimental.connpool` module and the
   `connect()` function of this module (gh-9842).
+* Introduced the `filter()` function in the `experimental.connpool`
+  module (gh-9842).

src/box/lua/experimental/connpool.lua

@@ -55,6 +55,64 @@ local function connect(instance_name, opts)
     return conn
 end
 
+local function is_roles_match(expected_roles, present_roles)
+    if expected_roles == nil or next(expected_roles) == nil then
+        return true
+    end
+    if present_roles == nil or next(present_roles) == nil then
+        return false
+    end
+
+    local roles = {}
+    for _, present_role_name in pairs(present_roles) do
+        roles[present_role_name] = true
+    end
+    for _, expected_role_name in pairs(expected_roles) do
+        if roles[expected_role_name] == nil then
+            return false
+        end
+    end
+    return true
+end
+
+local function is_labels_match(expected_labels, present_labels)
+    if expected_labels == nil or next(expected_labels) == nil then
+        return true
+    end
+    if present_labels == nil or next(present_labels) == nil then
+        return false
+    end
+
+    for label, value in pairs(expected_labels) do
+        if present_labels[label] ~= value then
+            return false
+        end
+    end
+    return true
+end
+
+local function is_candidate_match(instance_name, opts)
+    assert(opts ~= nil and type(opts) == 'table')
+    local get_opts = {instance = instance_name}
+    return is_roles_match(opts.roles, config:get('roles', get_opts)) and
+           is_labels_match(opts.labels, config:get('labels', get_opts))
+end
+
+local function filter(opts)
+    checks({
+        labels = '?table',
+        roles = '?table',
+    })
+    local candidates = {}
+    for instance_name in pairs(config:instances()) do
+        if is_candidate_match(instance_name, opts or {}) then
+            table.insert(candidates, instance_name)
+        end
+    end
+    return candidates
+end
+
 return {
     connect = connect,
+    filter = filter,
 }

test/config-luatest/rpc_test.lua

@@ -97,3 +97,110 @@ g.test_connect = function(g)
     g.server_3:exec(check_conn)
     g.server_4:exec(check_conn)
 end
+
+g.test_filter = 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:
+                database:
+                  mode: rw
+                roles: [r1, r2]
+                labels:
+                  l1: 'one'
+                  l2: 'two'
+              instance-002:
+                labels:
+                  l1: 'one'
+          replicaset-002:
+            instances:
+              instance-003:
+                database:
+                  mode: rw
+                roles: [r1, r2]
+              instance-004:
+                labels:
+                  l1: 'one_one'
+                  l3: 'three'
+                roles: [r1]
+    ]]
+    treegen.write_script(dir, 'config.yaml', config)
+
+    local role = string.dump(function()
+        return {
+            stop = function() end,
+            apply = function() end,
+            validate = function() end,
+        }
+    end)
+    treegen.write_script(dir, 'r1.lua', role)
+    treegen.write_script(dir, 'r2.lua', role)
+
+    local opts = {
+        env = {LUA_PATH = os.environ()['LUA_PATH']},
+        config_file = 'config.yaml',
+        chdir = dir,
+    }
+    g.server_1 = server:new(fun.chain(opts, {alias = 'instance-001'}):tomap())
+    g.server_2 = server:new(fun.chain(opts, {alias = 'instance-002'}):tomap())
+    g.server_3 = server:new(fun.chain(opts, {alias = 'instance-003'}):tomap())
+    g.server_4 = server:new(fun.chain(opts, {alias = 'instance-004'}):tomap())
+
+    g.server_1:start({wait_until_ready = false})
+    g.server_2:start({wait_until_ready = false})
+    g.server_3:start({wait_until_ready = false})
+    g.server_4:start({wait_until_ready = false})
+
+    g.server_1:wait_until_ready()
+    g.server_2:wait_until_ready()
+    g.server_3:wait_until_ready()
+    g.server_4:wait_until_ready()
+
+    local function check()
+        local connpool = require('experimental.connpool')
+        local exp = {"instance-001", "instance-004", "instance-003"}
+        local opts = {roles = {'r1'}}
+        t.assert_items_equals(connpool.filter(opts), exp)
+
+        exp = {"instance-001", "instance-003"}
+        opts = {roles = {'r1', 'r2'}}
+        t.assert_items_equals(connpool.filter(opts), exp)
+
+        exp = {"instance-001", "instance-002"}
+        opts = {labels = {l1 = 'one'}}
+        t.assert_items_equals(connpool.filter(opts), exp)
+
+        exp = {"instance-001"}
+        opts = {labels = {l1 = 'one', l2 = 'two'}}
+        t.assert_items_equals(connpool.filter(opts), exp)
+
+        exp = {"instance-004"}
+        opts = {labels = {l1 = 'one_one'}, roles = {'r1'}}
+        t.assert_items_equals(connpool.filter(opts), exp)
+
+        exp = {}
+        opts = {labels = {l1 = 'one_one', l2 = 'two'}, roles = {'r1'}}
+        t.assert_items_equals(connpool.filter(opts), exp)
+
+        exp = {"instance-001", "instance-002", "instance-003", "instance-004"}
+        t.assert_items_equals(connpool.filter(), exp)
+    end
+
+    g.server_1:exec(check)
+    g.server_2:exec(check)
+    g.server_3:exec(check)
+    g.server_4:exec(check)
+end