test: retry cluster init if unhealthy

Sometimes cluster fails to bootstrap in tests. The reasons are yet
unknown and likely unrelated to crud or maybe even crud tests setup.

After this patch, in case cluster preparation had failed for a test,
we retry to create a cluster up t three times.

Part of #432

test/helper.lua

@@ -902,30 +902,63 @@ function helpers.start_tarantool3_cluster(g, cfg)
 end
 
 function helpers.start_cluster(g, cartridge_cfg, vshard_cfg, tarantool3_cluster_cfg, opts)
-    checks('table', '?table', '?table', '?table', {wait_crud_is_ready = '?boolean'})
+    checks('table', '?table', '?table', '?table', {
+        wait_crud_is_ready = '?boolean',
+        backend = '?string',
+        retries = '?number',
+    })
 
     opts = opts or {}
+
     if opts.wait_crud_is_ready == nil then
         opts.wait_crud_is_ready = true
     end
 
-    if g.params.backend == helpers.backend.CARTRIDGE then
-        helpers.skip_cartridge_unsupported()
-
-        helpers.start_cartridge_cluster(g, cartridge_cfg)
-    elseif g.params.backend == helpers.backend.VSHARD then
-        helpers.start_vshard_cluster(g, vshard_cfg)
-    elseif g.params.backend == helpers.backend.CONFIG then
-        helpers.skip_if_tarantool3_crud_roles_unsupported()
+    if opts.backend == nil then
+        opts.backend = g.params.backend
+    end
+    assert(opts.backend ~= nil, 'Please, provide backend')
 
-        helpers.start_tarantool3_cluster(g, tarantool3_cluster_cfg)
+    local DEFAULT_RETRIES = 3
+    if opts.retries == nil then
+        opts.retries = DEFAULT_RETRIES
     end
 
-    g.router = g.cluster:server('router')
-    assert(g.router ~= nil, 'router found')
+    local current_attempt = 0
+    while true do
+        current_attempt = current_attempt + 1
+
+        if opts.backend == helpers.backend.CARTRIDGE then
+            helpers.skip_cartridge_unsupported()
+
+            helpers.start_cartridge_cluster(g, cartridge_cfg)
+        elseif opts.backend == helpers.backend.VSHARD then
+            helpers.start_vshard_cluster(g, vshard_cfg)
+        elseif opts.backend == helpers.backend.CONFIG then
+            helpers.skip_if_tarantool3_crud_roles_unsupported()
 
-    if opts.wait_crud_is_ready then
-        helpers.wait_crud_is_ready_on_cluster(g)
+            helpers.start_tarantool3_cluster(g, tarantool3_cluster_cfg)
+        end
+
+        g.router = g.cluster:server('router')
+        assert(g.router ~= nil, 'router found')
+
+        local ok, err = false, nil -- luacheck: ignore
+        if opts.wait_crud_is_ready then
+            ok, err = pcall(helpers.wait_crud_is_ready_on_cluster, g, {backend = opts.backend})
+        else
+            ok = true
+        end
+
+        if ok then
+            break
+        end
+
+        helpers.stop_cluster(g.cluster, opts.backend)
+
+        if current_attempt == opts.retries then
+            error(err)
+        end
     end
 end
 

test/integration/role_test.lua

@@ -13,10 +13,9 @@ end)
 g.before_each(function(cg)
     -- Tests are rather dangerous and may break the cluster,
     -- so it's safer to restart for each case.
-    helpers.start_tarantool3_cluster(cg, cg.template_cfg)
-    cg.router = cg.cluster:server('router')
-
-    helpers.wait_crud_is_ready_on_cluster(cg, {backend = helpers.backend.CONFIG})
+    helpers.start_cluster(cg, nil, nil, cg.template_cfg, {
+        backend = helpers.backend.CONFIG,
+    })
 end)
 
 g.after_each(function(cg)

test/unit/not_initialized_test.lua

@@ -83,7 +83,7 @@ pgroup.before_all(function(g)
         cartridge_cfg_template,
         vshard_cfg_template,
         tarantool3_cluster_cfg_template,
-        {wait_crud_is_ready = false}
+        {wait_crud_is_ready = false, retries = 1}
     )
 
     g.router = g.cluster:server('router')