From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from localhost (localhost [127.0.0.1]) by turing.freelists.org (Avenir Technologies Mail Multiplex) with ESMTP id 9458E28702 for ; Wed, 1 Aug 2018 13:44:09 -0400 (EDT) Received: from turing.freelists.org ([127.0.0.1]) by localhost (turing.freelists.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id HFHISZJ2CstT for ; Wed, 1 Aug 2018 13:44:09 -0400 (EDT) Received: from smtp61.i.mail.ru (smtp61.i.mail.ru [217.69.128.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by turing.freelists.org (Avenir Technologies Mail Multiplex) with ESMTPS id 443E828297 for ; Wed, 1 Aug 2018 13:44:09 -0400 (EDT) Subject: [tarantool-patches] Re: [PATCH 1/4] Fix races related to object outdating References: <18f2ede05fa4a77bf0bd2abb64c25df0e3c574d6.1532940401.git.avkhatskevich@tarantool.org> <4a8e9e20-561d-6896-ea8c-8517add2bc50@tarantool.org> <1eeb6917-0153-919d-de56-c21052ea42f9@tarantool.org> <39dccfbe-8d6a-ffe7-b841-efa0c5352697@tarantool.org> From: Alex Khatskevich Message-ID: Date: Wed, 1 Aug 2018 20:44:00 +0300 MIME-Version: 1.0 In-Reply-To: <39dccfbe-8d6a-ffe7-b841-efa0c5352697@tarantool.org> Content-Type: text/plain; charset="utf-8"; format="flowed" Content-Transfer-Encoding: 8bit Content-Language: en-US Sender: tarantool-patches-bounce@freelists.org Errors-to: tarantool-patches-bounce@freelists.org Reply-To: tarantool-patches@freelists.org List-help: List-unsubscribe: List-software: Ecartis version 1.0.0 List-Id: tarantool-patches List-subscribe: List-owner: List-post: List-archive: To: Vladislav Shpilevoy , tarantool-patches@freelists.org On 01.08.2018 15:36, Vladislav Shpilevoy wrote: > Hi! Thanks for the patch! See 2 comments below. > >> diff --git a/vshard/router/init.lua b/vshard/router/init.lua >> index 142ddb6..1a0ed2f 100644 >> --- a/vshard/router/init.lua >> +++ b/vshard/router/init.lua >> @@ -88,15 +94,18 @@ local function bucket_discovery(bucket_id) >>      log.verbose("Discovering bucket %d", bucket_id) >>      local last_err = nil >>      local unreachable_uuid = nil >> -    for uuid, replicaset in pairs(M.replicasets) do >> -        local _, err = >> -            replicaset:callrw('vshard.storage.bucket_stat', >> {bucket_id}) >> -        if err == nil then >> -            bucket_set(bucket_id, replicaset) >> -            return replicaset >> -        elseif err.code ~= lerror.code.WRONG_BUCKET then >> -            last_err = err >> -            unreachable_uuid = uuid >> +    for uuid, _ in pairs(M.replicasets) do >> +        -- Handle reload/reconfigure. >> +        replicaset = M.replicasets[uuid] > > 1. Please, explain, how is it possible, that before this line > M.replicasets[uuid] can become nil. You iterate here over > M.replicasets and on the previous line in '_' you have > stored replicaset. How can here 'replicaset' differ from '_'? > > It has nothing in common with 'reload/reconfigure' case since > you always iterate over M.replicasets - the most actual > list of replicasets. Maybe you thought that pairs() stores > its first argument into a temporary variable but looks like > it is not. I checked it with a simple test: > >     a = {} >     a.objs = {1, 2, 3, 4, 5} >     for k, v in pairs(a.objs) do >         print(a.objs[k]) >         if k == 2 then >             a.objs = {6, 7, 8, 9, 10} >         end >     end > >     Output: >     1 >     2 >     8 >     9 >     10 >     --- >     ... Thanks. For some reason I was sure that pairs caches the table. Fixed. >> +        if replicaset then >> +            local _, err = >> +                replicaset:callrw('vshard.storage.bucket_stat', >> {bucket_id}) >> +            if err == nil then >> +                return bucket_set(bucket_id, replicaset.uuid) >> +            elseif err.code ~= lerror.code.WRONG_BUCKET then >> +                last_err = err >> +                unreachable_uuid = uuid >> +            end >>          end >>      end >>      local err = nil >> @@ -513,27 +522,28 @@ local function router_cfg(cfg) >>      end >>      box.cfg(box_cfg) >>      log.info("Box has been configured") >> -    M.connection_outdate_delay = cfg.connection_outdate_delay >> -    M.total_bucket_count = total_bucket_count >> -    M.collect_lua_garbage = collect_lua_garbage >> -    M.current_cfg = new_cfg >>      -- Move connections from an old configuration to a new one. >>      -- It must be done with no yields to prevent usage both of not >>      -- fully moved old replicasets, and not fully built new ones. >> -    lreplicaset.rebind_replicasets(new_replicasets, M.replicasets, >> -                                   M.connection_outdate_delay) >> -    M.replicasets = new_replicasets >> +    lreplicaset.rebind_replicasets(new_replicasets, M.replicasets) >>      -- Now the new replicasets are fully built. Can establish >>      -- connections and yield. >>      for _, replicaset in pairs(new_replicasets) do >>          replicaset:connect_all() >>      end >> +    lreplicaset.wait_masters_connect(new_replicasets) >> +    lreplicaset.outdate_replicasets(M.replicasets, >> cfg.connection_outdate_delay) >> +    M.connection_outdate_delay = cfg.connection_outdate_delay >> +    M.total_bucket_count = total_bucket_count >> +    M.collect_lua_garbage = collect_lua_garbage >> +    M.current_cfg = cfg >> +    M.replicasets = new_replicasets >>      -- Update existing route map in-place. >> -    for bucket, rs in pairs(M.route_map) do >> +    local old_route_map = M.route_map >> +    M.route_map = {} >> +    for bucket, rs in pairs(old_route_map) do >>          M.route_map[bucket] = M.replicasets[rs.uuid] > > 2. Why do you need to save old_route_map into a > separate variable? You can update M.route_map in place > like it was done before. It is not? You fill the new > route_map with exactly the same keys (maybe with different > values, but it does not affect 'for' iteration). Moreover, > when you create a new route_map instead of resetting the > old, you double the memory. For huge bucket count it can > be noticeable. Yes there is no point in that change. Fixed. >>      end >> - >> -    lreplicaset.wait_masters_connect(new_replicasets) >>      if M.failover_fiber == nil then >>          lfiber.create(util.reloadable_fiber_f, M, 'failover_f', >> 'Failover') >>      end