From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp29.i.mail.ru (smtp29.i.mail.ru [94.100.177.89]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dev.tarantool.org (Postfix) with ESMTPS id 52995469710 for ; Fri, 20 Nov 2020 13:33:58 +0300 (MSK) References: <20201119194100.840495-1-gorcunov@gmail.com> <20201119194100.840495-4-gorcunov@gmail.com> From: Serge Petrenko Message-ID: <1a8fa5cf-ad2a-26f3-3a9d-95367c014cbf@tarantool.org> Date: Fri, 20 Nov 2020 13:32:42 +0300 MIME-Version: 1.0 In-Reply-To: <20201119194100.840495-4-gorcunov@gmail.com> Content-Type: text/plain; charset="utf-8"; format="flowed" Content-Transfer-Encoding: 8bit Content-Language: en-GB Subject: Re: [Tarantool-patches] [RFC 3/4] cfg: prepare symbolic evaluation of replication_synchro_quorum List-Id: Tarantool development patches List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Cyrill Gorcunov , tml Cc: Vladislav Shpilevoy 19.11.2020 22:40, Cyrill Gorcunov пишет: > Prepare scaffolds to evaluate replication_synchro_quorum, > since we don't yet update the undeneath engines we accept > and verify the formulas but refuse to proceed. > > In next patch we will support dynamic evaluation of > the quorum number. > > Part-of #5446 Hi! Thanks for the patch! Please find my comments below. > > Signed-off-by: Cyrill Gorcunov > --- > src/box/box.cc | 82 +++++++++++++++++++++++++++++++++++++++- > src/box/box.h | 1 + > src/box/lua/load_cfg.lua | 3 +- > 3 files changed, 83 insertions(+), 3 deletions(-) > > diff --git a/src/box/box.cc b/src/box/box.cc > index 5fcf28cb3..5f7ddfa99 100644 > --- a/src/box/box.cc > +++ b/src/box/box.cc > @@ -562,10 +562,90 @@ box_check_replication_sync_lag(void) > return lag; > } > > +/** > + * Evaluate replicaion syncro quorum number from a formula. > + */ > +int > +eval_replication_synchro_quorum(int nr_replicas) > +{ > + const char fmt[] = > + "local f, err = loadstring(\"return (%s)\")\n" > + "if not f then return 'failed to load \"%s\"' end\n" > + "setfenv(f, { n = %d })\n" > + "local ok, res = pcall(f)\n" > + "if not ok then return res end\n" > + "return math.floor(res)\n"; > + char buf[512]; > + int value = -1; > + > + errno = 0; > + > + const char *expr = cfg_gets("replication_synchro_quorum"); > + size_t ret = snprintf(buf, sizeof(buf), fmt, expr, > + expr, nr_replicas); > + if (ret >= sizeof(buf)) { > + errno = EINVAL; > + diag_set(ClientError, ER_CFG, > + "replication_synchro_quorum", > + "the expression is too big"); > + return -1; > + } > + > + luaL_loadstring(tarantool_L, buf); > + lua_call(tarantool_L, 0, 1); > + > + if (lua_isnumber(tarantool_L, -1)) { > + value = (int)lua_tonumber(tarantool_L, -1); > + } else { > + assert(lua_isstring(tarantool_L, -1)); > + errno = EINVAL; > + diag_set(ClientError, ER_CFG, > + "replication_synchro_quorum", > + lua_tostring(tarantool_L, -1)); > + } > + lua_pop(tarantool_L, 1); > + return value; > +} Better make  the function return -1 on an error, and when the function evaluates to something negative, log the eval result and return 1. This way you won't need errno. > + > static int > box_check_replication_synchro_quorum(void) > { > - int quorum = cfg_geti("replication_synchro_quorum"); > + int quorum = 0; > + > + if (!cfg_isnumber("replication_synchro_quorum")) { > + /* > + * When validating a formula it must return a > + * positive value for a single node and maximum > + * possible replicas because the quorum will be > + * evaluated on each new replica registration, > + * starting from a single node. > + */ > + int v[] = {1, VCLOCK_MAX-1}; > + for (size_t i = 0; i < lengthof(v); i++) { > + quorum = eval_replication_synchro_quorum(v[i]); > + if (quorum < 0 && errno == EINVAL) > + return -1; > + } You should either check every possible value, from 1 to VCLOCK_MAX - 1, to make sure, say, that no division by zero is involved for some input. or check a single value, say, 1, or 2 or whatever, to make sure that the expression in replication_synchro_quorum is  at least valid Lua code. Why check only min and max inputs? > + > + /* > + * Once syntax is valid we should pass the real > + * default value from replication module itself > + * to evaluate the actual value to use. > + */ > + int value = replication_synchro_quorum; > + quorum = eval_replication_synchro_quorum(value); > + /* > + * FIXME: Until we get full support. > + */ > + diag_set(ClientError, ER_CFG, > + "replication_synchro_quorum", > + "symbolic evaluation is not yet supported"); > + diag_log(); > + quorum = -1; > + } else { > + quorum = cfg_geti("replication_synchro_quorum"); > + } > + > if (quorum <= 0 || quorum >= VCLOCK_MAX) { > diag_set(ClientError, ER_CFG, "replication_synchro_quorum", > "the value must be greater than zero and less than " > diff --git a/src/box/box.h b/src/box/box.h > index b47a220b7..8f438faab 100644 > --- a/src/box/box.h > +++ b/src/box/box.h > @@ -252,6 +252,7 @@ void box_set_replication_connect_timeout(void); > void box_set_replication_connect_quorum(void); > void box_set_replication_sync_lag(void); > int box_set_replication_synchro_quorum(void); > +int eval_replication_synchro_quorum(int nr_replicas); > int box_set_replication_synchro_timeout(void); > void box_set_replication_sync_timeout(void); > void box_set_replication_skip_conflict(void); > diff --git a/src/box/lua/load_cfg.lua b/src/box/lua/load_cfg.lua > index 76e2e92c2..26725e08d 100644 > --- a/src/box/lua/load_cfg.lua > +++ b/src/box/lua/load_cfg.lua > @@ -172,7 +172,7 @@ local template_cfg = { > replication_timeout = 'number', > replication_sync_lag = 'number', > replication_sync_timeout = 'number', > - replication_synchro_quorum = 'number', > + replication_synchro_quorum = 'string, number', > replication_synchro_timeout = 'number', > replication_connect_timeout = 'number', > replication_connect_quorum = 'number', > @@ -368,7 +368,6 @@ local dynamic_cfg_skip_at_load = { > replication_connect_quorum = true, > replication_sync_lag = true, > replication_sync_timeout = true, > - replication_synchro_quorum = true, You shouldn't remove replication_synchro_quorum from here. This table  lists the options which are set directly from `box_cfg` in specific order. I.e. not lua calls  box_cfg_set_..., but box_cfg() itself does. But only on the first box.cfg call. > replication_synchro_timeout = true, > replication_skip_conflict = true, > replication_anon = true, -- Serge Petrenko