From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from [87.239.111.99] (localhost [127.0.0.1]) by dev.tarantool.org (Postfix) with ESMTP id 15C8A6F867; Tue, 1 Feb 2022 00:57:02 +0300 (MSK) DKIM-Filter: OpenDKIM Filter v2.11.0 dev.tarantool.org 15C8A6F867 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=tarantool.org; s=dev; t=1643666222; bh=E7Yfa+iOmgx8yYQdZ7VMGgZbb0Agi205VuUpLK463EY=; h=To:Date:In-Reply-To:References:Subject:List-Id:List-Unsubscribe: List-Archive:List-Post:List-Help:List-Subscribe:From:Reply-To:Cc: From; b=D+rCWwyEdBGvAGGktDK84X3PnSUvYTA0C60Ht3SJYwoFQBMZLTRSEQRr2Xtq+X7xH gnN1/66vNGFevBTktwWAWG75FcZunaejZPBHI410PoRK6qENTyeWauEgwRraOOE1h0 3ETRLRd10noI0sWr7Y4IbsFJ96P2Xou1elB1IGO8= Received: from mail-lf1-f54.google.com (mail-lf1-f54.google.com [209.85.167.54]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by dev.tarantool.org (Postfix) with ESMTPS id BFA236F868 for ; Tue, 1 Feb 2022 00:56:22 +0300 (MSK) DKIM-Filter: OpenDKIM Filter v2.11.0 dev.tarantool.org BFA236F868 Received: by mail-lf1-f54.google.com with SMTP id p27so29812129lfa.1 for ; Mon, 31 Jan 2022 13:56:22 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=ZsNIqK8LokQxv8/SC1iYCnm5UdBklVbisTmXAoXL+hs=; b=UeIDEDJQAMFT4g1TE/loEl+N4gC51zvebB6kQbf6816cdo8mTMhZ9pLeYYSBviLlMq SYHwKnt1lc+ffMCysOj0x3DGbpqMdPYkzabW9CB8CbpjFxPd1+UBeMc+AdpWxTttnAXP DaLLKcUj2BnLgPVtYHwDHA2et6vKRmitfmIUVqcHyyoEei06sFetyV+VkizCvFrTwUgv znLiPpx1qLciUApWkVX+sTUMJO+lNv0auZ10XCoNr78zqnWKkrFwo7OZi6RcPIrWT9NP ks+/G+T0RNn8wR/Cgq1hsP81ZxPCoQjoX4NfoLGKHL5M5nLODbNni6K4CzsBXGA6+013 GQ2Q== X-Gm-Message-State: AOAM531tLriEdGM6LWQvLWJTxzyY5NZuByxHmAucS03tjbj8jvbQ/Jdx 9XUtxEs6Q0jLApL2TmYtIY8gbmfiEAI= X-Google-Smtp-Source: ABdhPJynVu8zkrTNFTXDpMlWJlJLs/9qERiWNpzTgBck1KULf6zcb0PaesyoyPP4tc1iqRGiNeCgtQ== X-Received: by 2002:a05:6512:1151:: with SMTP id m17mr16441416lfg.610.1643666181661; Mon, 31 Jan 2022 13:56:21 -0800 (PST) Received: from grain.localdomain ([5.18.251.97]) by smtp.gmail.com with ESMTPSA id f15sm2037944lfk.198.2022.01.31.13.56.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 31 Jan 2022 13:56:20 -0800 (PST) Received: by grain.localdomain (Postfix, from userid 1000) id 26C9D5A0022; Tue, 1 Feb 2022 00:55:57 +0300 (MSK) To: tml Date: Tue, 1 Feb 2022 00:55:53 +0300 Message-Id: <20220131215554.1367429-3-gorcunov@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220131215554.1367429-1-gorcunov@gmail.com> References: <20220131215554.1367429-1-gorcunov@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Subject: [Tarantool-patches] [RFC v29 2/3] qsync: order access to the limbo terms X-BeenThere: tarantool-patches@dev.tarantool.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: Tarantool development patches List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , From: Cyrill Gorcunov via Tarantool-patches Reply-To: Cyrill Gorcunov Cc: Vladislav Shpilevoy Errors-To: tarantool-patches-bounces@dev.tarantool.org Sender: "Tarantool-patches" Limbo terms tracking is shared between appliers and when one of appliers is waiting for write to complete inside journal_write() routine, an other may need to access read term value to figure out if promote request is valid to apply. Due to cooperative multitasking access to the terms is not consistent so we need to be sure that other fibers read up to date terms (ie written to the WAL). For this sake we use a latching mechanism, when one fiber takes a lock for updating other readers are waiting until the operation is complete. For example here is a call graph of two appliers applier 1 --------- applier_apply_tx (promote term = 3 current max term = 2) applier_synchro_filter_tx apply_synchro_row journal_write (sleeping) at this moment another applier comes in with obsolete data and term 2 applier 2 --------- applier_apply_tx (term 2) applier_synchro_filter_tx txn_limbo_is_replica_outdated -> false journal_write (sleep) applier 1 --------- journal wakes up apply_synchro_row_cb set max term to 3 So the applier 2 didn't notice that term 3 is already seen and wrote obsolete data. With locking the applier 2 will wait until applier 1 has finished its write. We introduce the following helpers: 1) txn_limbo_begin: which takes a lock 2) txn_limbo_commit and txn_limbo_rollback which simply release the lock but have different names for better semantics 3) txn_limbo_process is a general function which uses x_begin and x_commit helper internally 4) txn_limbo_apply to do a real job over processing the request, it implies that txn_limbo_begin been called Testing such in-flight condition won't be easy so we introduce "box.info.synchro.queue.latched" field to report if limbo is currently latched and processing a sync request. @TarantoolBot document Title: synchronous replication changes `box.info.synchro.queue` gets a new `latched` field. It is set to `true` when there is a synchronous transaction is processing but not yet complete. Thus any other incoming synchronous transactions will be delayed until active one is finished. Part-of #6036 Signed-off-by: Cyrill Gorcunov --- src/box/applier.cc | 6 +++++- src/box/box.cc | 8 +++++-- src/box/lua/info.c | 4 +++- src/box/txn_limbo.c | 18 ++++++++++++++-- src/box/txn_limbo.h | 52 ++++++++++++++++++++++++++++++++++++++++----- 5 files changed, 77 insertions(+), 11 deletions(-) diff --git a/src/box/applier.cc b/src/box/applier.cc index 11a2a3adb..f3d251a4d 100644 --- a/src/box/applier.cc +++ b/src/box/applier.cc @@ -964,7 +964,7 @@ apply_synchro_req_cb(struct journal_entry *entry) applier_rollback_by_wal_io(entry->res); } else { replica_txn_wal_write_cb(synchro_entry->rcb); - txn_limbo_process(&txn_limbo, synchro_entry->req); + txn_limbo_apply(&txn_limbo, synchro_entry->req); trigger_run(&replicaset.applier.on_wal_write, NULL); } fiber_wakeup(synchro_entry->owner); @@ -1009,14 +1009,18 @@ apply_synchro_req(uint32_t replica_id, struct xrow_header *row, struct synchro_r * before trying to commit. But that requires extra steps from the * transactions side, including the async ones. */ + txn_limbo_begin(&txn_limbo); if (journal_write(&entry.base) != 0) goto err; if (entry.base.res < 0) { diag_set_journal_res(entry.base.res); goto err; } + txn_limbo_commit(&txn_limbo); return 0; + err: + txn_limbo_rollback(&txn_limbo); diag_log(); return -1; } diff --git a/src/box/box.cc b/src/box/box.cc index 450fa2357..cc7dcedde 100644 --- a/src/box/box.cc +++ b/src/box/box.cc @@ -1780,6 +1780,7 @@ box_issue_promote(uint32_t prev_leader_id, int64_t promote_lsn) struct raft *raft = box_raft(); assert(raft->volatile_term == raft->term); assert(promote_lsn >= 0); + txn_limbo_begin(&txn_limbo); txn_limbo_write_promote(&txn_limbo, promote_lsn, raft->term); struct synchro_request req = { @@ -1789,7 +1790,8 @@ box_issue_promote(uint32_t prev_leader_id, int64_t promote_lsn) .lsn = promote_lsn, .term = raft->term, }; - txn_limbo_process(&txn_limbo, &req); + txn_limbo_apply(&txn_limbo, &req); + txn_limbo_commit(&txn_limbo); assert(txn_limbo_is_empty(&txn_limbo)); } @@ -1802,6 +1804,7 @@ box_issue_demote(uint32_t prev_leader_id, int64_t promote_lsn) { assert(box_raft()->volatile_term == box_raft()->term); assert(promote_lsn >= 0); + txn_limbo_begin(&txn_limbo); txn_limbo_write_demote(&txn_limbo, promote_lsn, box_raft()->term); struct synchro_request req = { @@ -1811,7 +1814,8 @@ box_issue_demote(uint32_t prev_leader_id, int64_t promote_lsn) .lsn = promote_lsn, .term = box_raft()->term, }; - txn_limbo_process(&txn_limbo, &req); + txn_limbo_apply(&txn_limbo, &req); + txn_limbo_commit(&txn_limbo); assert(txn_limbo_is_empty(&txn_limbo)); } diff --git a/src/box/lua/info.c b/src/box/lua/info.c index 8e02f6594..f0a9e5339 100644 --- a/src/box/lua/info.c +++ b/src/box/lua/info.c @@ -637,11 +637,13 @@ lbox_info_synchro(struct lua_State *L) /* Queue information. */ struct txn_limbo *queue = &txn_limbo; - lua_createtable(L, 0, 2); + lua_createtable(L, 0, 3); lua_pushnumber(L, queue->len); lua_setfield(L, -2, "len"); lua_pushnumber(L, queue->owner_id); lua_setfield(L, -2, "owner"); + lua_pushboolean(L, queue->promote_is_latched); + lua_setfield(L, -2, "latched"); lua_setfield(L, -2, "queue"); return 1; diff --git a/src/box/txn_limbo.c b/src/box/txn_limbo.c index 70447caaf..3363e2f9a 100644 --- a/src/box/txn_limbo.c +++ b/src/box/txn_limbo.c @@ -47,6 +47,8 @@ txn_limbo_create(struct txn_limbo *limbo) vclock_create(&limbo->vclock); vclock_create(&limbo->promote_term_map); limbo->promote_greatest_term = 0; + latch_create(&limbo->promote_latch); + limbo->promote_is_latched = false; limbo->confirmed_lsn = 0; limbo->rollback_count = 0; limbo->is_in_rollback = false; @@ -724,11 +726,14 @@ txn_limbo_wait_empty(struct txn_limbo *limbo, double timeout) } void -txn_limbo_process(struct txn_limbo *limbo, const struct synchro_request *req) +txn_limbo_apply(struct txn_limbo *limbo, + const struct synchro_request *req) { + assert(latch_is_locked(&limbo->promote_latch)); + uint64_t term = req->term; uint32_t origin = req->origin_id; - if (txn_limbo_replica_term(limbo, origin) < term) { + if (vclock_get(&limbo->promote_term_map, origin) < (int64_t)term) { vclock_follow(&limbo->promote_term_map, origin, term); if (term > limbo->promote_greatest_term) limbo->promote_greatest_term = term; @@ -786,6 +791,15 @@ txn_limbo_process(struct txn_limbo *limbo, const struct synchro_request *req) return; } +void +txn_limbo_process(struct txn_limbo *limbo, + const struct synchro_request *req) +{ + txn_limbo_begin(limbo); + txn_limbo_apply(limbo, req); + txn_limbo_commit(limbo); +} + void txn_limbo_on_parameters_change(struct txn_limbo *limbo) { diff --git a/src/box/txn_limbo.h b/src/box/txn_limbo.h index 53e52f676..b9dddda77 100644 --- a/src/box/txn_limbo.h +++ b/src/box/txn_limbo.h @@ -31,6 +31,7 @@ */ #include "small/rlist.h" #include "vclock/vclock.h" +#include "latch.h" #include @@ -147,6 +148,14 @@ struct txn_limbo { * limbo and raft are in sync and the terms are the same. */ uint64_t promote_greatest_term; + /** + * To order access to the promote data. + */ + struct latch promote_latch; + /** + * A flag to inform if limbo is locked (for tests mostly). + */ + bool promote_is_latched; /** * Maximal LSN gathered quorum and either already confirmed in WAL, or * whose confirmation is in progress right now. Any attempt to confirm @@ -216,7 +225,7 @@ txn_limbo_last_entry(struct txn_limbo *limbo) * @a replica_id. */ static inline uint64_t -txn_limbo_replica_term(const struct txn_limbo *limbo, uint32_t replica_id) +txn_limbo_replica_term(struct txn_limbo *limbo, uint32_t replica_id) { return vclock_get(&limbo->promote_term_map, replica_id); } @@ -226,11 +235,14 @@ txn_limbo_replica_term(const struct txn_limbo *limbo, uint32_t replica_id) * data from it. The check is only valid when elections are enabled. */ static inline bool -txn_limbo_is_replica_outdated(const struct txn_limbo *limbo, +txn_limbo_is_replica_outdated(struct txn_limbo *limbo, uint32_t replica_id) { - return txn_limbo_replica_term(limbo, replica_id) < - limbo->promote_greatest_term; + latch_lock(&limbo->promote_latch); + uint64_t v = vclock_get(&limbo->promote_term_map, replica_id); + bool res = v < limbo->promote_greatest_term; + latch_unlock(&limbo->promote_latch); + return res; } /** @@ -300,7 +312,37 @@ txn_limbo_ack(struct txn_limbo *limbo, uint32_t replica_id, int64_t lsn); int txn_limbo_wait_complete(struct txn_limbo *limbo, struct txn_limbo_entry *entry); -/** Execute a synchronous replication request. */ +/** + * Initiate execution of a synchronous replication request. + */ +static inline void +txn_limbo_begin(struct txn_limbo *limbo) +{ + latch_lock(&limbo->promote_latch); + limbo->promote_is_latched = true; +} + +/** Commit a synchronous replication request. */ +static inline void +txn_limbo_commit(struct txn_limbo *limbo) +{ + latch_unlock(&limbo->promote_latch); + limbo->promote_is_latched = false; +} + +/** Rollback a synchronous replication request. */ +static inline void +txn_limbo_rollback(struct txn_limbo *limbo) +{ + latch_unlock(&limbo->promote_latch); +} + +/** Apply a synchronous replication request after processing stage. */ +void +txn_limbo_apply(struct txn_limbo *limbo, + const struct synchro_request *req); + +/** Process a synchronous replication request. */ void txn_limbo_process(struct txn_limbo *limbo, const struct synchro_request *req); -- 2.34.1