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Appliers need to verify foreign key constraints during normal operation, in multi-active topologies, and for this reason appliers are configured to enable FK checking. However, during node joining, in IST and latter catch up period, the node is still idle (from local connections), and only source for incoming transactions is the cluster sending certified write sets for applying. IST happens with parallel applying, and there is a possibility that foreign key check cause lock conflicts between appliers accessing FK child and parent tables. Also, the excessive FK checking will slow down IST process somewhat. For this reasons, we could relax FK checks for appliers during IST and catch up periods. The relaxed FK check mode should, however, be configurable e.g. by wsrep_mode flag: SKIP_APPLIER_FK_CHECKS_IN_IST. When this operation mode is set, and the node is processing IST or catch up, appliers should skip FK checking. Signed-off-by: Julius Goryavsky <julius.goryavsky@mariadb.com>
103 lines
2.4 KiB
Plaintext
103 lines
2.4 KiB
Plaintext
connection node_4;
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connection node_3;
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connection node_2;
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connection node_1;
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connection node_1;
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connection node_2;
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connection node_3;
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connection node_4;
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connection node_1;
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CREATE TABLE parent (
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id INT PRIMARY KEY
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) ENGINE=InnoDB;
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CREATE TABLE child (
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id INT PRIMARY KEY,
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parent_id INT,
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KEY (parent_id),
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CONSTRAINT FOREIGN KEY (parent_id) REFERENCES parent(id)
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) ENGINE=InnoDB;
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INSERT INTO parent VALUES (1), (2);
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connection node_4;
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SET SESSION wsrep_on = OFF;
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DELETE FROM parent;
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SET SESSION wsrep_on = ON;
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Shutting down server 4
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connection node_1;
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SET SESSION wsrep_on = ON;
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SET SESSION wsrep_sync_wait = 15;
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connection node_2;
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SET SESSION wsrep_on = ON;
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SET SESSION wsrep_sync_wait = 15;
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connection node_3;
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SET SESSION wsrep_on = ON;
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SET SESSION wsrep_sync_wait = 15;
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Server 4 left the cluster
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connection node_1;
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INSERT INTO child VALUES (1, 1);
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connection node_4;
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Restarting server 4 with disabled FK checks during IST
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include/assert_grep.inc [no FK constraint failure]
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Server 4
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SELECT COUNT(*) AS EXPECT_0 FROM parent;
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EXPECT_0
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0
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SELECT COUNT(*) AS EXPECT_1 FROM child;
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EXPECT_1
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1
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connection node_1;
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Server 1
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SELECT COUNT(*) AS EXPECT_2 FROM parent;
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EXPECT_2
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2
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SELECT COUNT(*) AS EXPECT_1 FROM child;
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EXPECT_1
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1
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connection node_2;
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Server 2
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SELECT COUNT(*) AS EXPECT_2 FROM parent;
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EXPECT_2
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2
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SELECT COUNT(*) AS EXPECT_1 FROM child;
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EXPECT_1
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1
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connection node_3;
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Server 3
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SELECT COUNT(*) AS EXPECT_2 FROM parent;
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EXPECT_2
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2
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SELECT COUNT(*) AS EXPECT_1 FROM child;
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EXPECT_1
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1
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Causing server 4 inconsistency with failed FK check on apply
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INSERT INTO child VALUES (2, 2);
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connection node_1;
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SET SESSION wsrep_on = ON;
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SET SESSION wsrep_sync_wait = 15;
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connection node_2;
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SET SESSION wsrep_on = ON;
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SET SESSION wsrep_sync_wait = 15;
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connection node_3;
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SET SESSION wsrep_on = ON;
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SET SESSION wsrep_sync_wait = 15;
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Server 4 is non-primary
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connection node_4;
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SET SESSION wsrep_on = OFF;
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include/assert_grep.inc [FK constraint failure]
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Restarting server 4 with enabled FK checks during IST
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SELECT COUNT(*) AS EXPECT_2 FROM parent;
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EXPECT_2
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2
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SELECT COUNT(*) AS EXPECT_2 FROM child;
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EXPECT_2
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2
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CALL mtr.add_suppression("Slave SQL: Could not execute Write_rows_v1 event");
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CALL mtr.add_suppression("Event 3 Write_rows_v1 apply failed");
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CALL mtr.add_suppression("Inconsistency detected: Inconsistent by consensus");
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CALL mtr.add_suppression("Failed to apply write set");
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DROP TABLE child;
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DROP TABLE parent;
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disconnect node_4;
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disconnect node_3;
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disconnect node_2;
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disconnect node_1;
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