MySQL hangs on SELECT from table with blob fields
https://dba.stackexchange.com/questions/282498
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13-03-2021 - |
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I managed to create a mysql 8 InnoDB cluster with three nodes (VPS in one dedicated server, 25GB ram in each VPS, Total RAM in the server 96GB) and MySQL Router 8 everything works great but when I try to run a select query from the table below from another server it freezes, but it works when I limit the result to a number under 26
SET NAMES utf8;
SET time_zone = '+00:00';
SET NAMES utf8mb4;
DROP TABLE IF EXISTS `v7_addad`;
CREATE TABLE `v7_addad` (
`id` int NOT NULL AUTO_INCREMENT,
`body` text CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NOT NULL,
`page_id` int NOT NULL,
`done` tinyint NOT NULL DEFAULT '0',
`book` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NOT NULL,
PRIMARY KEY (`id`),
FULLTEXT KEY `body` (`body`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_general_ci;
For example :
select * from v7_addad limit 25; # this works
select * from v7_addad limit 26; # this freezes
BTW it doesn't freeze when the MySQL Router is in the same server as the application.
Just want to add this I tested from localhost and I can get the result even without limit. so maybe it's a configuration or network issue. but I don't know how I can tackle this
[mysqld]
pid-file = /var/run/mysqld/mysqld.pid
socket = /var/run/mysqld/mysqld.sock
datadir = /var/lib/mysql
log-error = /var/log/mysql/error.log
key_buffer_size = 5G
table_open_cache = 3072
table_definition_cache = 4096
innodb_buffer_pool_size = 15G
innodb_buffer_pool_instances = 2
innodb_log_file_size = 2047M
max_allowed_packet = 64M
'SHOW PROCESSLIST' while the "freeze" is happening mysql> SHOW PROCESSLIST;
| Id | User | Host | db | Command | Time | State | Info |
| 6 | event_scheduler | localhost | NULL | Daemon | 285970 | Waiting on empty queue | NULL |
| 10 | system user | | NULL | Connect | 285970 | waiting for handler commit | Group replication applier module |
| 13 | system user | | NULL | Query | 285970 | Slave has read all relay log; waiting for more updates | NULL |
| 619140 | micadmin | LinuxSQL01.**.***.**.*:51896 | db0003 | Sleep | 535 | | NULL |
| 620298 | micadmin | LinuxSQL01.**.***.**.*:54218 | db0003 | Sleep | 3 | | NULL |
| 620304 | mysql_router1_g2wcum04fipm | LinuxSQL01.**.***.**.*:54230 | NULL | Sleep | 0 | | NULL |
| 620305 | micadmin | LinuxSQL01.**.***.**.*:54234 | NULL | Query | 0 | init | SHOW PROCESSLIST |
'SHOW ENGINE INNODB STATUS' while the "freeze" is happening
mysql > SHOW ENGINE INNODB STATUS;
| Type | Name | Status
| InnoDB | |
=====================================
2021-01-03 23:44:29 0x7f85843b4700 INNODB MONITOR OUTPUT
=====================================
Per second averages calculated from the last 13 seconds
-----------------
BACKGROUND THREAD
-----------------
srv_master_thread loops: 59377 srv_active, 0 srv_shutdown, 226562 srv_idle
srv_master_thread log flush and writes: 0
----------
SEMAPHORES
----------
OS WAIT ARRAY INFO: reservation count 642
OS WAIT ARRAY INFO: signal count 972
RW-shared spins 449, rounds 449, OS waits 0
RW-excl spins 227, rounds 6734, OS waits 207
RW-sx spins 1, rounds 1, OS waits 0
Spin rounds per wait: 1.00 RW-shared, 29.67 RW-excl, 1.00 RW-sx
------------
TRANSACTIONS
------------
Trx id counter 298328
Purge done for trx's n:o < 298327 undo n:o < 0 state: running but idle
History list length 3
LIST OF TRANSACTIONS FOR EACH SESSION:
---TRANSACTION 421696252935760, not started
0 lock struct(s), heap size 1136, 0 row lock(s)
---TRANSACTION 421696252933192, not started
0 lock struct(s), heap size 1136, 0 row lock(s)
---TRANSACTION 421696252934904, not started
0 lock struct(s), heap size 1136, 0 row lock(s)
---TRANSACTION 421696252934048, not started
0 lock struct(s), heap size 1136, 0 row lock(s)
---TRANSACTION 421696252932336, not started
0 lock struct(s), heap size 1136, 0 row lock(s)
---TRANSACTION 421696252931480, not started
0 lock struct(s), heap size 1136, 0 row lock(s)
---TRANSACTION 421696252930624, not started
0 lock struct(s), heap size 1136, 0 row lock(s)
---TRANSACTION 421696252929768, not started
0 lock struct(s), heap size 1136, 0 row lock(s)
--------
FILE I/O
--------
I/O thread 0 state: waiting for completed aio requests (insert buffer thread)
I/O thread 1 state: waiting for completed aio requests (log thread)
I/O thread 2 state: waiting for completed aio requests (read thread)
I/O thread 3 state: waiting for completed aio requests (read thread)
I/O thread 4 state: waiting for completed aio requests (read thread)
I/O thread 5 state: waiting for completed aio requests (read thread)
I/O thread 6 state: waiting for completed aio requests (write thread)
I/O thread 7 state: waiting for completed aio requests (write thread)
I/O thread 8 state: waiting for completed aio requests (write thread)
I/O thread 9 state: waiting for completed aio requests (write thread)
Pending normal aio reads: [0, 0, 0, 0] , aio writes: [0, 0, 0, 0] ,
ibuf aio reads:, log i/o's:, sync i/o's:
Pending flushes (fsync) log: 0; buffer pool: 18446744073709551516
5244 OS file reads, 1279100 OS file writes, 997056 OS fsyncs
0.00 reads/s, 0 avg bytes/read, 3.69 writes/s, 3.23 fsyncs/s
-------------------------------------
INSERT BUFFER AND ADAPTIVE HASH INDEX
-------------------------------------
Ibuf: size 1, free list len 0, seg size 2, 0 merges
merged operations:
insert 0, delete mark 0, delete 0
discarded operations:
insert 0, delete mark 0, delete 0
Hash table size 3984439, node heap has 2 buffer(s)
Hash table size 3984439, node heap has 1 buffer(s)
Hash table size 3984439, node heap has 1 buffer(s)
Hash table size 3984439, node heap has 2 buffer(s)
Hash table size 3984439, node heap has 1 buffer(s)
Hash table size 3984439, node heap has 3 buffer(s)
Hash table size 3984439, node heap has 4 buffer(s)
Hash table size 3984439, node heap has 7 buffer(s)
0.23 hash searches/s, 1.62 non-hash searches/s
---
LOG
---
Log sequence number 2270625140
Log buffer assigned up to 2270625140
Log buffer completed up to 2270625140
Log written up to 2270625140
Log flushed up to 2270625140
Added dirty pages up to 2270625140
Pages flushed up to 2270624443
Last checkpoint at 2270624443
413027 log i/o's done, 1.36 log i/o's/second
----------------------
BUFFER POOL AND MEMORY
----------------------
Total large memory allocated 16483614720
Dictionary memory allocated 1956558
Buffer pool size 983040
Free buffers 977582
Database pages 5437
Old database pages 2006
Modified db pages 1
Pending reads 0
Pending writes: LRU 0, flush list 0, single page 0
Pages made young 209, not young 0
0.00 youngs/s, 0.00 non-youngs/s
Pages read 5172, created 268, written 603288
0.00 reads/s, 0.00 creates/s, 0.00 writes/s
Buffer pool hit rate 1000 / 1000, young-making rate 0 / 1000 not 0 / 1000
Pages read ahead 0.00/s, evicted without access 0.00/s, Random read ahead 0.00/s
LRU len: 5437, unzip_LRU len: 0
I/O sum[258]:cur[0], unzip sum[0]:cur[0]
----------------------
INDIVIDUAL BUFFER POOL INFO
----------------------
---BUFFER POOL 0
Buffer pool size 491520
Free buffers 488755
Database pages 2754
Old database pages 996
Modified db pages 1
Pending reads 0
Pending writes: LRU 0, flush list 0, single page 0
Pages made young 209, not young 0
0.00 youngs/s, 0.00 non-youngs/s
Pages read 2596, created 161, written 384262
0.00 reads/s, 0.00 creates/s, 0.00 writes/s
Buffer pool hit rate 1000 / 1000, young-making rate 0 / 1000 not 0 / 1000
Pages read ahead 0.00/s, evicted without access 0.00/s, Random read ahead 0.00/s
LRU len: 2754, unzip_LRU len: 0
I/O sum[129]:cur[0], unzip sum[0]:cur[0]
---BUFFER POOL 1
Buffer pool size 491520
Free buffers 488827
Database pages 2683
Old database pages 1010
Modified db pages 0
Pending reads 0
Pending writes: LRU 0, flush list 0, single page 0
Pages made young 0, not young 0
0.00 youngs/s, 0.00 non-youngs/s
Pages read 2576, created 107, written 219026
0.00 reads/s, 0.00 creates/s, 0.00 writes/s
Buffer pool hit rate 1000 / 1000, young-making rate 0 / 1000 not 0 / 1000
Pages read ahead 0.00/s, evicted without access 0.00/s, Random read ahead 0.00/s
LRU len: 2683, unzip_LRU len: 0
I/O sum[129]:cur[0], unzip sum[0]:cur[0]
--------------
ROW OPERATIONS
--------------
0 queries inside InnoDB, 0 queries in queue
0 read views open inside InnoDB
Process ID=3803, Main thread ID=140203552966400 , state=sleeping
Number of rows inserted 9, updated 56291, deleted 0, read 7084971
0.00 inserts/s, 0.23 updates/s, 0.00 deletes/s, 21.69 reads/s
Number of system rows inserted 56323, updated 1572, deleted 56302, read 128455
0.23 inserts/s, 0.00 updates/s, 0.00 deletes/s, 0.00 reads/s
----------------------------
END OF INNODB MONITOR OUTPUT
============================
Solution
The problem was because of MySQL router, I couldn't find a solution to the problem but I found a good alternative called is proxysql.
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