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Bug#23074173 - NUMBER OF WORKER THREADS GOES UNDER MYSQLX_MIN_WORKER_THREADS
Description: There was a race-condition in scheduler.cc, comparation and decrementation of variable holding number of active workers was done in two instructions without any mutex guarding the access to it. Solution: Access to m_workers_count is now guarded by m_thread_worker_pending_mutex. Reviewed-by: Andrzej Religa <[email protected]> Reviewed-by: Grzegorz Szwarc <[email protected]> RB: 12370
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11 files changed

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‎mysql-test/suite/xplugin/r/bug23074173.result‎

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install plugin mysqlx soname "mysqlx.so";
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call mtr.add_suppression("Plugin mysqlx reported: .Failed at SSL configuration: .SSL context is not usable without certificate and private key..");
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call mtr.add_suppression("Plugin mysqlx reported: .SSL_CTX_load_verify_locations failed.");
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SET GLOBAL Mysqlx_min_worker_threads=50;
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SET GLOBAL Mysqlx_max_connections = 200;
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SET GLOBAL Mysqlx_idle_worker_thread_timeout=2;
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connecting...
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active session is now 'con 0'
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connecting...
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active session is now 'con 1'
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connecting...
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active session is now 'con 2'
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connecting...
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active session is now 'con 3'
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connecting...
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active session is now 'con 4'
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connecting...
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active session is now 'con 5'
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connecting...
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active session is now 'con 6'
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connecting...
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active session is now 'con 7'
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connecting...
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active session is now 'con 8'
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connecting...
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active session is now 'con 9'
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connecting...
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active session is now 'con 10'
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connecting...
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active session is now 'con 11'
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connecting...
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active session is now 'con 12'
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connecting...
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active session is now 'con 13'
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connecting...
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active session is now 'con 14'
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connecting...
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active session is now 'con 15'
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connecting...
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active session is now 'con 16'
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connecting...
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active session is now 'con 17'
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connecting...
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active session is now 'con 18'
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connecting...
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active session is now 'con 19'
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connecting...
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active session is now 'con 20'
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connecting...
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active session is now 'con 21'
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connecting...
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active session is now 'con 22'
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connecting...
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active session is now 'con 23'
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connecting...
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active session is now 'con 24'
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connecting...
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active session is now 'con 25'
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connecting...
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active session is now 'con 26'
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connecting...
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active session is now 'con 27'
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connecting...
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active session is now 'con 28'
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connecting...
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active session is now 'con 29'
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connecting...
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active session is now 'con 30'
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connecting...
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active session is now 'con 31'
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connecting...
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active session is now 'con 32'
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connecting...
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active session is now 'con 33'
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connecting...
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active session is now 'con 34'
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connecting...
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active session is now 'con 35'
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connecting...
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active session is now 'con 36'
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connecting...
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active session is now 'con 37'
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connecting...
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active session is now 'con 38'
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connecting...
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active session is now 'con 39'
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connecting...
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active session is now 'con 40'
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connecting...
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active session is now 'con 41'
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connecting...
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active session is now 'con 42'
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connecting...
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active session is now 'con 43'
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connecting...
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active session is now 'con 44'
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connecting...
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active session is now 'con 45'
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connecting...
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active session is now 'con 46'
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connecting...
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active session is now 'con 47'
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connecting...
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active session is now 'con 48'
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connecting...
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active session is now 'con 49'
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connecting...
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active session is now 'con 50'
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connecting...
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active session is now 'con 51'
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connecting...
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active session is now 'con 52'
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connecting...
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active session is now 'con 53'
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connecting...
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active session is now 'con 54'
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connecting...
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active session is now 'con 55'
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connecting...
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active session is now 'con 56'
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connecting...
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active session is now 'con 57'
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connecting...
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active session is now 'con 58'
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connecting...
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active session is now 'con 59'
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connecting...
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active session is now 'con 60'
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connecting...
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active session is now 'con 61'
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connecting...
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active session is now 'con 62'
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connecting...
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active session is now 'con 63'
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connecting...
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active session is now 'con 64'
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connecting...
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active session is now 'con 65'
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connecting...
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active session is now 'con 66'
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connecting...
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active session is now 'con 67'
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connecting...
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active session is now 'con 68'
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connecting...
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active session is now 'con 69'
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connecting...
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active session is now 'con 70'
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connecting...
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active session is now 'con 71'
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connecting...
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active session is now 'con 72'
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connecting...
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active session is now 'con 73'
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connecting...
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active session is now 'con 74'
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connecting...
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active session is now 'con 75'
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connecting...
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active session is now 'con 76'
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connecting...
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active session is now 'con 77'
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connecting...
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active session is now 'con 78'
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connecting...
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active session is now 'con 79'
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connecting...
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active session is now 'con 80'
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connecting...
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active session is now 'con 81'
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connecting...
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active session is now 'con 82'
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connecting...
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active session is now 'con 83'
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connecting...
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active session is now 'con 84'
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connecting...
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active session is now 'con 85'
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connecting...
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active session is now 'con 86'
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connecting...
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active session is now 'con 87'
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connecting...
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active session is now 'con 88'
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connecting...
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active session is now 'con 89'
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connecting...
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active session is now 'con 90'
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connecting...
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active session is now 'con 91'
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connecting...
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active session is now 'con 92'
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connecting...
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active session is now 'con 93'
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connecting...
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active session is now 'con 94'
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connecting...
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active session is now 'con 95'
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connecting...
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active session is now 'con 96'
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connecting...
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active session is now 'con 97'
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connecting...
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active session is now 'con 98'
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connecting...
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active session is now 'con 99'
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SHOW STATUS like 'mysqlx_worker_threads';
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Variable_name Value
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Mysqlx_worker_threads 50
210+
uninstall plugin mysqlx;

‎mysql-test/suite/xplugin/r/performance_schema.result‎

Lines changed: 9 additions & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -2,8 +2,8 @@ install plugin mysqlx soname "mysqlx.so";
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call mtr.add_suppression("Plugin mysqlx reported: .Failed at SSL configuration: .SSL context is not usable without certificate and private key..");
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call mtr.add_suppression("Plugin mysqlx reported: .SSL_CTX_load_verify_locations failed.");
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5-
7 rows affected
6-
Rows matched: 7 Changed: 0 Warnings: 0
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6 rows affected
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Rows matched: 6 Changed: 0 Warnings: 0
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1 rows affected
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Rows matched: 1 Changed: 1 Warnings: 0
@@ -26,24 +26,22 @@ thread/mysqlx/worker
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0 rows affected
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name
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wait/synch/mutex/mysqlx/lock_list_access
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wait/synch/mutex/mysqlx/scheduler_dynamic_post
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wait/synch/mutex/mysqlx/scheduler_dynamic_task_pending
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wait/synch/mutex/mysqlx/scheduler_dynamic_thread_exit
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wait/synch/mutex/mysqlx/scheduler_dynamic_worker_pending
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0 rows affected
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name
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wait/synch/cond/mysqlx/scheduler_dynamic_task_pending
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wait/synch/cond/mysqlx/scheduler_dynamic_thread_exit
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wait/synch/cond/mysqlx/scheduler_dynamic_worker_pending
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0 rows affected
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name
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wait/synch/rwlock/mysqlx/client_list_clients
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0 rows affected
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NAME ENABLED TIMED
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wait/synch/mutex/mysqlx/lock_list_access NO NO
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wait/synch/mutex/mysqlx/scheduler_dynamic_task_pending NO NO
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wait/synch/mutex/mysqlx/scheduler_dynamic_worker_pending NO NO
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wait/synch/mutex/mysqlx/scheduler_dynamic_thread_exit YES NO
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wait/synch/mutex/mysqlx/scheduler_dynamic_post YES NO
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wait/synch/rwlock/mysqlx/client_list_clients YES NO
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wait/synch/cond/mysqlx/scheduler_dynamic_task_pending NO NO
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wait/synch/cond/mysqlx/scheduler_dynamic_worker_pending NO NO
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wait/synch/cond/mysqlx/scheduler_dynamic_thread_exit YES NO
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0 rows affected
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@@ -175,13 +173,12 @@ thread/mysqlx/worker
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command ok
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name
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wait/synch/mutex/mysqlx/lock_list_access
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wait/synch/mutex/mysqlx/scheduler_dynamic_post
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wait/synch/mutex/mysqlx/scheduler_dynamic_task_pending
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wait/synch/mutex/mysqlx/scheduler_dynamic_thread_exit
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wait/synch/mutex/mysqlx/scheduler_dynamic_worker_pending
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command ok
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name
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wait/synch/cond/mysqlx/scheduler_dynamic_task_pending
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wait/synch/cond/mysqlx/scheduler_dynamic_thread_exit
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wait/synch/cond/mysqlx/scheduler_dynamic_worker_pending
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command ok
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name
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wait/synch/rwlock/mysqlx/client_list_clients
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EVENT_NAME
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UNINSTALL PLUGIN mysqlx;
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update performance_schema.setup_instruments set ENABLED='YES'
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where NAME rlike '^wait/synch/(cond|mutex)/mysqlx/(lock_list_access|scheduler_dynamic_task_pending)$';
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where NAME rlike '^wait/synch/(cond|mutex)/mysqlx/(lock_list_access|scheduler_dynamic_worker_pending)$';

‎mysql-test/suite/xplugin/t/bug23074173-master.opt‎

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--show_compatibility_56=1
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--plugin_dir=$MYSQLXPLUGIN_DIR
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--performance_schema_events_waits_history_long_size=400000

‎mysql-test/suite/xplugin/t/bug23074173.test‎

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## generated
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## Ping
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--source suite/xplugin/include/xplugin_preamble.inc
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SET GLOBAL Mysqlx_min_worker_threads=50;
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SET GLOBAL Mysqlx_max_connections = 200;
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SET GLOBAL Mysqlx_idle_worker_thread_timeout=2;
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--write_file $MYSQL_TMP_DIR/worker_threads.tmp
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-->repeat 100 %I%
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-->newsession con %I% root
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-->endrepeat
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-->abort
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EOF
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--error 2
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--exec $MYSQLXTEST -uroot --password='' --file=$MYSQL_TMP_DIR/worker_threads.tmp 2>&1
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let $wait_condition=
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SELECT VARIABLE_VALUE <51 FROM information_schema.GLOBAL_STATUS gs where VARIABLE_NAME = 'mysqlx_worker_threads';
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--source include/wait_condition.inc
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SHOW STATUS like 'mysqlx_worker_threads';
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--remove_file $MYSQL_TMP_DIR/worker_threads.tmp
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## Postamble
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uninstall plugin mysqlx;

‎mysql-test/suite/xplugin/t/performance_schema.test‎

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1313
update performance_schema.setup_instruments set ENABLED='YES' where NAME like '%mysqlx%';
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1515
update performance_schema.setup_instruments set ENABLED='NO' where NAME like 'wait/synch/mutex/mysqlx/lock_list_access';
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update performance_schema.setup_instruments set ENABLED='NO' where NAME like 'wait/synch/mutex/mysqlx/scheduler_dynamic_task_pending';
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update performance_schema.setup_instruments set ENABLED='NO' where NAME like 'wait/synch/cond/mysqlx/scheduler_dynamic_task_pending';
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update performance_schema.setup_instruments set ENABLED='NO' where NAME like 'wait/synch/mutex/mysqlx/scheduler_dynamic_worker_pending';
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update performance_schema.setup_instruments set ENABLED='NO' where NAME like 'wait/synch/cond/mysqlx/scheduler_dynamic_worker_pending';
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update performance_schema.setup_consumers set ENABLED='YES' where NAME like 'events_waits%';
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@@ -505,4 +505,4 @@ where EVENT_NAME rlike '^wait/synch/(cond|mutex)/mysqlx/(queue|client_session|ob
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## Postamble
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UNINSTALL PLUGIN mysqlx;
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update performance_schema.setup_instruments set ENABLED='YES'
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where NAME rlike '^wait/synch/(cond|mutex)/mysqlx/(lock_list_access|scheduler_dynamic_task_pending)$';
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where NAME rlike '^wait/synch/(cond|mutex)/mysqlx/(lock_list_access|scheduler_dynamic_worker_pending)$';

‎rapid/plugin/x/mysqlxtest_src/mysqlxtest.cc‎

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@@ -1539,7 +1539,11 @@ class Command
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{
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std::string s = args;
15411541
std::string user, pass, db, name;
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replace_variables(s);
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15421545
std::string::size_type p = s.find(CMD_ARG_SEPARATOR);
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15431547
if (p != std::string::npos)
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{
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name = s.substr(0, p);

‎rapid/plugin/x/ngs/include/ngs/scheduler.h‎

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@@ -67,7 +67,7 @@ namespace ngs
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bool is_worker_thread(my_thread_t thread_id);
6868
bool is_running();
6969
void join_terminating_workers();
70-
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7171
private:
7272
template<typename Element_type>
7373
class lock_list
@@ -138,14 +138,15 @@ namespace ngs
138138
return thread.thread == id;
139139
}
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141+
bool wait_if_idle_then_delete_worker();
141142
int32 increase_workers_count();
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int32 decrease_workers_count();
143144
int32 increase_tasks_count();
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int32 decrease_tasks_count();
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146147
const std::string m_name;
147-
Mutex m_task_pending_mutex;
148-
Cond m_task_pending_cond;
148+
Mutex m_worker_pending_mutex;
149+
Cond m_worker_pending_cond;
149150
Mutex m_thread_exit_mutex;
150151
Cond m_thread_exit_cond;
151152
Mutex m_post_mutex;

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