To summarise what I've posted in the forum messages, we've looked at
this issue with multiple versions of Mahara and different database
platforms.
Using a JMeter test plan that:
1) GET main index page
2) POST a login,
3) GET list of portfolios pages, i.e. /view/index.php
4) GET choose template page, i.e. /view/choosetemplate.php
5) POST to /view/choosetemplate.php the action equivalent to select a page to
copy (with all the appropriate form parameters)
Running this against Mahara 1.9, 1.10, or 15.04 and MySQL 5.5.44 -
deadlock bug occurs when multiple users copy pages at the same time.
It's relatively easy to trigger this, and I've included an example of
the deadlock below.
With PostgreSQL it's a different story. Running with either PostgreSQL
9.3 does not produce the deadlock errors, even when scaling up the test
to large numbers of simulated users copying pages. Tested with Mahara
15.04 and the current master branch from git. We believe this is also
true on PostgreSQL 8.4 (but have done far less testing with that
version).
Example MySQL deadlock message (from 'SHOW ENGINE INNODB STATUS'):
***************************************************************************
150916 20:46:31
*** (1) TRANSACTION:
TRANSACTION 1621D, ACTIVE 0 sec inserting
mysql tables in use 1, locked 1
LOCK WAIT 9 lock struct(s), heap size 1024, 5 row lock(s), undo log entries 2
MySQL thread id 222, OS thread handle 0x66480450, query id 9755 localhost
mahara update
INSERT INTO "view_rows_columns" ("view", "row", "columns") VALUES (17, 1, 3)
*** (1) WAITING FOR THIS LOCK TO BE GRANTED:
RECORD LOCKS space id 0 page no 2207 n bits 80 index "viewrowscolu_vie_ix" of
table "maharamaster"."view_rows_columns" trx id 1621D lock_mode X insert
intention waiting
Record lock, heap no 1 PHYSICAL RECORD: n_fields 1; compact format; info bits 0
0: len 8; hex 73757072656d756d; asc supremum;;
*** (2) TRANSACTION:
TRANSACTION 1620F, ACTIVE 0 sec inserting
mysql tables in use 1, locked 1
19 lock struct(s), heap size 1024, 12 row lock(s), undo log entries 7
MySQL thread id 219, OS thread handle 0x662ff450, query id 9771 localhost
mahara update
INSERT INTO "view_rows_columns" ("view", "row", "columns") VALUES ('15', 1, '3')
*** (2) HOLDS THE LOCK(S):
RECORD LOCKS space id 0 page no 2207 n bits 80 index "viewrowscolu_vie_ix" of
table "maharamaster"."view_rows_columns" trx id 1620F lock_mode X
Record lock, heap no 1 PHYSICAL RECORD: n_fields 1; compact format; info bits 0
0: len 8; hex 73757072656d756d; asc supremum;;
Record lock, heap no 13 PHYSICAL RECORD: n_fields 2; compact format; info bits
32
0: len 8; hex 800000000000000f; asc ;;
1: len 8; hex 8000000000000019; asc ;;
*** (2) WAITING FOR THIS LOCK TO BE GRANTED:
RECORD LOCKS space id 0 page no 2207 n bits 80 index "viewrowscolu_vie_ix" of
table "maharamaster"."view_rows_columns" trx id 1620F lock_mode X insert
intention waiting
Record lock, heap no 1 PHYSICAL RECORD: n_fields 1; compact format; info bits 0
0: len 8; hex 73757072656d756d; asc supremum;;
*** WE ROLL BACK TRANSACTION (1)
***************************************************************************
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https://bugs.launchpad.net/bugs/1492919
Title:
Deadlock issues when 20-30 users copying collections & pages at the
same time
Status in Mahara:
Triaged
Bug description:
Multiple users on the forum have reported deadlock issues when there
are many users (20-30) copying pages & collections at the same time.
See
https://mahara.org/interaction/forum/topic.php?id=7309&offset=0&limit=10
Note that 20 to 30 users is around the number you'd hit if you're
running a whole class of users through a training session at the same
time.
The three reported cases of this are all in 15.04, so it may be a
problem introduced in that version.
The problem has been reported in both Postgres & MySQL.
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