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Old 01-24-2011, 12:57 PM   #1
jacppe
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Detect when Mysql has locked tables


Hi all, I'm running Mysql server. I need to know if is possible to generate an alert (email) when in the database are locked tables.
Is that possible?
Thanks a lot.
 
Old 01-24-2011, 02:06 PM   #2
EricTRA
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Hello,

Not sure if this is what you want but you could use the show open tables command on a database. If the output shows something like this:
Code:
mysql> show open tables from test;
+----------+-------+--------+-------------+
| Database | Table | In_use | Name_locked |
+----------+-------+--------+-------------+
| test     | tab1  |      3 |           0 |
+----------+-------+--------+-------------+
1 row in set (0.00 sec)
then the output in column In_use tells you how many threads are using this table, meaning have the table locked or waiting.

You could use that in a script (connect to DB first, then the command) and mail you if the output is positive.

Kind regards,

Eric

Last edited by EricTRA; 01-25-2011 at 12:48 AM.
 
Old 01-24-2011, 02:16 PM   #3
jacppe
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Quote:
Originally Posted by EricTRA View Post
Hello,

Not sure if this is what you want but you could use the show open tables command on a database. If the output shows something like this:
Code:
mysql> show open tables from test;
+----------+-------+--------+-------------+
| Database | Table | In_use | Name_locked |
+----------+-------+--------+-------------+
| mydb     | tab1  |      3 |           0 |
+----------+-------+--------+-------------+
1 row in set (0.00 sec)
then the output in column In_use tells you how many threads are using this table, meaning have the table locked or waiting.

You could use that in a script (connect to DB first, then the command) and mail you if the output is positive.

Kind regards,

Eric

Hi Eric, my idea is generate an alert when a table is locked state for more than xx seconds.
 
Old 01-25-2011, 12:57 AM   #4
EricTRA
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Hello,

I don't know if there exists a function within MySQL that can give you that output but you might include some function for it in your script.

If a table is not locked then your script should do nothing, right?
Say that you detect a table as locked using the show open tables command. You could save the status in a variable and enter in a loop that checks like every ten seconds (or whatever interval you want).
When the counter (number of checks x ten seconds for example) reaches 30 (5 minutes) send a mail that the table has been locked for ten minutes.

Most likely other users with more MySQL experience can put in something more useful but this is how I would do it for starters meanwhile looking for another solution.

Kind regards,

Eric
 
  


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