MySQL performance_schema not working properly? - mysql

Question

I have MySQL 5.6.19 community server running on my Ubuntu 14.04. Lately I have been trying to monitor MySQL server using performance_schema. Previously I used to do this by running SHOW FULL PROCESSLIST query every 5 second using a cronjob.
I configured performance_schema.setup_consumers table as follows.
mysql> use performance_schema;
mysql> select * from setup_consumers;
+--------------------------------+---------+
| NAME | ENABLED |
+--------------------------------+---------+
| events_stages_current | NO |
| events_stages_history | NO |
| events_stages_history_long | NO |
| events_statements_current | YES |
| events_statements_history | NO |
| events_statements_history_long | NO |
| events_waits_current | NO |
| events_waits_history | NO |
| events_waits_history_long | NO |
| global_instrumentation | YES |
| thread_instrumentation | YES |
| statements_digest | YES |
+--------------------------------+---------+
By default the events_statements_history is not enabled. I enabled it as follows.
mysql> update setup_consumers set enabled="YES" where name="events_statements_history";
Query OK, 1 row affected (0.01 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> select * from setup_consumers;
+--------------------------------+---------+
| NAME | ENABLED |
+--------------------------------+---------+
| events_stages_current | NO |
| events_stages_history | NO |
| events_stages_history_long | NO |
| events_statements_current | YES |
| events_statements_history | YES |
| events_statements_history_long | NO |
| events_waits_current | NO |
| events_waits_history | NO |
| events_waits_history_long | NO |
| global_instrumentation | YES |
| thread_instrumentation | YES |
| statements_digest | YES |
+--------------------------------+---------+
Now enabled, the events_statements_history table should now be able to capture queries but somehow it is not. Following is the result.
mysql> select count(sql_text) from events_statements_history;
+-----------------+
| count(sql_text) |
+-----------------+
| 0 |
+-----------------+
I do not understand as to why it is not logging in any queries?

Answer 1

The performance schema records data when three conditions are met:
The running thread is instrumented
The instrument currently executed is enabled
The consumers for the data to record are enabled
Threads
By default, every thread (1) is instrumented.
To check if threads are instrumented:
select THREAD_ID, NAME, PROCESSLIST_ID, PROCESSLIST_USER, PROCESSLIST_HOST, INSTRUMENTED from threads;
To change which threads are instrumented by default, use table setup_actors.
Instruments
By default, instruments for statements (aka, queries), are enabled (2).
To see which queries are not instrumented:
select * from setup_instruments where name like "statement/%" and enabled='NO';
To instrument all queries:
update setup_instruments set enabled="YES" where name like "statement/%";
Consumers
By default, only a few consumers are instrumented (3).
To see which consumers are instrumented, or to change this, use select / update on table setup_consumers.
This part seems fine per the question, so check part (1) and (2).

Answer 2

As a side-note, if there is nothing inside the setup_% tables then you might need to enable the performance schema,
https://dev.mysql.com/doc/refman/5.5/en/performance-schema-quick-start.html