| Demonstrations of mysqld_qslower, the Linux eBPF/bcc version. |
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| mysqld_qslower traces queries served by a MySQL server, and prints those that |
| exceed a latency (query time) threshold. By default a threshold of 1 ms is |
| used. For example: |
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| # ./mysqld_qslower.py `pgrep -n mysqld` |
| Tracing MySQL server queries for PID 14371 slower than 1 ms... |
| TIME(s) PID MS QUERY |
| 0.000000 18608 130.751 SELECT * FROM words WHERE word REGEXP '^bre.*n$' |
| 2.921535 18608 130.590 SELECT * FROM words WHERE word REGEXP '^alex.*$' |
| 4.603549 18608 24.164 SELECT COUNT(*) FROM words |
| 9.733847 18608 130.936 SELECT count(*) AS count FROM words WHERE word REGEXP '^bre.*n$' |
| 17.864776 18608 130.298 SELECT * FROM words WHERE word REGEXP '^bre.*n$' ORDER BY word |
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| This traced 5 queries, 4 of which took about 130 milliseconds. |
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| A pgrep command was used to specify the PID of mysqld. |
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| In this example, a lower threshold is used of 0.1 ms: |
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| # ./mysqld_qslower.py `pgrep -n mysqld` 0.1 |
| Tracing MySQL server queries for PID 14371 slower than 0.1 ms... |
| TIME(s) PID MS QUERY |
| 0.000000 18608 24.201 SELECT COUNT(*) FROM words |
| 13.242390 18608 130.378 SELECT * FROM words WHERE word REGEXP '^bre.*n$' |
| 23.601751 18608 119.198 SELECT * FROM words WHERE word REGEXP '^zzzzzzzz$' |
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| It worked, but I'm not catching any faster queries in this example. Notice I |
| added a query that searched for "zzzzzzzz": it returned an empty set, and ran |
| 11 ms faster. |
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| A 0 ms threshold can be specified to trace all queries: |
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| # ./mysqld_qslower.py `pgrep -n mysqld` 0 |
| Tracing MySQL server queries for PID 14371 slower than 0 ms... |
| TIME(s) PID MS QUERY |
| 0.000000 18608 0.105 select @@version_comment limit 1 |
| 2.049312 18608 0.099 SELECT DATABASE() |
| 2.050666 18608 0.274 show databases |
| 2.051040 18608 0.176 show tables |
| 5.730044 18608 130.365 SELECT count(*) AS count FROM words WHERE word REGEXP '^bre.*n$' |
| 9.273837 18608 0.096 select 1 |
| 9.553742 18608 0.059 select 1 |
| 9.986087 18608 0.080 select 1 |
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| This includes an initialization of a mysql client command, and selecting the |
| database. I also added some "select 1;" queries, which do no work and return |
| quickly. |
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| USAGE: |
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| # ./mysqld_qslower.py -h |
| USAGE: mysqld_latency PID [min_ms] |
