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  1. Percona Monitoring and Management
  2. PMM-10044

QAN stats dont add up - default values

Details

    • Bug
    • Status: Done
    • Medium
    • Resolution: Fixed
    • 2.27.0, 2.28.0
    • 2.31.0
    • PMM Server, QAN App
    • None
    • 1
    • Yes
    • Yes
    • [obsolete] C/S Core
    • Hide

      How to Repeat.
      1. Setup PMM Server
      2. Add MySQL Server with perf schema enabled
      3.
      – create 10K tables
      for i in `seq 1 1 10000`; do mysql PMM_10044 -e "CREATE TABLE t_$i(t_${i}1 int, t${i}2 int, t${i}3 int, t${i}4 int, t${i}5 int, t${i}6 int, t${i}7 int, t${i}8 int, t${i}9 int, t${i}10 int) engine=innodb; insert into t$i values(rand()*10000, rand()*10000, rand()*10000, rand()*10000, rand()*10000, rand()*10000, rand()*10000, rand()*10000, rand()*10000, rand()*10000);"; done

      – query them
      for i in `seq 1 1 10000`; do for j in `seq 1 1 10`; do mysql PMM_10044 -e "SELECT t_${i}${j} from t${i}" > /dev/null; done; done
      This script creates 10K tables, inserts one row into each of them, then queries each table 10 times. As you notice each query runs only once. However, QAN reports random big numbers for random queries (see attached screenshots):
      4. Wait for 5 minutes
      5. Check that QAN values are correct.

      Show
      How to Repeat. 1. Setup PMM Server 2. Add MySQL Server with perf schema enabled 3. – create 10K tables for i in `seq 1 1 10000`; do mysql PMM_10044 -e "CREATE TABLE t_$i(t_${i} 1 int, t ${i} 2 int, t ${i} 3 int, t ${i} 4 int, t ${i} 5 int, t ${i} 6 int, t ${i} 7 int, t ${i} 8 int, t ${i} 9 int, t ${i} 10 int) engine=innodb; insert into t $i values(rand()*10000, rand()*10000, rand()*10000, rand()*10000, rand()*10000, rand()*10000, rand()*10000, rand()*10000, rand()*10000, rand()*10000);"; done – query them for i in `seq 1 1 10000`; do for j in `seq 1 1 10`; do mysql PMM_10044 -e "SELECT t_${i} ${j} from t ${i}" > /dev/null; done; done This script creates 10K tables, inserts one row into each of them, then queries each table 10 times. As you notice each query runs only once. However, QAN reports random big numbers for random queries (see attached screenshots): 4. Wait for 5 minutes 5. Check that QAN values are correct.

    Description

      Customer updgraded from 2.26 to 2.27 and now 2.28

      There are videos attached to show the error that QAN stats dont match those on the summary page

      The "first video" if you look at the QPS on main dashboard at the figure but then go to QAN it seems to be registering 1000x to the value.

      in the "second video" starting on the node summary page... the server is doing next to nothing with a load average of 1 on a 96 vCPU instance.  yet if you look on QAN we're allegedly doing close to a million QPS!!! 

       

      Steps to reproduce are mentioned in comments by Sveta.

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              nurlan.moldomurov Nurlan Moldomurov
              mark.stephenson Mark Stephenson
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                Updated:
                Resolved:

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