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Re: 21a84e23cf3: MDEV-16437: merge 5.7 P_S replication instrumentation and tables


Hello Sergei,

On 09/04/21 5:03 pm, Sergei Golubchik wrote:
Hi, Sujatha!

On Apr 09, sujatha wrote:
It looks that CONNECTION_RETRY_COUNT is 86400.
And 86400 is clearly a timeout, not a retry count.
Regarding the timeout, actually the above table just displays the user
specified connection configuration.

In case, user has not provided any value for 'CONNECTION_RETRY_COUNT' it
will hold the default value(86400).

   {"master-retry-count", 0,
    "The number of tries the slave will make to connect to the master before giving up.",
    &master_retry_count, &master_retry_count, 0, GET_ULONG,
    REQUIRED_ARG, 3600*24, 0, 0, 0, 0, 0},

this doesn't make any sense, why would retry *count* be set to the
number of seconds in a day? It's confusing. Is master retrying every

Actually there are two variables. When slave fails to establish a connection with master

it waits for '60' seconds. It attempts once again. This interval can be configured by

following following variable.


    The |MASTER_CONNECT_RETRY|option for |CHANGE MASTER|defines how many seconds that the replica will wait between connection retries. The default is |60|.     The number of connection attempts is limited by the master_retry_count <https://mariadb.com/kb/en/mysqld-options/#-master-retry-count>option.

The total number of retries by slave is controlled by following variable.


 * Commandline:|--master-retry-count=#|
 * Description:Number of times a slave will attempt to connect to a
   master before giving up. The retry interval is determined by the
   MASTER_CONNECT_RETRY option for the CHANGE MASTER statement. A value
   of 0 means the slave will not stop attempting to reconnect.
   Reconnects are triggered when a slave has timed out. See

 * Default Value:|86400|

May be I can configure some values instead of leaving them as defaults, and record them

in my test.

For example:

STOP SLAVE; CHANGE MASTER TO MASTER_CONNECT_RETRY=20; START SLAVE; [mariadb] ... master_retry_count=6000

If not - would you mind changing it to 80000? or 100000? Or something
else, whatever you like.

diff --git a/mysql-test/suite/rpl/include/rpl_deadlock.test b/mysql-test/suite/rpl/include/rpl_deadlock.test
index e9191d5fcd8..bccbe044a36 100644
--- a/mysql-test/suite/rpl/include/rpl_deadlock.test
+++ b/mysql-test/suite/rpl/include/rpl_deadlock.test
@@ -59,6 +59,16 @@ let $status_var_comparsion= >;
   connection slave;
+--echo # Test that the performance schema coulumn shows > 0 values.
+--let $assert_text= current number of retries should be more than the value saved before deadlock.
+--let $assert_cond= [SELECT COUNT_TRANSACTIONS_RETRIES FROM performance_schema.replication_applier_status, COUNT_TRANSACTIONS_RETRIES, 1] > "$slave_retried_transactions"
+--source include/assert.inc
what's wrong with simple

    SELECT COUNT_TRANSACTIONS_RETRIES > $slave_retried_transactions FROM performance_schema.replication_applier_status

'asserts' are preferred by upstream team and they find asserts to be
more readable rather than comparing SELECT OUTPUTS from result files.
I know. I always disliked assert.inc as mysqltest is perfectly capable
of comparing the expected result with an actual one and failing the test
on any difference. In fact, it's what mysqltest was written for in the
first place. assert.inc makes the result look prettier at the expence of
making the debugging much more difficult. Which, in my opinion, is a
wrong tradeoff, because nobody cares how pretty the result file is as
long as the test passes. But when the test fails, it's debugging that

But as we don't have a coding style that says "don't use assert.inc",
it's ultimately up to you.


VP of MariaDB Server Engineering
and security@xxxxxxxxxxx

Thank you.


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