mysqldump for AWS RDS `flush tables` error on linux only

Question

I have a process that exports the data from an AWS RDS MariaDB using mysqldump which has been running succesfully in a docker-image on Concourse for years.

Since two nights ago the process has started failing with the error:

mysqldump: Couldn't execute 'FLUSH TABLES WITH READ LOCK': Access denied for user 'admin'@'%' (using password: YES) (1045)

The official AWS explanation seems to be that because they do not allow super privileges to the master user or GLOBAL READ LOCK the mysqldump fails if the --master-data option is set.

I do not have that option set. I'm running with these flags:

mysqldump -h ${SOURCE_DB_HOST} ${SOURCE_CREDENTIALS} ${SOURCE_DB_NAME} --single-transaction --compress | grep -v '^SET .*;$' > /tmp/dump.sql

mysqldump works fine when executed from my local Mac. It fails with the error that it couldn't execute FLUSH TABLES WITH READ LOCK only from the linux environment.

My question is, does anyone know how to disable the FLUSH TABLES WITH READ LOCK command in mysqldump on linux?

EDIT: Happy to accept @sergey-payu answer below as having fixed my problem, but here's a link to the MySQL bug report for the benefit of anyone else coming across this issue https://bugs.mysql.com/bug.php?id=109685

Answer 1

I faced the same issue couple of days ago. My mysqldump script had been working for years just fine until it started to give me the Access denied; you need (at least one of) the RELOAD privilege(s) for this operation Access denied; you need (at least one of) the RELOAD privilege(s) for this operation error. My first instinct was to grant this privilege. But after that I started to get Access denied for user 'user'@'%' (using password: YES) (1045) error, which is documented in AWS docs . After couple hours of investigation it turned out to be a bug of the most recent 5.7.41 version of mysql (It was released 17th of January, exactly when we started to get errors). Downgrading to 5.7.40 solved the problem. It's interesting that 5.7.41 changelog doesn't list anything close to the FLUSH TABLES WITH READ LOCK or to default values.

Answer 2

According to the 5.7.41 changelog,

The data and the GTIDs backed up by mysqldump were inconsistent when the options --single-transaction and --set-gtid-purged=ON were both used. It was because GTID_EXECUTED was fetched at the end of the dump, at which point the GTIDs on the server could have increased already. With this fixed, a FLUSH TABLES WITH READ LOCK is performed at the beginning of the dump and GTID_EXECUTED was fetched right after, to ensure its value is consistent with the snapshot taken by mysqldump.