Allow proxysql checks to specify stats database name

[tabacco]

What does this PR do?

Allow the instance config for the proxysql check to set an alternate database name to run stats queries against.

Motivation

The previosuly-hardcoded stats database is correct if you're connected as an admin user, but doesn't exist if you're connected as a stats-only user.

From a security point of view, it's probably better for datadog to connect as a stats user, since those aren't granted access to sensitive data. The existing checks should all work as a stats user, but for those users the 'stats' database is called 'main' instead.

Additional Notes

The default config for database_name is the same as the previously hardcoded name in the queries, so this should be backwards compatible.

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests (unit, integration, e2e)
• PR title must be written as a CHANGELOG entry (see why)
• Files changes must correspond to the primary purpose of the PR as described in the title (small unrelated changes should have their own PR)
• PR must have changelog/ and integration/ labels attached

[ruthnaebeck]

Docs review

[codecov]

Codecov Report

Merging #6835 into master will increase coverage by 3.67%.
The diff coverage is 100.00%.

Impacted Files	Coverage Δ
proxysql/datadog_checks/proxysql/queries.py	100.00% <ø> (ø)
proxysql/datadog_checks/proxysql/proxysql.py	95.52% <100.00%> (+4.61%)	⬆️
proxysql/tests/conftest.py	100.00% <100.00%> (ø)
proxysql/tests/test_proxysql.py	97.72% <100.00%> (+0.16%)	⬆️
druid/tests/conftest.py
consul/tests/test_unit.py
datadog_checks_dev/datadog_checks/dev/jmx.py
...atadog_checks_dev/datadog_checks/dev/conditions.py
sqlserver/datadog_checks/sqlserver/__about__.py
envoy/datadog_checks/envoy/__init__.py
... and 870 more

[tabacco]

By the way, I don't appear to have permission to add labels. I'm guessing that's what the "PR Labels / apply" action that failed was supposed to do - if anyone has any thoughts on why it's failing, I'd appreciate it.

[ruthnaebeck]

👍 for docs

[AlexandreYang]

Hi @tabacco ,

It seems passing database to pymysql.connect() has no effect. Removing stats. prefix from queries seems enough.

It's possibly due to the fact that stats users (listed in stats_credentials) are limited (defaulted) to stats database.

A user that connects to Admin with admin-stats_credentials credentials can only access this schema.

Any though on this ?

---

Note: somehow, queries like SELECT * FROM stats_mysql_global also work for admin users (proxy) even though the "selected database" is "admin".

root@4ba27ac178ac:/# mysql -u proxy -pproxy -h proxysql -P6032 --prompt='Admin> '
Admin> select database();
+------------+
| DATABASE() |
+------------+
| admin      |
+------------+
1 row in set (0.00 sec)

Admin> SELECT * FROM stats_mysql_query_rules;
+---------+------+
| rule_id | hits |
+---------+------+
| 1       | 0    |
+---------+------+
1 row in set (0.01 sec)

[tabacco]

Well that's interesting. It didn't occur to me to not try specifying the db name. I wonder if that's a byproduct of the fact that proxysql's admin database is actually sqlite.