MySQL: After a certain amount of time/transactions connections freeze during spec tests

[kalinon]

I found that after a certain amount of time/transactions (its unclear which one) spec tests will hang when running against a mysql server.

I was able to add debug and get this traced down to the DB adapter layer where it starts to read a packet but never completes:

2023-04-26T22:01:59.604210Z  DEBUG - db: Executing query -- query: "INSERT INTO `kvs` (`v`, `k`) VALUES (?, ?)", args: [nil, "foo"]
2023-04-26T22:01:59.604372Z  TRACE - db: About to execute query
2023-04-26T22:01:59.604419Z  TRACE - mysql: About to execute query
2023-04-26T22:01:59.604465Z  TRACE - mysql: #<MySql::Connection:0x103b95a20>
2023-04-26T22:01:59.604513Z  TRACE - mysql: write start - #<MySql::WritePacket:0x1074826e0>
2023-04-26T22:01:59.604564Z  TRACE - mysql: write done - #<MySql::WritePacket:0x1074826e0>
2023-04-26T22:01:59.604698Z  TRACE - mysql: read start - MySql::IncomingPacket[length: 5, seq: 4, remaining: 5]

I was able to complete a full spec run only if i manually closed all the connections in the connection pool.

# added to spec_helper.cr
Spec.after_each do
  Granite::Connections["mysql"].not_nil!.database.pool.close
end

I will keep investigating.

[robacarp]

Interesting. If that's true, this is probably a bug in the MySQL Adapter rather than in granite.

[kalinon]

Interesting. If that's true, this is probably a bug in the MySQL Adapter rather than in granite.

Yeah, i found it curious. If i do the specs in random order, it will freeze at different places, but always after a majority of specs are completed. I need to verify its not just my MySQL server or something local.

[crimson-knight]

The fact that it works when you force close all the connections makes me think there are being closed properly from some operations.

Which does seem like a bug in the MySQL adapter.

Does CI behave the same way? Or does it change between Crystal versions?

[kalinon]

@crimson-knight yes, CI behaves the same as does differences between crystal versions.

Versions Tested:

Crystal: 1.6.2, 1.7.2, 1.8.1
Mysql: 5.7, 8.0