MySQL Database not reachable in fresh Confluence installation

Question

Hello all!
To migrate my existing confluence 6.x instance from an old server to a new one, I stuck in "connecting" confluence in a frsh installation.
What I have done so far (on new system):

OS: System Ubuntu 20.04 LTS
MySQL: 8.0 (8.0.26-0ubuntu0.20.04.2)
Confluence binary: atlassian-confluence-7.12.4-x64.bin
JDBC driver: mysql-connector-java-8.0.26.jar

Confluence installation runs without any errors.
I can connect MySQL via command line with usename/password for confluence.
All GRANTs are set properly.

Confluence setup runs until "Setup your database" -> "test connection"

After a while with this error message:

Can't reach database server or port
SQLState - 08S01
com.mysql.cj.jdbc.exceptions.CommunicationsException: Communications link failure The last packet sent successfully to the server was 0 milliseconds ago.
The driver has not received any packets from the server.

I've checked all advices like "connecting Confluence to a databse" and so on and double checked my installation parameters - and of course I've googled several hours ;-)

Does anyone have some ideas about this?

Thank's in advance!

Nic Brough -Adaptavist- · Answer

Nice!  Debugging database connections is always "fun", glad you've written up your case here to help others!

Frank Mittendorf · Answer

Hello Nic,

thank you for your hint!
I've figured out that a simple java test program has the same issue.
I'm gone into the depth and found out mysql connects through an UNIX socket on my machine. Changed it to TCP/IP but that did not solve the problem.
After that and many, many testing I've created another mysql user with access rights from host "127.0.0.1" without success.

On dev.mysql.com I found this page with several trouble shooting hints. Especially this test:

shell> mysqladmin -h `hostname` version variables

in combination with this hint:
Note the use of backticks rather than forward quotation marks with the hostname command; these cause the output of hostname.

I did this test (with connection failed of cource) but saw hostname resolves to "MYMACHINE". Now I've created an mysql user with access rights from "MYMACHINE".

Going back to Confluence setup "Setup your database" -> "test connection" filled under "hostname" "MYMACHINE" -> hit "Test connection"

=> that works!!! :-)

Hope it helps some other users ...

Nic Brough -Adaptavist- · Answer

That really does mean "your network is not letting me connect (reliably) to the database".  You'll need to start network tracing and monitoring if you think the port and server are fully available.