Error establishing a database connection

The other day, my mam informed me that my website wasn’t working. She was right: it was showing an error message: “Error establishing a database connection”. Oh noes.

I googled the message; one result told me check whether the error occurred just on the front end or both the back end and the front end. It was both.

I rummaged around the internet further, and discovered I could start the database up again by typing
sudo /etc/init.d/mysql start
at the command line while sshing to the server. This fixed the whole problem — or so it seemed. A few hours later, when I looked again, the error message was back. I left it for a while.

Just now, I had another look at it. I restarted the database, as above, and then tried the repair database method, while the database was actually up and running. The results were that the database was all fine. I thought it would be: I had already used Sequel Pro to check it for myself. I should have maybe tried to connect to it before I restarted it, just to see. Oh well — I’m sure there’ll be another opportunity in the future.

The advice given on a Digital Ocean community page is to check the log file. Unfortunately, it doesn’t say how to find the log file.

I found the answer on a superuser page: do some complicated-looking greppy thing:
sudo ls -l `pgrep mysqld | sed 's@.*@/proc/&/fd/@'` | grep log
Note I had to use sudo, whereas the web page didn’t mention it.

Then, once I’d found it, I had to look at it. I made up a command to do this, which surprisingly enough, worked:
sudo view /var/log/mysql/error.log
Sadly, this opened Vim, which I dislike as much as I dislike Emacs. I copied and pasted the text into a proper text editor, then tried pressing Ctrl-C to get rid of Vim. It told me to type :quit followed by the Enter key. That seemed to work.

The most useful lines in the error log are perhaps these:

InnoDB: The log sequence number in ibdata files does not match
InnoDB: the log sequence number in the ib_logfiles!
160613  9:08:00  InnoDB: Database was not shut down normally!
InnoDB: Starting crash recovery.

However, I don’t know what what that really means or what caused the database to shut down abnormally. Le sigh.

I think I’ll just not worry about it unless it happens again. Hopefully, it won’t.

Do you want to reply?

This site uses Akismet to reduce spam. Learn how your comment data is processed.