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segments-web home page won't display if regression tests DB or backups DB is inaccessible

As discussed in more detail here, segments-web.ligo.org displays information on recent regression tests and DB backups on the home page, as Recent Interface/Integrity Tests and Recent Back-ups that show up in the Dataset Info box on the RHS of the home page. That information comes from segments-backup, through a connection by MariaDB. If that connection can't be made, the segments-web home page won't display, displaying one of a variety of errors, which depend on the cause of the problem, instead. [1] (This is probably an overlooked programming bug, not intentional behavior, as there is no reason not to display the page without those tables of links.) Some specific causes and details are listed in the link above. Note that if the problem is just that segments-web can't get the info it needs from segments-backup, other segments-web pages should still load, such as the Monitoring page ( https://segments-web.ligo.org/?c=00008 ) and the Flags page ( https://segments-web.ligo.org/?c=35 ) - so checking those can help diagnose the problem. (I.e., if those load, the problem is probably with the MariaDB connection from segments-web to segments-backup, whereas if those won't load, the problem is probably something else.)

The fix would likely just replace the lists of links with messages about that info not being available.

[1] More details are available here, but possible error messages have text that starts with:

  • Fatal error: Uncaught exception 'PDOException' with message 'SQLSTATE[HY000] [2003] Can't connect to MySQL server on 'segments-backup.ligo.org' (113)' in /usr/share/dqsegdb_web/classes/DAO.php:50 [...]
  • Fatal error: Uncaught exception 'PDOException' with message 'SQLSTATE[HY000] [2003] Can't connect to MySQL server on 'segments-backup.ligo.org' (111)' in /usr/share/dqsegdb_web/classes/DAO.php:50 [...]
  • Fatal error: Uncaught exception 'PDOException' with message 'SQLSTATE[28000] [1045] Access denied for user 'dqsegdb_web_user'@'segments-web-old.ligo.org' (using password: YES)' in /usr/share/dqsegdb_web/classes/DAO.php:50 [...]
  • Fatal error: Uncaught exception 'PDOException' with message 'SQLSTATE[HY000] [2002] Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (2)' in /usr/share/dqsegdb_web/classes/DAO.php:26 [...]
  • Warning: file_get_contents(http://10.14.0.101/report/db): failed to open stream: HTTP request failed! in /root/git/web/1.0/src/classes/GetServerData.php on line 124 [...]