Missing DB connection closing

[brevilo]

Various BOINC components don't properly close the DB connection they opened before. This is a problem because:

• Open connections are a limited resource on the database server and new clients might be rejected when all are used up.
• Left-open connections will eventually be aborted by the database server and logged as a WARNING, at least by MariaDB. MySQL still logs it as INFORMATION but MariaDB has a good reason to warn about those: the root cause can in fact be caused by misconfiguration (e.g. max_allowed_packet) or networking issues. Both should not get masked by otherwise harmless missing connection closing.

Sampling only the current C API (e.g. used by daemons), you'll find:

• files issuing boinc_db.open(): 30
• files issuing boinc_db.close(): 9

This indicates a general issue, not just in the C API.

Thanks

[bema-aei]

Also the Db_conn of the web code (in html/inc/db_conn.inc) is lacking a method to close a DB connection.

[brevilo]

To be fair, in a web context it might be harder to decide if and when to close a connection as you might want to reuse it (opening connections is expensive). However, when you know it can be closed, it ought to be closed.

[bema-aei]

There should at least be the possibility given to do it. This is a generic general purpose class, not a specific page.