Database Infrastructure SOP
Our database servers provide database storage for many of our apps.
Fedora Infrastructure Team
#fedora-admin, sysadmin-main, sysadmin-dba group
sb01, db03, db-fas01, db-datanommer02, db-koji01, db-s390-koji01, db-arm-koji01, db-ppc-koji01, db-qa01, dbqastg01
Provides database connection to many of our apps.
db01, db03 and db-fas01 are our primary servers. db01 and db-fas01 run PostgreSQL. db03 contain mariadb. db-koji01, db-s390-koji01, db-arm-koji01, db-ppc-koji01 contain secondary kojis. db-qa01 and db-qastg01 contain resultsdb. db-datanommer02 contains all storage messages from postgresql database.
Creating a New Postgresql Database
Creating a new database on our postgresql server isn’t hard but there’s several steps that should be taken to make the database server as secure as possible.
We want to separate the database permissions so that we don’t have the user/password combination that can do anything it likes to the database on every host (the webapp user can usually do a lot of things even without those extra permissions but every little bit helps).
Say we have an app called "raffle". We’d have three users:
raffleadmin: able to make any changes they want to this particular database. It should not be used in day to day but only for things like updating the database schema when an update occurs. We could very likely disable this account in the db whenever we are not using it.
raffleapp: the database user that the web application uses. This will likely need to be able to insert and select from all tables. It will probably need to update most tables as well. There may be some tables that it does not need delete on. It should almost certainly not need schema modifying permissions. (With postgres, it likely also needs permission to insert/select on sequences as well).
rafflereadonly: Only able to read data from tables, not able to modify anything. Sadly, we aren’t using this often but it can be useful for scripts that need to talk directly to the database without modifying it.
db2 $ sudo -u postgres createuser -P -E NEWDBadmin Password: <randomly generated password> db2 $ sudo -u postgres createuser -P -E NEWDBapp Password: <randomly generated password> db2 $ sudo -u postgres createuser -P -E NEWDBreadonly Password: <randomly generated password> db2 $ sudo -u postgres createdb -E utf8 NEWDB -O NEWDBadmin db2 $ sudo -u postgres psql NEWDB NEWDB=# revoke all on database NEWDB from public; NEWDB=# revoke all on schema public from public; NEWDB=# grant all on schema public to NEWDBadmin; NEWDB=# [grant permissions to NEWDBapp as appropriate for your app] NEWDB=# [grant permissions to NEWDBreadonly as appropriate for a user that is only trusted enough to read information] NEWDB=# grant connect on database NEWDB to nagiosuser;
If your application needs to have the NEWDBapp and password to connect to the database, you probably want to add these to ansible as well. Put the password in the private repo in batcave01. Then use a templatefile to incorporate it into the config file. See fas.pp for an example.
Troubleshooting and Resolution
There are no known outstanding issues with the database itself. Remember that every time either database is restarted, services will have to be restarted (see Restart Procedure).
Some useful queries
What queries are running
This can help you find out what queries are cuurently running on the server:
select datname, pid, query_start, backend_start, query from pg_stat_activity where state<>'idle' order by query_start;
This can help you find how many connections to the db server are for each individual database:
select datname, count(datname) from pg_stat_activity group by datname order by count desc;
Seeing how "dirty" a table is
We’ve added a function from postgres’s contrib directory to tell how dirty a table is. By dirty we mean, how many tuples are active, how many have been marked as having old data (and therefore "dead") and how much free space is allocated to the table but not used.:
\c fas2 \x select * from pgstattuple('visit_identity'); table_len | 425984 tuple_count | 580 tuple_len | 46977 tuple_percent | 11.03 dead_tuple_count | 68 dead_tuple_len | 5508 dead_tuple_percent | 1.29 free_space | 352420 free_percent | 82.73 \x
Vacuum should clear out dead_tuples. Only a vacuum full, which will lock the table and therefore should be avoided, will clear out free space.
Find out how close we are to having to perform a vacuum of a database (as opposed to individual tables of the db). We should schedule a vacuum when about 50% of the transaction ids have been used (approximately 530,000,000 xids):
select datname, age(datfrozenxid), pow(2, 31) - age(datfrozenxid) as xids_remaining from pg_database order by xids_remaining;
If the database server needs to be restarted it should come back on its own. Otherwise each service on it can be restarted:
service mysqld restart service postgresql restart
Any time postgreql is restarted, koji needs to be restarted. Please also see Restarting Koji.
TurboGears and MySQL
About TurboGears and MySQL
There’s a known bug in TurboGears that causes MySQL clients not to automatically reconnect when lost. Typically a restart of the TurboGears application will correct this issue.
Restoring from backups or specific dbs.
Our backups store the latest copy in
/backups/ on each db server. These
backups are created automatically by the db-backup script run fron cron.
/usr/local/bin for the backup script.
To restore partially or completely you need to:
setup postgres on a system
start postgres/run initdb
if this new system running postgres has already run ansible then it will have wrong config files in
/var/lib/pgsql/data- clear them out before you start postgres so initdb can work.
grab the backups you need from
/backups- also grab global.sql
edit up global.sql to only create/alter the dbs you care about
as postgres run:
psql -U postgres -f global.sql
when this completes you can restore each db with (as postgres user)
createdb $dbname pg_restore -d dbname dbname_backup_file.db
restart postgres and check your data.
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