RFC: mysqlBackup / postgresqlBackup filename patterns

[mguentner]

I am using both services to make (easy) backups of DBs, mostly within containers. For some databases it is interesting to keep a history, i.e. not overwriting the file.

Currently I am using this patch to have a unique name:

diff --git a/nixos/modules/services/backup/postgresql-backup.nix b/nixos/modules/services/backup/postgresql-backup.nix
index 4a5ebebc68..61b7934bac 100644
--- a/nixos/modules/services/backup/postgresql-backup.nix
+++ b/nixos/modules/services/backup/postgresql-backup.nix
@@ -9,7 +9,7 @@ let

   postgresqlBackupCron = db:
     ''
-      ${config.services.postgresqlBackup.period} root ${config.services.postgresql.package}/bin/pg_dump ${db} | ${gzip}/bin/gzip -c > ${location}/${db}.gz
+      ${config.services.postgresqlBackup.period} root ${config.services.postgresql.package}/bin/pg_dump ${db} | ${gzip}/bin/gzip -c > ${location}/${db}_$(date --iso-8601=minutes).gz
     '';

 in

I believe that this is useful for others as well, so I'd like to create a PR, but before I'd like to hear some opinions. My idea is to introduce services.postgresqlBackup.pattern which defaults to an empty string and if supplied will be appended so...

${config.services.postgresql.package}/bin/pg_dump ${db} | ${gzip}/bin/gzip -c > ${location}/${db}${optionalString (cfg.pattern != null) "_${cfg.pattern}"}.gz

This will however amass backups without deleting them. Some cleanup needs to be done manually or by another cronjob.

[fadenb]

I am currently doing something quite similiar. Perhaps the option to cleanup all but the last X backups should be included in the module?

[mguentner]

Deleting the last X backups is possible, however care must be taken that only backups of the respective module are removed by the script in this directory. Also for KISS reasons: if pattern = "$(date +%e)" a history of one month will be kept without any need for deletion.

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