nixpkgs/nixos/modules/services/backup/postgresql-backup.nix
Robert Hensing 81c8189a84 nixos/postgresqlBackup: Only replace backup when successful
Previously, a failed backup would always overwrite ${db}.sql.gz,
because the bash `>` redirect truncates the file; even if the
backup was going to fail.
On the next run, the ${db}.prev.sql.gz backup would be
overwritten by the bad ${db}.sql.gz.

Now, if the backup fails, the ${db}.in-progress.sql.gz is in an
unknown state, but ${db}.sql.gz will not be written.
On the next run, ${db}.prev.sql.gz (our only good backup) will
not be overwritten because ${db}.sql.gz does not exist.
2021-06-05 15:09:27 +02:00

136 lines
3.7 KiB
Nix

{ config, lib, pkgs, ... }:
with lib;
let
cfg = config.services.postgresqlBackup;
postgresqlBackupService = db: dumpCmd:
{
enable = true;
description = "Backup of ${db} database(s)";
requires = [ "postgresql.service" ];
path = [ pkgs.coreutils pkgs.gzip config.services.postgresql.package ];
script = ''
set -e -o pipefail
umask 0077 # ensure backup is only readable by postgres user
if [ -e ${cfg.location}/${db}.sql.gz ]; then
mv ${cfg.location}/${db}.sql.gz ${cfg.location}/${db}.prev.sql.gz
fi
${dumpCmd} | \
gzip -c > ${cfg.location}/${db}.in-progress.sql.gz
mv ${cfg.location}/${db}.in-progress.sql.gz ${cfg.location}/${db}.sql.gz
'';
serviceConfig = {
Type = "oneshot";
User = "postgres";
};
startAt = cfg.startAt;
};
in {
imports = [
(mkRemovedOptionModule [ "services" "postgresqlBackup" "period" ] ''
A systemd timer is now used instead of cron.
The starting time can be configured via <literal>services.postgresqlBackup.startAt</literal>.
'')
];
options = {
services.postgresqlBackup = {
enable = mkEnableOption "PostgreSQL dumps";
startAt = mkOption {
default = "*-*-* 01:15:00";
type = with types; either (listOf str) str;
description = ''
This option defines (see <literal>systemd.time</literal> for format) when the
databases should be dumped.
The default is to update at 01:15 (at night) every day.
'';
};
backupAll = mkOption {
default = cfg.databases == [];
defaultText = "services.postgresqlBackup.databases == []";
type = lib.types.bool;
description = ''
Backup all databases using pg_dumpall.
This option is mutual exclusive to
<literal>services.postgresqlBackup.databases</literal>.
The resulting backup dump will have the name all.sql.gz.
This option is the default if no databases are specified.
'';
};
databases = mkOption {
default = [];
type = types.listOf types.str;
description = ''
List of database names to dump.
'';
};
location = mkOption {
default = "/var/backup/postgresql";
type = types.path;
description = ''
Location to put the gzipped PostgreSQL database dumps.
'';
};
pgdumpOptions = mkOption {
type = types.separatedString " ";
default = "-C";
description = ''
Command line options for pg_dump. This options is not used
if <literal>config.services.postgresqlBackup.backupAll</literal> is enabled.
Note that config.services.postgresqlBackup.backupAll is also active,
when no databases where specified.
'';
};
};
};
config = mkMerge [
{
assertions = [{
assertion = cfg.backupAll -> cfg.databases == [];
message = "config.services.postgresqlBackup.backupAll cannot be used together with config.services.postgresqlBackup.databases";
}];
}
(mkIf cfg.enable {
systemd.tmpfiles.rules = [
"d '${cfg.location}' 0700 postgres - - -"
];
})
(mkIf (cfg.enable && cfg.backupAll) {
systemd.services.postgresqlBackup =
postgresqlBackupService "all" "pg_dumpall";
})
(mkIf (cfg.enable && !cfg.backupAll) {
systemd.services = listToAttrs (map (db:
let
cmd = "pg_dump ${cfg.pgdumpOptions} ${db}";
in {
name = "postgresqlBackup-${db}";
value = postgresqlBackupService db cmd;
}) cfg.databases);
})
];
}