stockholm/krebs/3modules/backup.nix
2015-12-28 19:43:31 +01:00

287 lines
7.7 KiB
Nix

{ config, lib, pkgs, ... }:
with lib;
let
out = {
options.krebs.backup = api;
config = mkIf cfg.enable imp;
};
cfg = config.krebs.backup;
api = {
enable = mkEnableOption "krebs.backup" // { default = true; };
plans = mkOption {
default = {};
type = types.attrsOf (types.submodule ({
# TODO enable = mkEnableOption "TODO" // { default = true; };
options = {
method = mkOption {
type = types.enum ["pull" "push"];
};
name = mkOption {
type = types.str;
};
src = mkOption {
type = types.krebs.file-location;
};
dst = mkOption {
type = types.krebs.file-location;
};
startAt = mkOption {
type = types.str;
};
snapshots = mkOption {
type = types.attrsOf (types.submodule {
options = {
format = mkOption {
type = types.str; # TODO date's +FORMAT
};
retain = mkOption {
type = types.nullOr types.int;
default = null; # null = retain all snapshots
};
};
});
};
};
}));
};
};
imp = {
users.groups.backup.gid = genid "backup";
users.users = {}
// {
root.openssh.authorizedKeys.keys =
map (plan: plan.dst.host.ssh.pubkey)
(filter isPullSrc (attrValues cfg.plans))
++
map (plan: plan.src.host.ssh.pubkey)
(filter isPushDst (attrValues cfg.plans))
;
}
;
systemd.services =
flip mapAttrs' (filterAttrs (_:isPullDst) cfg.plans) (name: plan: {
name = "backup.${name}.pull";
value = makePullService plan;
})
//
flip mapAttrs' (filterAttrs (_:isPushSrc) cfg.plans) (name: plan: {
name = "backup.${name}.push";
value = makePushService plan;
})
;
};
isPushSrc = plan:
plan.method == "push" &&
plan.src.host.name == config.krebs.build.host.name;
isPullSrc = plan:
plan.method == "pull" &&
plan.src.host.name == config.krebs.build.host.name;
isPushDst = plan:
plan.method == "push" &&
plan.dst.host.name == config.krebs.build.host.name;
isPullDst = plan:
plan.method == "pull" &&
plan.dst.host.name == config.krebs.build.host.name;
# TODO push destination needs this in the dst.user's PATH
service-path = [
pkgs.coreutils
pkgs.gnused
pkgs.openssh
pkgs.rsync
pkgs.utillinux
];
# TODO if there is plan.user, then use its privkey
makePushService = plan: assert isPushSrc plan; {
path = service-path;
serviceConfig = {
ExecStart = push plan;
Type = "oneshot";
};
startAt = plan.startAt;
};
makePullService = plan: assert isPullDst plan; {
path = service-path;
serviceConfig = {
ExecStart = pull plan;
Type = "oneshot";
};
startAt = plan.startAt;
};
push = plan: let
# We use writeDashBin and return the absolute path so systemd will produce
# nice names in the log, i.e. without the Nix store hash.
out = "${main}/bin/${main.name}";
main = writeDashBin "backup.${plan.name}.push" ''
set -efu
dst=${shell.escape plan.dst.path}
mkdir -m 0700 -p "$dst"
exec flock -n "$dst" ${critical-section}
'';
critical-section = writeDash "backup.${plan.name}.push.critical-section" ''
# TODO check if there is a previous
set -efu
identity=${shell.escape plan.src.host.ssh.privkey.path}
src=${shell.escape plan.src.path}
dst_target=${shell.escape "root@${getFQDN plan.dst.host}"}
dst_path=${shell.escape plan.dst.path}
dst=$dst_target:$dst_path
# Export NOW so runtime of rsync doesn't influence snapshot naming.
export NOW
NOW=$(date +%s)
echo >&2 "update snapshot: current; $src -> $dst"
rsync >&2 \
-aAXF --delete \
-e "ssh -F /dev/null -i $identity" \
--rsync-path ${shell.escape
"mkdir -m 0700 -p ${shell.escape plan.dst.path} && rsync"} \
--link-dest="$dst_path/current" \
"$src/" \
"$dst/.partial"
exec ssh -F /dev/null \
-i "$identity" \
"$dst_target" \
-T \
env NOW="$NOW" /bin/sh < ${remote-snapshot}
EOF
'';
remote-snapshot = writeDash "backup.${plan.name}.push.remote-snapshot" ''
set -efu
dst=${shell.escape plan.dst.path}
if test -e "$dst/current"; then
mv "$dst/current" "$dst/.previous"
fi
mv "$dst/.partial" "$dst/current"
rm -fR "$dst/.previous"
echo >&2
(${(take-snapshots plan).text})
'';
in out;
# TODO admit plan.dst.user and its ssh identity
pull = plan: let
# We use writeDashBin and return the absolute path so systemd will produce
# nice names in the log, i.e. without the Nix store hash.
out = "${main}/bin/${main.name}";
main = writeDashBin "backup.${plan.name}.pull" ''
set -efu
dst=${shell.escape plan.dst.path}
mkdir -m 0700 -p "$dst"
exec flock -n "$dst" ${critical-section}
'';
critical-section = writeDash "backup.${plan.name}.pull.critical-section" ''
# TODO check if there is a previous
set -efu
identity=${shell.escape plan.dst.host.ssh.privkey.path}
src=${shell.escape "root@${getFQDN plan.src.host}:${plan.src.path}"}
dst=${shell.escape plan.dst.path}
# Export NOW so runtime of rsync doesn't influence snapshot naming.
export NOW
NOW=$(date +%s)
echo >&2 "update snapshot: current; $dst <- $src"
mkdir -m 0700 -p ${shell.escape plan.dst.path}
rsync >&2 \
-aAXF --delete \
-e "ssh -F /dev/null -i $identity" \
--link-dest="$dst/current" \
"$src/" \
"$dst/.partial"
mv "$dst/current" "$dst/.previous"
mv "$dst/.partial" "$dst/current"
rm -fR "$dst/.previous"
echo >&2
exec ${take-snapshots plan}
'';
in out;
take-snapshots = plan: writeDash "backup.${plan.name}.take-snapshots" ''
set -efu
NOW=''${NOW-$(date +%s)}
dst=${shell.escape plan.dst.path}
snapshot() {(
: $ns $format $retain
name=$(date --date="@$NOW" +"$format")
if ! test -e "$dst/$ns/$name"; then
echo >&2 "create snapshot: $ns/$name"
mkdir -m 0700 -p "$dst/$ns"
rsync >&2 \
-aAXF --delete \
--link-dest="$dst/current" \
"$dst/current/" \
"$dst/$ns/.partial.$name"
mv "$dst/$ns/.partial.$name" "$dst/$ns/$name"
echo >&2
fi
case $retain in
([0-9]*)
delete_from=$(($retain + 1))
ls -r "$dst/$ns" \
| sed -n "$delete_from,\$p" \
| while read old_name; do
echo >&2 "delete snapshot: $ns/$old_name"
rm -fR "$dst/$ns/$old_name"
done
;;
(ALL)
:
;;
esac
)}
${concatStringsSep "\n" (mapAttrsToList (ns: { format, retain ? null, ... }:
toString (map shell.escape [
"ns=${ns}"
"format=${format}"
"retain=${if retain == null then "ALL" else toString retain}"
"snapshot"
]))
plan.snapshots)}
'';
# TODO getFQDN: admit hosts in other domains
getFQDN = host: "${host.name}.${config.krebs.search-domain}";
writeDash = name: text: pkgs.writeScript name ''
#! ${pkgs.dash}/bin/dash
${text}
'';
writeDashBin = name: text: pkgs.writeTextFile {
executable = true;
destination = "/bin/${name}";
name = name;
text = ''
#! ${pkgs.dash}/bin/dash
${text}
'';
};
in out