Merge pull request #32914 from Infinisil/znapzendzetup

znapzend service: stateless setup

nixos/modules/services/backup/znapzend.nix

···
 { config, lib, pkgs, ... }:
 
 with lib;
+with types;
 
 let
+
+  # Converts a plan like
+  #   { "1d" = "1h"; "1w" = "1d"; }
+  # into
+  #   "1d=>1h,1w=>1d"
+  attrToPlan = attrs: concatStringsSep "," (builtins.attrValues (
+    mapAttrs (n: v: "${n}=>${v}") attrs));
+
+  planDescription = ''
+      The znapzend backup plan to use for the source.
+    </para>
+    <para>
+      The plan specifies how often to backup and for how long to keep the
+      backups. It consists of a series of retention periodes to interval
+      associations:
+    </para>
+    <para>
+      <literal>
+        retA=>intA,retB=>intB,...
+      </literal>
+    </para>
+    <para>
+    Both intervals and retention periods are expressed in standard units
+    of time or multiples of them. You can use both the full name or a
+    shortcut according to the following listing:
+    </para>
+    <para>
+      <literal>
+        second|sec|s, minute|min, hour|h, day|d, week|w, month|mon|m, year|y
+      </literal>
+    </para>
+    <para>
+      See <citerefentry><refentrytitle>znapzendzetup</refentrytitle><manvolnum>1</manvolnum></citerefentry> for more info.
+  '';
+  planExample = "1h=>10min,1d=>1h,1w=>1d,1m=>1w,1y=>1m";
+
+  # A type for a string of the form number{b|k|M|G}
+  mbufferSizeType = str // {
+    check = x: str.check x && builtins.isList (builtins.match "^[0-9]+[bkMG]$" x);
+    description = "string of the form number{b|k|M|G}";
+  };
+
+  # Type for a string that must contain certain other strings (the list parameter).
+  # Note that these would need regex escaping.
+  stringContainingStrings = list: let
+    matching = s: map (str: builtins.match ".*${str}.*" s) list;
+  in str // {
+    check = x: str.check x && all isList (matching x);
+    description = "string containing all of the characters ${concatStringsSep ", " list}";
+  };
+
+  timestampType = stringContainingStrings [ "%Y" "%m" "%d" "%H" "%M" "%S" ];
+
+  destType = srcConfig: submodule ({ name, ... }: {
+    options = {
+
+      label = mkOption {
+        type = str;
+        description = "Label for this destination. Defaults to the attribute name.";
+      };
+
+      plan = mkOption {
+        type = str;
+        description = planDescription;
+        example = planExample;
+      };
+
+      dataset = mkOption {
+        type = str;
+        description = "Dataset name to send snapshots to.";
+        example = "tank/main";
+      };
+
+      host = mkOption {
+        type = nullOr str;
+        description = ''
+          Host to use for the destination dataset. Can be prefixed with
+          <literal>user@</literal> to specify the ssh user.
+        '';
+        default = null;
+        example = "[e-mail]";
+      };
+
+      presend = mkOption {
+        type = nullOr str;
+        description = ''
+          Command to run before sending the snapshot to the destination.
+          Intended to run a remote script via <command>ssh</command> on the
+          destination, e.g. to bring up a backup disk or server or to put a
+          zpool online/offline. See also <option>postsend</option>.
+        '';
+        default = null;
+        example = "ssh root@bserv zpool import -Nf tank";
+      };
+
+      postsend = mkOption {
+        type = nullOr str;
+        description = ''
+          Command to run after sending the snapshot to the destination.
+          Intended to run a remote script via <command>ssh</command> on the
+          destination, e.g. to bring up a backup disk or server or to put a
+          zpool online/offline. See also <option>presend</option>.
+        '';
+        default = null;
+        example = "ssh root@bserv zpool export tank";
+      };
+    };
+
+    config = {
+      label = mkDefault name;
+      plan = mkDefault srcConfig.plan;
+    };
+  });
+
+
+
+  srcType = submodule ({ name, config, ... }: {
+    options = {
+
+      enable = mkOption {
+        type = bool;
+        description = "Whether to enable this source.";
+        default = true;
+      };
+
+      recursive = mkOption {
+        type = bool;
+        description = "Whether to do recursive snapshots.";
+        default = false;
+      };
+
+      mbuffer = {
+        enable = mkOption {
+          type = bool;
+          description = "Whether to use <command>mbuffer</command>.";
+          default = false;
+        };
+
+        port = mkOption {
+          type = nullOr ints.u16;
+          description = ''
+              Port to use for <command>mbuffer</command>.
+            </para>
+            <para>
+              If this is null, it will run <command>mbuffer</command> through
+              ssh.
+            </para>
+            <para>
+              If this is not null, it will run <command>mbuffer</command>
+              directly through TCP, which is not encrypted but faster. In that
+              case the given port needs to be open on the destination host.
+          '';
+          default = null;
+        };
+
+        size = mkOption {
+          type = mbufferSizeType;
+          description = ''
+            The size for <command>mbuffer</command>.
+            Supports the units b, k, M, G.
+          '';
+          default = "1G";
+          example = "128M";
+        };
+      };
+
+      presnap = mkOption {
+        type = nullOr str;
+        description = ''
+          Command to run before snapshots are taken on the source dataset,
+          e.g. for database locking/flushing. See also
+          <option>postsnap</option>.
+        '';
+        default = null;
+        example = literalExample ''
+          ''${pkgs.mariadb}/bin/mysql -e "set autocommit=0;flush tables with read lock;\\! ''${pkgs.coreutils}/bin/sleep 600" &  ''${pkgs.coreutils}/bin/echo $! > /tmp/mariadblock.pid ; sleep 10
+        '';
+      };
+
+      postsnap = mkOption {
+        type = nullOr str;
+        description = ''
+          Command to run after snapshots are taken on the source dataset,
+          e.g. for database unlocking. See also <option>presnap</option>.
+        '';
+        default = null;
+        example = literalExample ''
+          ''${pkgs.coreutils}/bin/kill `''${pkgs.coreutils}/bin/cat /tmp/mariadblock.pid`;''${pkgs.coreutils}/bin/rm /tmp/mariadblock.pid
+        '';
+      };
+
+      timestampFormat = mkOption {
+        type = timestampType;
+        description = ''
+          The timestamp format to use for constructing snapshot names.
+          The syntax is <literal>strftime</literal>-like. The string must
+          consist of the mandatory <literal>%Y %m %d %H %M %S</literal>.
+          Optionally  <literal>- _ . :</literal>  characters as well as any
+          alphanumeric character are allowed. If suffixed by a
+          <literal>Z</literal>, times will be in UTC.
+        '';
+        default = "%Y-%m-%d-%H%M%S";
+        example = "znapzend-%m.%d.%Y-%H%M%SZ";
+      };
+
+      sendDelay = mkOption {
+        type = int;
+        description = ''
+          Specify delay (in seconds) before sending snaps to the destination.
+          May be useful if you want to control sending time.
+        '';
+        default = 0;
+        example = 60;
+      };
+
+      plan = mkOption {
+        type = str;
+        description = planDescription;
+        example = planExample;
+      };
+
+      dataset = mkOption {
+        type = str;
+        description = "The dataset to use for this source.";
+        example = "tank/home";
+      };
+
+      destinations = mkOption {
+        type = loaOf (destType config);
+        description = "Additional destinations.";
+        default = {};
+        example = literalExample ''
+          {
+            local = {
+              dataset = "btank/backup";
+              presend = "zpool import -N btank";
+              postsend = "zpool export btank";
+            };
+            remote = {
+              host = "[e-mail]";
+              dataset = "tank/john";
+            };
+          };
+        '';
+      };
+    };
+
+    config = {
+      dataset = mkDefault name;
+    };
+
+  });
+
+  ### Generating the configuration from here
+
   cfg = config.services.znapzend;
+
+  onOff = b: if b then "on" else "off";
+  nullOff = b: if isNull b then "off" else toString b;
+  stripSlashes = replaceStrings [ "/" ] [ "." ];
+
+  attrsToFile = config: concatStringsSep "\n" (builtins.attrValues (
+    mapAttrs (n: v: "${n}=${v}") config));
+
+  mkDestAttrs = dst: with dst;
+    mapAttrs' (n: v: nameValuePair "dst_${label}${n}" v) ({
+      "" = optionalString (! isNull host) "${host}:" + dataset;
+      _plan = plan;
+    } // optionalAttrs (presend != null) {
+      _precmd = presend;
+    } // optionalAttrs (postsend != null) {
+      _pstcmd = postsend;
+    });
+
+  mkSrcAttrs = srcCfg: with srcCfg; {
+    enabled = onOff enable;
+    mbuffer = with mbuffer; if enable then "${pkgs.mbuffer}/bin/mbuffer"
+        + optionalString (port != null) ":${toString port}" else "off";
+    mbuffer_size = mbuffer.size;
+    post_znap_cmd = nullOff postsnap;
+    pre_znap_cmd = nullOff presnap;
+    recursive = onOff recursive;
+    src = dataset;
+    src_plan = plan;
+    tsformat = timestampFormat;
+    zend_delay = toString sendDelay;
+  } // fold (a: b: a // b) {} (
+    map mkDestAttrs (builtins.attrValues destinations)
+  );
+
+  files = mapAttrs' (n: srcCfg: let
+    fileText = attrsToFile (mkSrcAttrs srcCfg);
+  in {
+    name = srcCfg.dataset;
+    value = pkgs.writeText (stripSlashes srcCfg.dataset) fileText;
+  }) cfg.zetup;
+
 in
 {
   options = {
     services.znapzend = {
-      enable = mkEnableOption "ZnapZend daemon";
+      enable = mkEnableOption "ZnapZend ZFS backup daemon";
 
       logLevel = mkOption {
         default = "debug";
         example = "warning";
-        type = lib.types.enum ["debug" "info" "warning" "err" "alert"];
-        description = "The log level when logging to file. Any of debug, info, warning, err, alert. Default in daemonized form is debug.";
+        type = enum ["debug" "info" "warning" "err" "alert"];
+        description = ''
+          The log level when logging to file. Any of debug, info, warning, err,
+          alert. Default in daemonized form is debug.
+        '';
       };
 
       logTo = mkOption {
-        type = types.str;
+        type = str;
         default = "syslog::daemon";
         example = "/var/log/znapzend.log";
-        description = "Where to log to (syslog::&lt;facility&gt; or &lt;filepath&gt;).";
+        description = ''
+          Where to log to (syslog::&lt;facility&gt; or &lt;filepath&gt;).
+        '';
       };
 
       noDestroy = mkOption {
-        type = types.bool;
+        type = bool;
         default = false;
         description = "Does all changes to the filesystem except destroy.";
       };
 
       autoCreation = mkOption {
-        type = types.bool;
+        type = bool;
         default = false;
-        description = "Automatically create the dataset on dest if it does not exists.";
+        description = "Automatically create the destination dataset if it does not exists.";
+      };
+
+      zetup = mkOption {
+        type = loaOf srcType;
+        description = "Znapzend configuration.";
+        default = {};
+        example = literalExample ''
+          {
+            "tank/home" = {
+              # Make snapshots of tank/home every hour, keep those for 1 day,
+              # keep every days snapshot for 1 month, etc.
+              plan = "1d=>1h,1m=>1d,1y=>1m";
+              recursive = true;
+              # Send all those snapshots to [e-mail]:rtank/john as well
+              destinations.remote = {
+                host = "[e-mail]";
+                dataset = "rtank/john";
+              };
+            };
+          };
+        '';
+      };
+
+      pure = mkOption {
+        type = bool;
+        description = ''
+          Do not persist any stateful znapzend setups. If this option is
+          enabled, your previously set znapzend setups will be cleared and only
+          the ones defined with this module will be applied.
+        '';
+        default = false;
       };
     };
   };
···
 
         path = with pkgs; [ zfs mbuffer openssh ];
 
+        preStart = optionalString cfg.pure ''
+          echo Resetting znapzend zetups
+          ${pkgs.znapzend}/bin/znapzendzetup list \
+            | grep -oP '(?<=\*\*\* backup plan: ).*(?= \*\*\*)' \
+            | xargs ${pkgs.znapzend}/bin/znapzendzetup delete
+        '' + concatStringsSep "\n" (mapAttrsToList (dataset: config: ''
+          echo Importing znapzend zetup ${config} for dataset ${dataset}
+          ${pkgs.znapzend}/bin/znapzendzetup import --write ${dataset} ${config}
+        '') files);
+
         serviceConfig = {
-          ExecStart = "${pkgs.znapzend}/bin/znapzend --logto=${cfg.logTo} --loglevel=${cfg.logLevel} ${optionalString cfg.noDestroy "--nodestroy"} ${optionalString cfg.autoCreation "--autoCreation"}";
+          ExecStart = let
+            args = concatStringsSep " " [
+              "--logto=${cfg.logTo}"
+              "--loglevel=${cfg.logLevel}"
+              (optionalString cfg.noDestroy "--nodestroy")
+              (optionalString cfg.autoCreation "--autoCreation")
+            ]; in "${pkgs.znapzend}/bin/znapzend ${args}";
           ExecReload = "${pkgs.coreutils}/bin/kill -HUP $MAINPID";
           Restart = "on-failure";
         };
       };
     };
   };
+
+  meta.maintainers = with maintainers; [ infinisil ];
 }