modules/ascension: init

modules/ascensions/default.nix

@@ -0,0 +1,125 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+  ascensionsDir = "/var/lib/ascensions";
+
+  ascensionType = { name, ... }: {
+    options = {
+      incantations = mkOption {
+        type = with types; functionTo (listOf package);
+        default = [];
+      };
+      distributed = mkOption {
+        type = types.bool;
+        default = false;
+        description = "Whether to perform a distributed ascension using Consul KV.";
+      };
+      requiredBy = mkOption {
+        type = with types; listOf str;
+        default = [ "${name}.service" ];
+        description = "Services that require this ascension.";
+      };
+      before = mkOption {
+        type = with types; listOf str;
+        default = [];
+        description = "Run the ascension before these services.";
+      };
+      after = mkOption {
+        type = with types; listOf str;
+        default = [];
+        description = "Run the ascension after these services.";
+      };
+    };
+  };
+
+  runIncantations = f: with pkgs; f rec {
+    execShellWith = extraPackages: script: writeShellScript "incantation" ''
+      export PATH='${makeBinPath ([ coreutils ] ++ extraPackages)}'
+      ${script}
+    '';
+
+    execShell = execShellWith [];
+
+    multiple = incantations: execShell (concatStringsSep " && " incantations);
+
+    move = from: to: execShell ''
+      test -e ${escapeShellArg from} && rm -rf ${escapeShellArg to}
+      mkdir -p "$(dirname ${escapeShellArg to})"
+      mv ${escapeShellArgs [ from to ]}
+    '';
+
+    chmod = mode: target: "chmod -R ${escapeShellArgs [ mode target ]}";
+  };
+
+  consul = config.services.consul.package;
+in
+
+{
+  options.system.ascensions = mkOption {
+    type = with types; attrsOf (submodule ascensionType);
+    default = {};
+  };
+
+  config = {
+    systemd = {
+      tmpfiles.rules = [
+        "d ${ascensionsDir} 0755 root root - -"
+      ];
+
+      services = mapAttrs' (name: asc: {
+        name = "ascend-${name}";
+        value = let
+          incantations = runIncantations asc.incantations;
+          targetLevel = toString (length incantations);
+        in {
+          description = "Ascension for ${name}";
+          inherit (asc) requiredBy before;
+          after = asc.after ++ (lib.optional asc.distributed "consul.service");
+          serviceConfig.Type = "oneshot";
+          distributed.enable = asc.distributed;
+          script = ''
+            incantations=(${concatStringsSep " " incantations})
+            ${if asc.distributed then /*bash*/ ''
+              getLevel() {
+                ${consul}/bin/consul kv get 'ascensions/${name}/currentLevel'
+              }
+              setLevel() {
+                ${consul}/bin/consul kv put 'ascensions/${name}/currentLevel' "$1" >/dev/null
+              }
+              isEmpty() {
+                ! getLevel >/dev/null 2>/dev/null
+              }
+            '' else /*bash*/ ''
+              levelFile='${ascensionsDir}/${name}'
+              getLevel() {
+                echo "$(<"$levelFile")"
+              }
+              setLevel() {
+                echo "$1" > "$levelFile"
+              }
+              isEmpty() {
+                [[ ! -e "$levelFile" ]]
+              }
+            ''
+            }
+            if isEmpty; then
+              setLevel '${targetLevel}'
+              echo Initializing at level ${targetLevel}
+              exit 0
+            fi
+            cur=$(getLevel)
+            echo Current level: $cur
+            for lvl in $(seq $(($cur+1)) ${targetLevel}); do
+              echo Running incantation for level $lvl...
+              ''${incantations[$((lvl-1))]}
+              setLevel "$lvl"
+            done
+            echo All incantations complete, ascended to level $(getLevel)
+          '';
+        };
+      }) config.system.ascensions;
+    };
+  };
+}

modules/part.nix

@@ -7,6 +7,7 @@ in
 {
   flake.nixosModules = with config.flake.nixosModules; {
     autopatch = ./autopatch;
+    ascensions = ./ascensions;
     consul-distributed-services = ./consul-distributed-services;
     consul-service-registry = ./consul-service-registry;
     deploy-rs-receiver = ./deploy-rs-receiver;
@@ -45,6 +46,7 @@ in
 
     serverBase = group [
       machineBase
+      ascensions
       consul-distributed-services
       consul-service-registry
       deploy-rs-receiver