1 files changed, 161 insertions, 0 deletions
diff --git a/nixos/modules/services/logging/logstash.nix b/nixos/modules/services/logging/logstash.nix
new file mode 100644
index 00000000000..2f0eea50526
--- /dev/null
+++ b/nixos/modules/services/logging/logstash.nix
@@ -0,0 +1,161 @@
+{ config, pkgs, ... }:
+
+with pkgs.lib;
+
+let
+
+  cfg = config.services.logstash;
+
+  listToConfig = list: "[ " + (concatStringsSep ", " (map exprToConfig list)) + " ]";
+
+  hashToConfig = attrs:
+    let
+      attrNameToConfigList = name:
+        [ (exprToConfig name)  (exprToConfig (getAttr name attrs)) ];
+    in
+      "[ " +
+      (concatStringsSep ", " (map attrNameToConfigList (attrNames attrs))) +
+      " ]";
+
+  valueToConfig = nvpair: let name = nvpair.name; value = nvpair.value; in
+    if (isAttrs value) && ((!(value ? __type)) || value.__type == "repeated")
+      then ''
+        ${name} {
+          ${exprToConfig value}
+        }
+      ''
+      else "${name} => ${exprToConfig value}";
+
+  repeatedAttrsToConfig = values:
+      concatStringsSep "\n" (map valueToConfig values);
+
+  attrsToConfig = attrs:
+    let
+      attrToConfig = name: valueToConfig {
+        inherit name;
+        value = (getAttr name attrs);
+      };
+    in
+      concatStringsSep "\n" (map attrToConfig (attrNames attrs));
+
+  exprToConfig = expr:
+    let
+      isCustomType = expr: (isAttrs expr) && (expr ? __type);
+
+      isFloat = expr: (isCustomType expr) && (expr.__type == "float");
+
+      isHash = expr: (isCustomType expr) && (expr.__type == "hash");
+
+      isRepeatedAttrs = expr: (isCustomType expr) && (expr.__type == "repeated");
+    in
+      if builtins.isBool expr then (if expr then "true" else "false") else
+      if builtins.isString expr then ''"${expr}"'' else
+      if builtins.isInt expr then toString expr else
+      if isFloat expr then expr.value else
+      if isList expr then listToConfig expr else
+      if isHash expr then hashToConfig expr.value else
+      if isRepeatedAttrs expr then repeatedAttrsToConfig expr.values
+      else attrsToConfig expr;
+
+  mergeConfigs = configs:
+    let
+      op = attrs: newAttrs:
+        let
+          isRepeated = newAttrs ? __type && newAttrs.__type == "repeated";
+        in {
+            values = attrs.values ++ (if isRepeated then newAttrs.values else
+              map (name: { inherit name; value = getAttr name newAttrs; })
+              (attrNames newAttrs));
+          };
+    in (foldl op { values = []; } configs) // { __type = "repeated"; };
+
+in
+
+{
+  ###### interface
+
+  options = {
+    services.logstash = {
+      enable = mkOption {
+        default = false;
+        description = ''
+          Enable logstash.
+        '';
+      };
+
+      inputConfig = mkOption {
+        default = {};
+        description = ''
+          An attribute set (or an expression generated by mkNameValuePairs)
+          representing a logstash configuration's input section.
+          Logstash configs are name-value pairs, where values can be bools,
+          strings, numbers, arrays, hashes, or other name-value pairs,
+          and names are strings that can be repeated. Name-value pairs with no
+          repeats are represented by attr sets. Bools, strings, ints, and
+          arrays are mapped directly. Name-value pairs with repeats can be
+          generated by the config.lib.logstash.mkNameValuePairs function, which
+          takes a list of attrsets and combines them while preserving attribute
+          name duplicates if they occur. Similarly, there are the mkFloat and
+          mkHash functions, which take a string representation of a float and an
+          attrset, respectively.
+        '';
+        merge = mergeConfigs;
+      };
+
+      filterConfig = mkOption {
+        default = {};
+        description = ''
+          An attribute set (or an expression generated by mkNameValuePairs)
+          representing a logstash configuration's filter section.
+          See inputConfig description for details.
+        '';
+        merge = mergeConfigs;
+      };
+
+      outputConfig = mkOption {
+        default = {};
+        description = ''
+          An attribute set (or an expression generated by mkNameValuePairs)
+          representing a logstash configuration's output section.
+          See inputConfig description for details.
+        '';
+        merge = mergeConfigs;
+      };
+    };
+  };
+
+
+  ###### implementation
+
+  config = mkMerge [ {
+    lib.logstash = {
+      mkFloat = stringRep: { __type = "float"; value = stringRep; };
+
+      mkHash = attrs: { __type = "hash"; value = attrs; };
+
+      mkNameValuePairs = mergeConfigs;
+    };
+  } ( mkIf cfg.enable {
+    systemd.services.logstash = with pkgs; {
+      description = "Logstash daemon";
+
+      wantedBy = [ "multi-user.target" ];
+
+      path = [ jre ];
+
+      script = "cd /tmp && exec java -jar ${logstash} agent -f ${writeText "logstash.conf" ''
+        input {
+          ${exprToConfig cfg.inputConfig}
+        }
+
+        filter {
+          ${exprToConfig cfg.filterConfig}
+        }
+
+        output {
+          ${exprToConfig cfg.outputConfig}
+        }
+      ''} &> /var/log/logstash.log";
+    };
+  })];
+}