nixos/prometheus: abstract over optional option creation

nixos/modules/services/monitoring/prometheus/default.nix

@@ -120,41 +120,37 @@ let
       map (filterAttrsListRecursive pred) x
     else x;
 
-  promTypes.globalConfig = types.submodule {
-    options = {
-      scrape_interval = mkOption {
-        type = types.nullOr types.str;
-        default = null;
-        description = ''
-          How frequently to scrape targets by default.
-        '';
-      };
+  mkDefOpt = type : defaultStr : description : mkOpt type (description + ''
 
-      scrape_timeout = mkOption {
-        type = types.nullOr types.str;
-        default = null;
-        description = ''
-          How long until a scrape request times out.
-        '';
-      };
+    Defaults to <literal>${defaultStr}</literal> in prometheus
+    when set to <literal>null</literal>.
+  '');
 
-      evaluation_interval = mkOption {
-        type = types.nullOr types.str;
-        default = null;
-        description = ''
-          How frequently to evaluate rules by default.
-        '';
-      };
+  mkOpt = type : description : mkOption {
+    type = types.nullOr type;
+    default = null;
+    inherit description;
+  };
 
-      external_labels = mkOption {
-        type = types.nullOr (types.attrsOf types.str);
-        description = ''
-          The labels to add to any time series or alerts when
-          communicating with external systems (federation, remote
-          storage, Alertmanager).
-        '';
-        default = null;
-      };
+  promTypes.globalConfig = types.submodule {
+    options = {
+      scrape_interval = mkDefOpt types.str "1m" ''
+        How frequently to scrape targets by default.
+      '';
+
+      scrape_timeout = mkDefOpt types.str "10s" ''
+        How long until a scrape request times out.
+      '';
+
+      evaluation_interval = mkDefOpt types.str "1m" ''
+        How frequently to evaluate rules by default.
+      '';
+
+      external_labels = mkOpt (types.attrsOf types.str) ''
+        The labels to add to any time series or alerts when
+        communicating with external systems (federation, remote
+        storage, Alertmanager).
+      '';
     };
   };
 
@@ -166,137 +162,94 @@ let
           The job name assigned to scraped metrics by default.
         '';
       };
-      scrape_interval = mkOption {
-        type = types.nullOr types.str;
-        default = null;
-        description = ''
-          How frequently to scrape targets from this job. Defaults to the
-          globally configured default.
-        '';
-      };
-      scrape_timeout = mkOption {
-        type = types.nullOr types.str;
-        default = null;
-        description = ''
-          Per-target timeout when scraping this job. Defaults to the
-          globally configured default.
-        '';
-      };
-      metrics_path = mkOption {
-        type = types.nullOr types.str;
-        default = null;
-        description = ''
-          The HTTP resource path on which to fetch metrics from targets.
-        '';
-      };
-      honor_labels = mkOption {
-        type = types.nullOr types.bool;
-        default = null;
-        description = ''
-          Controls how Prometheus handles conflicts between labels
-          that are already present in scraped data and labels that
-          Prometheus would attach server-side ("job" and "instance"
-          labels, manually configured target labels, and labels
-          generated by service discovery implementations).
+      scrape_interval = mkOpt types.str ''
+        How frequently to scrape targets from this job. Defaults to the
+        globally configured default.
+      '';
+
+      scrape_timeout = mkOpt types.str ''
+        Per-target timeout when scraping this job. Defaults to the
+        globally configured default.
+      '';
+
+      metrics_path = mkDefOpt types.str "/metrics" ''
+        The HTTP resource path on which to fetch metrics from targets.
+      '';
+
+      honor_labels = mkDefOpt types.bool "false" ''
+        Controls how Prometheus handles conflicts between labels
+        that are already present in scraped data and labels that
+        Prometheus would attach server-side ("job" and "instance"
+        labels, manually configured target labels, and labels
+        generated by service discovery implementations).
+
+        If honor_labels is set to "true", label conflicts are
+        resolved by keeping label values from the scraped data and
+        ignoring the conflicting server-side labels.
+
+        If honor_labels is set to "false", label conflicts are
+        resolved by renaming conflicting labels in the scraped data
+        to "exported_&lt;original-label&gt;" (for example
+        "exported_instance", "exported_job") and then attaching
+        server-side labels. This is useful for use cases such as
+        federation, where all labels specified in the target should
+        be preserved.
+      '';
+
+      scheme = mkDefOpt (types.enum ["http" "https"]) "http" ''
+        The URL scheme with which to fetch metrics from targets.
+      '';
+
+      params = mkOpt (types.attrsOf (types.listOf types.str)) ''
+        Optional HTTP URL parameters.
+      '';
+
+      basic_auth = mkOpt (types.submodule {
+        options = {
+          username = mkOption {
+            type = types.str;
+            description = ''
+              HTTP username
+            '';
+          };
+          password = mkOption {
+            type = types.str;
+            description = ''
+              HTTP password
+            '';
+          };
+        };
+      }) ''
+        Optional http login credentials for metrics scraping.
+      '';
 
-          If honor_labels is set to "true", label conflicts are
-          resolved by keeping label values from the scraped data and
-          ignoring the conflicting server-side labels.
+      tls_config = mkOpt promTypes.tls_config ''
+        Configures the scrape request's TLS settings.
+      '';
 
-          If honor_labels is set to "false", label conflicts are
-          resolved by renaming conflicting labels in the scraped data
-          to "exported_&lt;original-label&gt;" (for example
-          "exported_instance", "exported_job") and then attaching
-          server-side labels. This is useful for use cases such as
-          federation, where all labels specified in the target should
-          be preserved.
-        '';
-      };
-      scheme = mkOption {
-        type = types.nullOr (types.enum ["http" "https"]);
-        default = null;
-        description = ''
-          The URL scheme with which to fetch metrics from targets.
-        '';
-      };
-      params = mkOption {
-        type = types.nullOr (types.attrsOf (types.listOf types.str));
-        default = null;
-        description = ''
-          Optional HTTP URL parameters.
-        '';
-      };
-      basic_auth = mkOption {
-        type = types.nullOr (types.submodule {
-          options = {
-            username = mkOption {
-              type = types.str;
-              description = ''
-                HTTP username
-              '';
-            };
-            password = mkOption {
-              type = types.str;
-              description = ''
-                HTTP password
-              '';
-            };
-          };
-        });
-        default = null;
-        description = ''
-          Optional http login credentials for metrics scraping.
-        '';
-      };
-      tls_config = mkOption {
-        type = types.nullOr promTypes.tls_config;
-        default = null;
-        description = ''
-          Configures the scrape request's TLS settings.
-        '';
-      };
-      dns_sd_configs = mkOption {
-        type = types.nullOr (types.listOf promTypes.dns_sd_config);
-        default = null;
-        description = ''
-          List of DNS service discovery configurations.
-        '';
-      };
-      consul_sd_configs = mkOption {
-        type = types.nullOr (types.listOf promTypes.consul_sd_config);
-        default = null;
-        description = ''
-          List of Consul service discovery configurations.
-        '';
-      };
-      file_sd_configs = mkOption {
-        type = types.nullOr (types.listOf promTypes.file_sd_config);
-        default = null;
-        description = ''
-          List of file service discovery configurations.
-        '';
-      };
-      static_configs = mkOption {
-        type = types.nullOr (types.listOf promTypes.static_config);
-        default = null;
-        description = ''
-          List of labeled target groups for this job.
-        '';
-      };
-      ec2_sd_configs = mkOption {
-        type = types.nullOr (types.listOf promTypes.ec2_sd_config);
-        default = null;
-        description = ''
-          List of EC2 service discovery configurations.
-        '';
-      };
-      relabel_configs = mkOption {
-        type = types.nullOr (types.listOf promTypes.relabel_config);
-        default = null;
-        description = ''
-          List of relabel configurations.
-        '';
-      };
+      dns_sd_configs = mkOpt (types.listOf promTypes.dns_sd_config) ''
+        List of DNS service discovery configurations.
+      '';
+
+      consul_sd_configs = mkOpt (types.listOf promTypes.consul_sd_config) ''
+        List of Consul service discovery configurations.
+      '';
+
+      file_sd_configs = mkOpt (types.listOf promTypes.file_sd_config) ''
+        List of file service discovery configurations.
+      '';
+
+      static_configs = mkOpt (types.listOf promTypes.static_config) ''
+        List of labeled target groups for this job.
+      '';
+
+      ec2_sd_configs = mkOpt (types.listOf promTypes.ec2_sd_config) ''
+        List of EC2 service discovery configurations.
+      '';
+
+      relabel_configs = mkOpt (types.listOf promTypes.relabel_config) ''
+        List of relabel configurations.
+      '';
     };
   };
 
@@ -326,66 +279,41 @@ let
           The AWS Region.
         '';
       };
-      endpoint = mkOption {
-        type = types.nullOr types.str;
-        default = null;
-        description = ''
-          Custom endpoint to be used.
-        '';
-      };
-      access_key = mkOption {
-        type = types.nullOr types.str;
-        default = null;
-        description = ''
-          The AWS API key id. If blank, the environment variable
-          <literal>AWS_ACCESS_KEY_ID</literal> is used.
-        '';
-      };
-      secret_key = mkOption {
-        type = types.nullOr types.str;
-        default = null;
-        description = ''
-          The AWS API key secret. If blank, the environment variable
-           <literal>AWS_SECRET_ACCESS_KEY</literal> is used.
-        '';
-      };
-      profile = mkOption {
-        type = types.nullOr types.str;
-        default = null;
-        description = ''
-          Named AWS profile used to connect to the API.
-        '';
-      };
-      role_arn = mkOption {
-        type = types.nullOr types.str;
-        default = null;
-        description = ''
-          AWS Role ARN, an alternative to using AWS API keys.
-        '';
-      };
-      refresh_interval = mkOption {
-        type = types.nullOr types.str;
-        default = null;
-        description = ''
-          Refresh interval to re-read the instance list.
-        '';
-      };
-      port = mkOption {
-        type = types.nullOr types.int;
-        default = null;
-        description = ''
-          The port to scrape metrics from. If using the public IP
-          address, this must instead be specified in the relabeling
-          rule.
-        '';
-      };
-      filters = mkOption {
-        type = types.nullOr (types.listOf promTypes.filter);
-        default = null;
-        description = ''
-          Filters can be used optionally to filter the instance list by other criteria.
-        '';
-      };
+      endpoint = mkOpt types.str ''
+        Custom endpoint to be used.
+      '';
+
+      access_key = mkOpt types.str ''
+        The AWS API key id. If blank, the environment variable
+        <literal>AWS_ACCESS_KEY_ID</literal> is used.
+      '';
+
+      secret_key = mkOpt types.str ''
+        The AWS API key secret. If blank, the environment variable
+         <literal>AWS_SECRET_ACCESS_KEY</literal> is used.
+      '';
+
+      profile = mkOpt  types.str ''
+        Named AWS profile used to connect to the API.
+      '';
+
+      role_arn = mkOpt types.str ''
+        AWS Role ARN, an alternative to using AWS API keys.
+      '';
+
+      refresh_interval = mkDefOpt types.str "60s" ''
+        Refresh interval to re-read the instance list.
+      '';
+
+      port = mkDefOpt types.int "80" ''
+        The port to scrape metrics from. If using the public IP
+        address, this must instead be specified in the relabeling
+        rule.
+      '';
+
+      filters = mkOpt (types.listOf promTypes.filter) ''
+        Filters can be used optionally to filter the instance list by other criteria.
+      '';
     };
   };
 
@@ -398,6 +326,7 @@ let
           for the available filters.
         '';
       };
+
       value = mkOption {
         type = types.listOf types.str;
         default = [];
@@ -416,58 +345,36 @@ let
           A list of DNS SRV record names to be queried.
         '';
       };
-      refresh_interval = mkOption {
-        type = types.nullOr types.str;
-        default = null;
-        description = ''
-          The time after which the provided names are refreshed.
-        '';
-      };
+
+      refresh_interval = mkDefOpt types.str "30s" ''
+        The time after which the provided names are refreshed.
+      '';
     };
   };
 
   promTypes.consul_sd_config = types.submodule {
     options = {
-      server = mkOption {
-        type = types.nullOr types.str;
-        default = null;
-        description = "Consul server to query.";
-      };
-      token = mkOption {
-        type = types.nullOr types.str;
-        description = "Consul token";
-      };
-      datacenter = mkOption {
-        type = types.nullOr types.str;
-        description = "Consul datacenter";
-      };
-      scheme = mkOption {
-        type = types.nullOr types.str;
-        description = "Consul scheme";
-      };
-      username = mkOption {
-        type = types.nullOr types.str;
-        description = "Consul username";
-      };
-      password = mkOption {
-        type = types.nullOr types.str;
-        description = "Consul password";
-      };
+      server = mkDefOpt types.str "localhost:8500" ''
+        Consul server to query.
+      '';
 
-      services = mkOption {
-        type = types.nullOr (types.listOf types.str);
-        default = null;
-        description = ''
-          A list of services for which targets are retrieved.
-        '';
-      };
-      tag_separator = mkOption {
-        type = types.nullOr types.str;
-        default = null;
-        description = ''
-          The string by which Consul tags are joined into the tag label.
-        '';
-      };
+      token = mkOpt types.str "Consul token";
+
+      datacenter = mkOpt types.str "Consul datacenter";
+
+      scheme = mkDefOpt types.str "http" "Consul scheme";
+
+      username = mkOpt types.str "Consul username";
+
+      password = mkOpt types.str "Consul password";
+
+      services = mkOpt (types.listOf types.str) ''
+        A list of services for which targets are retrieved.
+      '';
+
+      tag_separator = mkDefOpt types.str "," ''
+        The string by which Consul tags are joined into the tag label.
+      '';
     };
   };
 
@@ -481,105 +388,68 @@ let
           and formats.
         '';
       };
-      refresh_interval = mkOption {
-        type = types.nullOr types.str;
-        default = null;
-        description = ''
-          Refresh interval to re-read the files.
-        '';
-      };
+
+      refresh_interval = mkDefOpt types.str "5m" ''
+        Refresh interval to re-read the files.
+      '';
     };
   };
 
   promTypes.relabel_config = types.submodule {
     options = {
-      source_labels = mkOption {
-        type = types.nullOr (types.listOf str);
-        default = null;
-        description = ''
-          The source labels select values from existing labels. Their content
-          is concatenated using the configured separator and matched against
-          the configured regular expression.
-        '';
-      };
-      separator = mkOption {
-        type = types.nullOr types.str;
-        default = null;
-        description = ''
-          Separator placed between concatenated source label values.
-        '';
-      };
-      target_label = mkOption {
-        type = types.nullOr types.str;
-        default = null;
-        description = ''
-          Label to which the resulting value is written in a replace action.
-          It is mandatory for replace actions.
-        '';
-      };
-      regex = mkOption {
-        type = types.nullOr types.str;
-        default = null;
-        description = ''
-          Regular expression against which the extracted value is matched.
-        '';
-      };
-      replacement = mkOption {
-        type = types.nullOr types.str;
-        default = null;
-        description = ''
-          Replacement value against which a regex replace is performed if the
-          regular expression matches.
-        '';
-      };
-      action = mkOption {
-        type = types.nullOr (types.enum ["replace" "keep" "drop"]);
-        default = null;
-        description = ''
-          Action to perform based on regex matching.
-        '';
-      };
+      source_labels = mkOpt (types.listOf types.str) ''
+        The source labels select values from existing labels. Their content
+        is concatenated using the configured separator and matched against
+        the configured regular expression.
+      '';
+
+      separator = mkDefOpt types.str ";" ''
+        Separator placed between concatenated source label values.
+      '';
+
+      target_label = mkOpt types.str ''
+        Label to which the resulting value is written in a replace action.
+        It is mandatory for replace actions.
+      '';
+
+      regex = mkDefOpt types.str "(.*)" ''
+        Regular expression against which the extracted value is matched.
+      '';
+
+      replacement = mkDefOpt types.str "$1" ''
+        Replacement value against which a regex replace is performed if the
+        regular expression matches.
+      '';
+
+      action = mkDefOpt (types.enum ["replace" "keep" "drop"]) "replace" ''
+        Action to perform based on regex matching.
+      '';
+
     };
   };
 
   promTypes.tls_config = types.submodule {
     options = {
-      ca_file = mkOption {
-        type = types.nullOr types.str;
-        default = null;
-        description = ''
-          CA certificate to validate API server certificate with.
-        '';
-      };
-      cert_file = mkOption {
-        type = types.nullOr types.str;
-        default = null;
-        description = ''
-          Certificate file for client cert authentication to the server.
-        '';
-      };
-      key_file = mkOption {
-        type = types.nullOr types.str;
-        default = null;
-        description = ''
-          Key file for client cert authentication to the server.
-        '';
-      };
-      server_name = mkOption {
-        type = types.nullOr types.str;
-        default = null;
-        description = ''
-          ServerName extension to indicate the name of the server.
-          http://tools.ietf.org/html/rfc4366#section-3.1
-        '';
-      };
-      insecure_skip_verify = mkOption {
-        type = types.bool;
-        default = false;
-        description = ''
-          Disable validation of the server certificate.
-        '';
-      };
+      ca_file = mkOpt types.str ''
+        CA certificate to validate API server certificate with.
+      '';
+
+      cert_file = mkOpt types.str ''
+        Certificate file for client cert authentication to the server.
+      '';
+
+      key_file = mkOpt types.str ''
+        Key file for client cert authentication to the server.
+      '';
+
+      server_name = mkOpt types.str ''
+        ServerName extension to indicate the name of the server.
+        http://tools.ietf.org/html/rfc4366#section-3.1
+      '';
+
+      insecure_skip_verify = mkOpt types.bool ''
+        Disable validation of the server certificate.
+      '';
     };
   };