nixos/prometheus-json-exporter: update modules & tests, add release notes

nixos/doc/manual/release-notes/rl-2103.xml

@@ -295,6 +295,32 @@
        Based on <xref linkend="opt-system.stateVersion" />, existing installations will continue to work.
      </para>
    </listitem>
+   <listitem>
+     <para>
+       The prometheus json exporter is now managed by the prometheus community. Together with additional features
+       some backwards incompatibilities were introduced.
+       Most importantly the exporter no longer accepts a fixed command-line parameter to specify the URL of the
+       endpoint serving JSON. It now expects this URL to be passed as an URL parameter, when scraping the exporter's
+       <literal>/probe</literal> endpoint.
+       In the prometheus scrape configuration the scrape target might look like this:
+       <programlisting>
+       http://some.json-exporter.host:7979/probe?target=https://example.com/some/json/endpoint
+       </programlisting>
+     </para>
+     <para>
+       Existing configuration for the exporter needs to be updated, but can partially be re-used.
+       Documentation is available in the upstream repository and a small example for NixOS is available
+       in the corresponding NixOS test.
+     </para>
+     <para>
+       These changes also affect <literal>services.prometheus.exporters.rspamd</literal>, which is
+       just a preconfigured instance of the json exporter.
+     </para>
+     <para>
+       For more information, take a look at the <link xlink:href="https://github.com/prometheus-community/json_exporter">
+       official documentation</link> of the json_exporter.
+     </para>
+   </listitem>
   </itemizedlist>
  </section>
 

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

@@ -236,8 +236,6 @@ in
     services.prometheus.exporters.minio.minioAddress  = mkDefault "http://localhost:9000";
     services.prometheus.exporters.minio.minioAccessKey = mkDefault config.services.minio.accessKey;
     services.prometheus.exporters.minio.minioAccessSecret = mkDefault config.services.minio.secretKey;
-  })] ++ [(mkIf config.services.rspamd.enable {
-    services.prometheus.exporters.rspamd.url = mkDefault "http://localhost:11334/stat";
   })] ++ [(mkIf config.services.prometheus.exporters.rtl_433.enable {
     hardware.rtl-sdr.enable = mkDefault true;
   })] ++ [(mkIf config.services.nginx.enable {

nixos/modules/services/monitoring/prometheus/exporters/json.nix

@@ -4,32 +4,42 @@ with lib;
 
 let
   cfg = config.services.prometheus.exporters.json;
+
 in
 {
   port = 7979;
   extraOpts = {
-    url = mkOption {
-      type = types.str;
-      description = ''
-        URL to scrape JSON from.
-      '';
-    };
     configFile = mkOption {
       type = types.path;
       description = ''
         Path to configuration file.
       '';
     };
-    listenAddress = {}; # not used
   };
   serviceOpts = {
     serviceConfig = {
       ExecStart = ''
-        ${pkgs.prometheus-json-exporter}/bin/prometheus-json-exporter \
-          --port ${toString cfg.port} \
-          ${cfg.url} ${escapeShellArg cfg.configFile} \
+        ${pkgs.prometheus-json-exporter}/bin/json_exporter \
+          --config.file ${escapeShellArg cfg.configFile} \
+          --web.listen-address="${cfg.listenAddress}:${toString cfg.port}" \
           ${concatStringsSep " \\\n  " cfg.extraFlags}
       '';
     };
   };
+  imports = [
+    (mkRemovedOptionModule [ "url" ] ''
+      This option was removed. The URL of the endpoint serving JSON
+      must now be provided to the exporter by prometheus via the url
+      parameter <literal>target</literal>.
+
+      In prometheus a scrape URL would look like this:
+      <programlisting>
+      http://some.json-exporter.host:7979/probe?target=https://example.com/some/json/endpoint
+      </programlisting>
+
+      For more information, take a look at the <link xlink:href="https://github.com/prometheus-community/json_exporter">
+      official documentation</link> of the json_exporter.
+    '')
+     ({ options.warnings = options.warnings; options.assertions = options.assertions; })
+  ];
 }

nixos/modules/services/monitoring/prometheus/exporters/rspamd.nix

@@ -10,7 +10,8 @@ let
       echo '${builtins.toJSON conf}' | ${pkgs.buildPackages.jq}/bin/jq '.' > $out
     '';
 
-  generateConfig = extraLabels: (map (path: {
+  generateConfig = extraLabels: {
+    metrics = (map (path: {
       name = "rspamd_${replaceStrings [ "." " " ] [ "_" "_" ] path}";
       path = "$.${path}";
       labels = extraLabels;
@@ -53,21 +54,11 @@ let
         users = "$.users";
       };
     }];
+  };
 in
 {
   port = 7980;
   extraOpts = {
-    listenAddress = {}; # not used
-
-    url = mkOption {
-      type = types.str;
-      description = ''
-        URL to the rspamd metrics endpoint.
-        Defaults to http://localhost:11334/stat when
-        <option>services.rspamd.enable</option> is true.
-      '';
-    };
-
     extraLabels = mkOption {
       type = types.attrsOf types.str;
       default = {
@@ -84,9 +75,26 @@ in
     };
   };
   serviceOpts.serviceConfig.ExecStart = ''
-    ${pkgs.prometheus-json-exporter}/bin/prometheus-json-exporter \
-      --port ${toString cfg.port} \
-      ${cfg.url} ${prettyJSON (generateConfig cfg.extraLabels)} \
+    ${pkgs.prometheus-json-exporter}/bin/json_exporter \
+      --config.file ${prettyJSON (generateConfig cfg.extraLabels)} \
+      --web.listen-address "${cfg.listenAddress}:${toString cfg.port}" \
       ${concatStringsSep " \\\n  " cfg.extraFlags}
   '';
+
+  imports = [
+    (mkRemovedOptionModule [ "url" ] ''
+      This option was removed. The URL of the rspamd metrics endpoint
+      must now be provided to the exporter by prometheus via the url
+      parameter <literal>target</literal>.
+
+      In prometheus a scrape URL would look like this:
+      <programlisting>
+      http://some.rspamd-exporter.host:7980/probe?target=http://some.rspamd.host:11334/stat
+      </programlisting>
+
+      For more information, take a look at the <link xlink:href="https://github.com/prometheus-community/json_exporter">
+      official documentation</link> of the json_exporter.
+    '')
+     ({ options.warnings = options.warnings; options.assertions = options.assertions; })
+  ];
 }

nixos/tests/prometheus-exporters.nix

@@ -222,10 +222,11 @@ let
       exporterConfig = {
         enable = true;
         url = "http://localhost";
-        configFile = pkgs.writeText "json-exporter-conf.json" (builtins.toJSON [{
-          name = "json_test_metric";
-          path = "$.test";
-        }]);
+        configFile = pkgs.writeText "json-exporter-conf.json" (builtins.toJSON {
+          metrics = [
+            { name = "json_test_metric"; path = "$.test"; }
+          ];
+        });
       };
       metricProvider = {
         systemd.services.prometheus-json-exporter.after = [ "nginx.service" ];
@@ -241,7 +242,9 @@ let
         wait_for_open_port(80)
         wait_for_unit("prometheus-json-exporter.service")
         wait_for_open_port(7979)
-        succeed("curl -sSf localhost:7979/metrics | grep -q 'json_test_metric 1'")
+        succeed(
+            "curl -sSf 'localhost:7979/probe?target=http://localhost' | grep -q 'json_test_metric 1'"
+        )
       '';
     };
 
@@ -659,7 +662,7 @@ let
         wait_for_open_port(11334)
         wait_for_open_port(7980)
         wait_until_succeeds(
-            "curl -sSf localhost:7980/metrics | grep -q 'rspamd_scanned{host=\"rspamd\"} 0'"
+            "curl -sSf 'localhost:7980/probe?target=http://localhost:11334/stat' | grep -q 'rspamd_scanned{host=\"rspamd\"} 0'"
         )
       '';
     };