discourse.plugins.discourse-prometheus: Init

pkgs/servers/web-apps/discourse/plugins/all-plugins.nix

···
   discourse-math = callPackage ./discourse-math {};
   discourse-migratepassword = callPackage ./discourse-migratepassword {};
   discourse-openid-connect = callPackage ./discourse-openid-connect {};
+  discourse-prometheus = callPackage ./discourse-prometheus {};
   discourse-solved = callPackage ./discourse-solved {};
   discourse-spoiler-alert = callPackage ./discourse-spoiler-alert {};
   discourse-yearly-review = callPackage ./discourse-yearly-review {};

pkgs/servers/web-apps/discourse/plugins/discourse-prometheus/Gemfile

···
+# frozen_string_literal: true
+
+source "https://rubygems.org"
+
+git_source(:github) {|repo_name| "https://github.com/#{repo_name}" }
+
+# gem "rails"
+gem 'prometheus_exporter', '0.5.0'

pkgs/servers/web-apps/discourse/plugins/discourse-prometheus/Gemfile.lock

···
+GEM
+  remote: https://rubygems.org/
+  specs:
+    prometheus_exporter (0.5.0)
+
+PLATFORMS
+  ruby
+
+DEPENDENCIES
+  prometheus_exporter (= 0.5.0)
+
+BUNDLED WITH
+   2.1.4

pkgs/servers/web-apps/discourse/plugins/discourse-prometheus/default.nix

···
+{ lib, stdenv, mkDiscoursePlugin, fetchFromGitHub }:
+
+ mkDiscoursePlugin {
+  bundlerEnvArgs.gemdir = ./.;
+  name = "discourse-prometheus";
+  src = fetchFromGitHub {
+    owner = "discourse";
+    repo = "discourse-prometheus";
+    rev = "46260710e8770344af438f86b47409d864a1c499";
+    sha256 = "0nmpi0nysp59x4hyn1c3niypvxw1jkz86acb6m8acacw0c6682k2";
+  };
+
+  patches = [
+    # The metrics collector tries to run git to get the commit id but fails
+    # because we don't run Discourse from a Git repository.
+    ./no-git-version.patch
+    ./spec-import-fix-abi-version.patch
+  ];
+
+  meta = with lib; {
+    homepage = "https://github.com/discourse/discourse-prometheus";
+    maintainers = with maintainers; [ dpausp ];
+    license = licenses.mit;
+    description = "Official Discourse Plugin for Prometheus Monitoring";
+  };
+}

pkgs/servers/web-apps/discourse/plugins/discourse-prometheus/gemset.nix

···
+{
+  prometheus_exporter = {
+    groups = ["default"];
+    platforms = [];
+    source = {
+      remotes = ["https://rubygems.org"];
+      sha256 = "1kmabnxz466zqnyqlzc693ny4l7i0rxvmc0znswvizc0zg4pri80";
+      type = "gem";
+    };
+    version = "0.5.0";
+  };
+}

pkgs/servers/web-apps/discourse/plugins/discourse-prometheus/no-git-version.patch

···
+diff --git a/lib/internal_metric/global.rb b/lib/internal_metric/global.rb
+index 682571b..7bdd431 100644
+--- a/lib/internal_metric/global.rb
++++ b/lib/internal_metric/global.rb
+@@ -30,30 +30,7 @@ module DiscoursePrometheus::InternalMetric
+       @active_app_reqs = 0
+       @queued_app_reqs = 0
+       @fault_logged = {}
+-
+-      begin
+-        @@version = nil
+-
+-        out, error, status = Open3.capture3('git rev-parse HEAD')
+-
+-        if status.success?
+-          @@version ||= out.chomp
+-        else
+-          raise error
+-        end
+-      rescue => e
+-        if defined?(::Discourse)
+-          Discourse.warn_exception(e, message: "Failed to calculate discourse_version_info metric")
+-        else
+-          STDERR.puts "Failed to calculate discourse_version_info metric: #{e}\n#{e.backtrace.join("\n")}"
+-        end
+-
+-        @@retries ||= 10
+-        @@retries -= 1
+-        if @@retries < 0
+-          @@version = -1
+-        end
+-      end
++      @@version = -1
+     end
+ 
+     def collect

pkgs/servers/web-apps/discourse/plugins/discourse-prometheus/spec-import-fix-abi-version.patch

···
+diff --git a/bin/collector b/bin/collector
+index 4fec65e..e59eac7 100755
+--- a/bin/collector
++++ b/bin/collector
+@@ -3,8 +3,10 @@
+ 
+ Process.setproctitle("discourse prometheus-collector")
+ 
++# We need the ABI version {MAJOR}.{MINOR}.0 here.
++abi_version = ENV['GEM_PATH'].split("/")[-1]
+ version = File.read(File.expand_path("../../prometheus_exporter_version", __FILE__)).strip
+-spec_file = File.expand_path("../../gems/#{RUBY_VERSION}/specifications/prometheus_exporter-#{version}.gemspec", __FILE__)
++spec_file = File.expand_path("../../gems/#{abi_version}/specifications/prometheus_exporter-#{version}.gemspec", __FILE__)
+ 
+ spec = Gem::Specification.load spec_file
+ spec.activate

pkgs/servers/web-apps/discourse/update.py

···
         {'name': 'discourse-ldap-auth', 'owner': 'jonmbake'},
         {'name': 'discourse-math'},
         {'name': 'discourse-migratepassword', 'owner': 'discoursehosting'},
+        # We can't update this automatically at the moment because the plugin.rb
+        # tries to load a version number which breaks bundler called by this script.
+        # {'name': 'discourse-prometheus'},
         {'name': 'discourse-solved'},
         {'name': 'discourse-spoiler-alert'},
         {'name': 'discourse-yearly-review'},