Log database errors

Previously all `PG::ConnectionBad` errors were quietly swallowed. We now
pass along a logger so that we can see when these errors occur.

Closes https://gitlab.com/gitlab-org/gitlab-exporter/-/issues/72

lib/gitlab_exporter/database/base.rb

@@ -16,8 +16,9 @@ module GitLab
           end
         end
 
-        def initialize(args)
+        def initialize(args, logger: nil)
           @connection_string = args[:connection_string]
+          @logger = logger
         end
 
         def run
@@ -33,10 +34,14 @@ module GitLab
             begin
               yield conn
             rescue PG::UnableToSend => e
+              @logger.warn "Error sending to the database: #{e}" if @logger
               conn.reset
               raise e
             end
           end
+        rescue PG::Error => e
+          @logger.error "Error connecting to the database: #{e}" if @logger
+          raise e
         end
       end
     end

lib/gitlab_exporter/database/ci_builds.rb

@@ -262,8 +262,8 @@ module GitLab
 
         DEFAULT_UNARCHIVED_TRACES_OFFSET_MINUTES = 1440
 
-        def initialize(opts)
-          super(opts)
+        def initialize(opts, logger: nil)
+          super(opts, logger: logger)
 
           @allowed_repeated_commands_count = opts[:allowed_repeated_commands_count]
           @created_builds_counting_disabled = opts[:created_builds_counting_disabled]
@@ -417,14 +417,14 @@ module GitLab
 
       # The prober which is called when gathering metrics
       class CiBuildsProber
-        def initialize(opts, metrics: PrometheusMetrics.new)
+        def initialize(opts, metrics: PrometheusMetrics.new, logger: nil)
           @metrics = metrics
 
           collector_opts = { connection_string: opts[:connection_string],
                              allowed_repeated_commands_count: opts[:allowed_repeated_commands_count],
                              created_builds_counting_disabled: opts[:created_builds_counting_disabled],
                              unarchived_traces_offset_minutes: opts[:unarchived_traces_offset_minutes] }
-          @collector = CiBuildsCollector.new(collector_opts)
+          @collector = CiBuildsCollector.new(collector_opts, logger: logger)
         end
 
         def probe_db

lib/gitlab_exporter/database/remote_mirrors.rb

@@ -35,7 +35,7 @@ module GitLab
 
       # The prober which is called when gathering metrics
       class RemoteMirrorsProber
-        def initialize(opts, metrics: PrometheusMetrics.new)
+        def initialize(opts, metrics: PrometheusMetrics.new, logger: nil)
           @metrics = metrics
           @collector = RemoteMirrorsCollector.new(
             connection_string: opts[:connection_string],

lib/gitlab_exporter/database/row_count.rb

@@ -212,7 +212,7 @@ module GitLab
 
       # The prober which is called when gathering metrics
       class RowCountProber
-        def initialize(opts, metrics: PrometheusMetrics.new)
+        def initialize(opts, metrics: PrometheusMetrics.new, logger: nil)
           @metrics = metrics
           @collector = RowCountCollector.new(
             connection_string: opts[:connection_string],

lib/gitlab_exporter/database/tuple_stats.rb

@@ -25,9 +25,9 @@ module GitLab
 
       # Probes the DB specified by opts[:connection_string] for tuple stats, then converts them to metrics
       class TuplesProber
-        def initialize(opts, metrics: PrometheusMetrics.new)
+        def initialize(opts, metrics: PrometheusMetrics.new, logger: nil)
           @metrics   = metrics
-          @collector = TupleStatsCollector.new(connection_string: opts[:connection_string])
+          @collector = TupleStatsCollector.new(connection_string: opts[:connection_string], logger: logger)
         end
 
         def probe_db

lib/gitlab_exporter/git.rb

@@ -62,7 +62,7 @@ module GitLab
     # Optionally takes a metrics object which by default is a PrometheusMetrics, useful to change the
     # metrics writer to something else.
     class GitProber
-      def initialize(opts, metrics: PrometheusMetrics.new)
+      def initialize(opts, metrics: PrometheusMetrics.new, logger: nil)
         @metrics = metrics
         @labels = opts[:labels] || {}
         @git = Git.new(opts[:source])
@@ -85,7 +85,7 @@ module GitLab
 
     # A special prober for git processes
     class GitProcessProber
-      def initialize(opts, metrics: PrometheusMetrics.new)
+      def initialize(opts, metrics: PrometheusMetrics.new, logger: nil)
         @opts    = opts
         @metrics = metrics
       end

lib/gitlab_exporter/prober.rb

@@ -2,9 +2,10 @@ module GitLab
   module Exporter
     # A class to combine multiple probers into one
     class Prober
-      def initialize(prober_opts, metrics: PrometheusMetrics.new)
+      def initialize(prober_opts, metrics: PrometheusMetrics.new, logger: nil)
         @prober_opts = prober_opts
         @metrics     = metrics
+        @logger      = logger
 
         resolve_prober_classes
       end
@@ -12,7 +13,7 @@ module GitLab
       def probe_all
         @prober_opts.each do |_probe_name, params|
           Utils.wrap_in_array(params[:opts]).each do |opts|
-            prober = params[:class].new(opts, metrics: @metrics)
+            prober = params[:class].new(opts, metrics: @metrics, logger: @logger)
             params[:methods].each do |meth|
               prober.send(meth)
             end

lib/gitlab_exporter/process.rb

@@ -59,7 +59,7 @@ module GitLab
 
     # Probes a process for info then writes metrics to a target
     class ProcessProber
-      def initialize(options, metrics: PrometheusMetrics.new)
+      def initialize(options, metrics: PrometheusMetrics.new, logger: nil)
         @metrics = metrics
         @name    = options[:name]
         @pids    = if options[:pid_or_pattern] =~ /^\d+$/

lib/gitlab_exporter/sidekiq.rb

@@ -10,9 +10,10 @@ module GitLab
       QUEUE_JOB_STATS_SCRIPT = File.read(File.expand_path("#{__FILE__}/../sidekiq_queue_job_stats.lua")).freeze
       QUEUE_JOB_STATS_SHA    = Digest::SHA1.hexdigest(QUEUE_JOB_STATS_SCRIPT).freeze
 
-      def initialize(opts, metrics: PrometheusMetrics.new)
+      def initialize(opts, metrics: PrometheusMetrics.new, logger: nil)
         @opts    = opts
         @metrics = metrics
+        @logger  = logger
 
         Sidekiq.configure_client do |config|
           config.redis = redis_options

lib/gitlab_exporter/web_exporter.rb

@@ -42,6 +42,11 @@ module GitLab
 
           memory_threshold = (config[:server] && config[:server][:memory_threshold]) || 1024
           use MemoryKillerMiddleware, memory_threshold
+          use Rack::Logger
+        end
+
+        def logger
+          request.logger
         end
 
         def setup_server(config)
@@ -62,7 +67,7 @@ module GitLab
 
             get "/#{probe_name}" do
               content_type "text/plain; version=0.0.4"
-              prober = Prober.new(opts, metrics: PrometheusMetrics.new(include_timestamp: false))
+              prober = Prober.new(opts, metrics: PrometheusMetrics.new(include_timestamp: false), logger: logger)
 
               prober.probe_all
               prober.write_to(response)