DEV: Add message-bus analysis script (discourse#15979)

This will count how many messages are published per-channel and produce a table of channels ordered by 'most messages'

script/analyse_message_bus.rb

@@ -0,0 +1,63 @@
+# frozen_string_literal: true
+
+require File.expand_path("../../config/environment", __FILE__)
+
+channel_counters = Hash.new(0)
+messages_seen = 0
+
+wait_seconds = ARGV[0]&.to_i || 10
+
+puts "Counting messages for #{wait_seconds} seconds..."
+
+print 'Seen 0 messages'
+t = Thread.new do
+  MessageBus.backend_instance.global_subscribe do |m|
+    channel = m.channel
+    if channel.start_with?("/distributed_hash")
+      payload = JSON.parse(m.data)["data"]
+      info = payload["hash_key"]
+      # info += ".#{payload["key"]}" # Uncomment if you need more granular info
+      channel += " (#{info})"
+    end
+
+    channel_counters[channel] += 1
+    messages_seen += 1
+
+    print "\rSeen #{messages_seen} messages from #{channel_counters.size} channels"
+  end
+end
+
+sleep wait_seconds
+
+MessageBus.backend_instance.global_unsubscribe
+t.join
+
+puts
+puts "All done!"
+
+if messages_seen == 0
+  puts "Saw no messages :("
+  exit 1
+end
+
+puts
+puts
+sorted_results = channel_counters.sort_by { |k, v| -v }
+max_channel_name_length = channel_counters.keys.max_by { |name| name.length }.length
+max_count_length = channel_counters.values.max_by { |val| val.to_s.length }.to_s.length
+
+max_channel_name_length = ["channel".length, max_channel_name_length].max
+max_count_length = ["message count".length, max_count_length, messages_seen.to_s.length].max
+
+puts "| #{"channel".ljust(max_channel_name_length)} | #{"message count".rjust(max_count_length)} |"
+puts "|#{"-" * (max_channel_name_length + 2)}|#{"-" * (max_count_length + 2)}|"
+
+result_count = 10
+sorted_results.first(result_count).each do |name, value|
+  name = "`#{name}`"
+  puts "| #{name.ljust(max_channel_name_length)} | #{value.to_s.rjust(max_count_length)} |"
+end
+other_count = messages_seen - sorted_results.first(result_count).sum { |k, v| v }
+puts "| #{"(other)".ljust(max_channel_name_length)} | #{other_count.to_s.rjust(max_count_length)} |"
+puts "|#{" " * (max_channel_name_length + 2)}|#{" " * (max_count_length + 2)}|"
+puts "| #{"TOTAL".ljust(max_channel_name_length)} | #{messages_seen.to_s.rjust(max_count_length)} |"