implement alternative match-making approach with Lua scripts in Redis

main-server/config/cable.yml

@@ -0,0 +1,10 @@
+development:
+  adapter: async
+
+test:
+  adapter: test
+
+production:
+  adapter: redis
+  url: <%= ENV.fetch("REDIS_URL", "redis://localhost:6380/0") %>
+  channel_prefix: ruby_sea_battle_production

main-server/config/database.yml

@@ -10,15 +10,25 @@ default: &default
   timeout: 5000
 
 development:
-  <<: *default
-  database: storage/development.sqlite3
+  primary:
+    <<: *default
+    database: storage/development.sqlite3
+  queue:
+    <<: *default
+    database: storage/development_queue.sqlite3
+    migrations_paths: db/queue_migrate
 
 # Warning: The database defined as "test" will be erased and
 # re-generated from your development database when you run "rake".
 # Do not set this db to the same as development or production.
 test:
-  <<: *default
-  database: storage/test.sqlite3
+  primary:
+    <<: *default
+    database: storage/test.sqlite3
+  queue:
+    <<: *default
+    database: storage/test_queue.sqlite3
+    migrations_paths: db/queue_migrate
 
 # PostgreSQL for production.
 #
@@ -29,11 +39,22 @@ test:
 #   DB_NAME, DB_USER, DB_PASSWORD, DB_HOST, DB_PORT
 #
 production:
-  adapter: postgresql
-  encoding: unicode
-  pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
-  database: <%= ENV["DB_NAME"] %>
-  username: <%= ENV["DB_USER"] %>
-  password: <%= ENV["DB_PASSWORD"] %>
-  host: <%= ENV["DB_HOST"] %>
-  port: <%= ENV["DB_PORT"] || 5432 %>
+  primary:
+    adapter: postgresql
+    encoding: unicode
+    pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
+    database: <%= ENV["DB_NAME"] %>
+    username: <%= ENV["DB_USER"] %>
+    password: <%= ENV["DB_PASSWORD"] %>
+    host: <%= ENV["DB_HOST"] %>
+    port: <%= ENV["DB_PORT"] || 5432 %>
+  queue:
+    adapter: postgresql
+    encoding: unicode
+    pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
+    database: <%= ENV["QUEUE_DB_NAME"] || ENV["DB_NAME"] %>
+    username: <%= ENV["QUEUE_DB_USER"] || ENV["DB_USER"] %>
+    password: <%= ENV["QUEUE_DB_PASSWORD"] || ENV["DB_PASSWORD"] %>
+    host: <%= ENV["QUEUE_DB_HOST"] || ENV["DB_HOST"] %>
+    port: <%= ENV["QUEUE_DB_PORT"] || ENV["DB_PORT"] || 5432 %>
+    migrations_paths: db/queue_migrate

main-server/config/environments/development.rb

@@ -3,6 +3,11 @@ require "active_support/core_ext/integer/time"
 Rails.application.configure do
   # Settings specified here will take precedence over those in config/application.rb.
 
+  # Run background jobs (e.g. the matchmaking sweeper) through Solid Queue,
+  # supervised by the puma plugin.
+  config.active_job.queue_adapter = :solid_queue
+  config.solid_queue.connects_to = { database: { writing: :queue } }
+
   # Make code changes take effect immediately without server restart.
   config.enable_reloading = true
 

main-server/config/environments/production.rb

@@ -50,7 +50,8 @@ Rails.application.configure do
   config.cache_store = :memory_store
 
   # Replace the default in-process and non-durable queuing backend for Active Job.
-  config.active_job.queue_adapter = :async
+  config.active_job.queue_adapter = :solid_queue
+  config.solid_queue.connects_to = { database: { writing: :queue } }
 
   # Ignore bad email addresses and do not raise email delivery errors.
   # Set this to true and configure the email server for immediate delivery to raise delivery errors.

main-server/config/initializers/matchmaking.rb

@@ -0,0 +1,25 @@
+# Matchmaking configuration. All values can be overridden via environment variables.
+mm = Rails.application.config.x.matchmaking = ActiveSupport::OrderedOptions.new
+
+mm.game_server_url  = ENV.fetch("GAME_SERVER_URL", "ws://localhost:8080")
+mm.default_rating   = ENV.fetch("MATCHMAKING_DEFAULT_RATING", 1000).to_i
+
+# How long a found match (and its game token) stays valid, in seconds.
+mm.match_ttl        = ENV.fetch("MATCHMAKING_MATCH_TTL", 120).to_i
+mm.token_ttl        = ENV.fetch("MATCHMAKING_TOKEN_TTL", 120).to_i
+
+# How long a player waits in the queue before a timeout, in seconds.
+mm.queue_ttl        = ENV.fetch("MATCHMAKING_QUEUE_TTL", 60).to_i
+
+# How long a found (but not yet finalized) pair is kept in the "pending"
+# state before the players are put back into the queue, in seconds.
+mm.pending_ttl      = ENV.fetch("MATCHMAKING_PENDING_TTL", 15).to_i
+
+# Rating tolerance: players within `base_range` are matched immediately;
+# the tolerance grows by `range_per_second` of waiting up to `max_range`.
+mm.base_range       = ENV.fetch("MATCHMAKING_BASE_RANGE", 100).to_i
+mm.range_per_second = ENV.fetch("MATCHMAKING_RANGE_PER_SECOND", 50).to_i
+mm.max_range        = ENV.fetch("MATCHMAKING_MAX_RANGE", 1000).to_i
+
+# How often the background sweep job re-checks the queue, in seconds.
+mm.sweep_interval   = ENV.fetch("MATCHMAKING_SWEEP_INTERVAL", 2).to_i

main-server/config/initializers/redis.rb

@@ -2,6 +2,10 @@
 # Development/test: localhost:6379 (default)
 # Production: set REDIS_URL env variable, e.g. redis://redis.example.com:6379/0
 
+# Use an isolated Redis logical database in tests to avoid clobbering dev data.
+url = ENV.fetch("REDIS_URL", "redis://localhost:6380/0")
+url = url.sub(%r{/\d+$}, "/15") if Rails.env.test?
+
 RedisConnection = ConnectionPool.new(size: 5, timeout: 5) do
-  Redis.new(url: ENV.fetch("REDIS_URL", "redis://localhost:6380/0"))
+  Redis.new(url: url)
 end

main-server/config/puma.rb

@@ -35,7 +35,7 @@ port ENV.fetch("PORT", 3000)
 plugin :tmp_restart
 
 # Run the Solid Queue supervisor inside of Puma for single-server deployments.
-# plugin :solid_queue if ENV["SOLID_QUEUE_IN_PUMA"]
+plugin :solid_queue if ENV["SOLID_QUEUE_IN_PUMA"] || ENV.fetch("RAILS_ENV", "development") == "development"
 
 # Specify the PID file. Defaults to tmp/pids/server.pid in development.
 # In other environments, only set the PID file if requested.

main-server/config/queue.yml

@@ -0,0 +1,18 @@
+default: &default
+  dispatchers:
+    - polling_interval: 1
+      batch_size: 500
+  workers:
+    - queues: "*"
+      threads: 3
+      processes: <%= ENV.fetch("JOB_CONCURRENCY", 1) %>
+      polling_interval: 1
+
+development:
+  <<: *default
+
+test:
+  <<: *default
+
+production:
+  <<: *default

main-server/config/recurring.yml

@@ -0,0 +1,18 @@
+# examples:
+#   periodic_cleanup:
+#     class: CleanSoftDeletedRecordsJob
+#     queue: background
+#     args: [ 1000, { batch_size: 500 } ]
+#     schedule: every hour
+#   periodic_cleanup_with_command:
+#     command: "SoftDeletedRecord.due.delete_all"
+#     priority: 2
+#     schedule: at 5am every day
+
+production:
+  matchmaking_sweep:
+    class: MatchmakingSweepJob
+    schedule: every <%= ENV.fetch("MATCHMAKING_SWEEP_INTERVAL", 2) %> seconds
+  clear_solid_queue_finished_jobs:
+    command: "SolidQueue::Job.clear_finished_in_batches(sleep_between_batches: 0.3)"
+    schedule: every hour at minute 12

main-server/config/routes.rb

@@ -1,12 +1,16 @@
 Rails.application.routes.draw do
+  mount ActionCable.server => "/cable"
+
   namespace :api do
     post   "register", to: "registrations#create"
     post   "login",    to: "sessions#create"
     delete "logout",   to: "sessions#destroy"
     get    "me",       to: "sessions#me"
 
-    post   "matchmaking", to: "matchmaking#create"
     delete "matchmaking", to: "matchmaking#destroy"
+
+  # Matchmaking starts over the MatchmakingChannel WebSocket
+  # (see app/channels/matchmaking_channel.rb).
   end
 
   # Reveal health status on /up that returns 200 if the app boots with no exceptions, otherwise 500.