Config: Reload configuration on modification

It detects changes on the config.yml automtically if invidious is
running on linux. If not, the configuration can be reloaded using
`kill -s HUP $(pidof invidious)` or any other tool that sends a SIGHUP
signal to the invidious process.

Closes iv-org#16

shard.lock

@@ -20,6 +20,10 @@ shards:
     git: https://github.com/crystal-loot/exception_page.git
     version: 0.2.2
 
+  inotify:
+    git: https://github.com/petoem/inotify.cr.git
+    version: 1.0.3
+
   kemal:
     git: https://github.com/kemalcr/kemal.git
     version: 1.1.2

shard.yml

@@ -30,6 +30,9 @@ dependencies:
     version: ~> 0.1.1
   redis:
     github: stefanwille/crystal-redis
+  inotify:
+    github: petoem/inotify.cr
+    version: 1.0.3
 
 development_dependencies:
   spectator:

src/invidious.cr

@@ -32,6 +32,7 @@ require "yaml"
 require "compress/zip"
 require "protodec/utils"
 require "redis"
+require "inotify"
 
 require "./invidious/database/*"
 require "./invidious/database/migrations/*"
@@ -58,7 +59,20 @@ end
 # Simple alias to make code easier to read
 alias IV = Invidious
 
-CONFIG   = Config.load
+CONFIG = Config.load
+
+Signal::HUP.trap do
+  Config.reload
+end
+
+{% if flag?(:linux) %}
+if CONFIG.reload_config_automatically
+    Inotify.watch("config/config.yml") do |event|
+      Config.reload
+    end
+end
+{% end %}
+
 HMAC_KEY = CONFIG.hmac_key
 
 PG_DB    = DB.open CONFIG.database_url

src/invidious/config.cr

@@ -95,6 +95,8 @@ class Config
   property hmac_key : String = ""
   # Domain to be used for links to resources on the site where an absolute URL is required
   property domain : String?
+  # Materialious redirects
+  property materialious_domain : String?
   # Alternative domains. You can add other domains, like TOR and I2P addresses
   property alternative_domains : Array(String) = [] of String
   property donation_url : String?
@@ -190,9 +192,11 @@ class Config
   property pubsub_domain : String = ""
 
   property ignore_user_tokens : Bool = false
+
+  {% if flag?(:linux) %}
+  property reload_config_automatically : Bool = true
+  {% end %}
 
-  # Materialious redirects
-  property materialious_domain : String?
 
   def disabled?(option)
     case disabled = CONFIG.disable_proxy
@@ -209,6 +213,25 @@ class Config
     end
   end
 
+  def self.reload
+    LOGGER.info("Config: Reloading configuration")
+    # Load config from file or YAML string env var
+    env_config_file = "INVIDIOUS_CONFIG_FILE"
+    env_config_yaml = "INVIDIOUS_CONFIG"
+    config_file = ENV.has_key?(env_config_file) ? ENV.fetch(env_config_file) : "config/config.yml"
+    config_yaml = ENV.has_key?(env_config_yaml) ? ENV.fetch(env_config_yaml) : File.read(config_file)
+    begin
+      config = Config.from_yaml(config_yaml)
+    rescue ex
+      LOGGER.error("Config: Error when reloading configuration: '#{ex.message}'")
+      config = CONFIG
+    end
+    {% for ivar in Config.instance_vars %}
+	  CONFIG.{{ivar}} = config.{{ivar}}
+	{% end %}
+	LOGGER.info("Config: Reload successfull")
+  end
+
   def self.load
     # Load config from file or YAML string env var
     env_config_file = "INVIDIOUS_CONFIG_FILE"