Expose database connection pool settings

config/config.example.yml

@@ -15,6 +15,93 @@ db:
   port: 5432
   dbname: invidious
 
+
+  ## -----------------------------------
+  ## Database connection pool settings
+  ## -----------------------------------
+
+  ##
+  ## The maximum allowed number of connections within the connection pool.
+  ## When this number is reached and no connections are free, Invidious will
+  ## wait for up to `checkout_timeout` before raising an exception.
+  ##
+  ## Note: Setting to 0 will disable this limit and allow the the pool to
+  ## grow indefinitely.
+  ##
+  ## Accepted values: a positive integer
+  ## Default: 100
+  ##
+  #max_pool_size: 100
+
+  ##
+  ## How many idle connections should be allowed to exist within the connection pool.
+  ##
+  ## There is no concept of whether a connection is closed or open, or how long it has been
+  ## idly sitting by. Instead Idle connections are defined as any connections that are not
+  ## currently being used. When this number is exceeded but the amount of connections is still
+  ## under max_pool_size, new connections will be created on a checkout but immediately closed
+  ## and destroyed during an release operation.
+  ##
+  ## For the most part, this should just be set to the same number as the `max_pool_size`.
+  ##
+  ## Accepted values: a positive integer
+  ## Default: 100
+  ##
+  #max_idle_pool_size: 100
+
+  ##
+  ## The amount of connections to establish on start-up.
+  ##
+  ## When Invidious starts up, the database connection pool is immediately populated
+  ## with this many connections. This could allow an instance to avoid potentially experiencing
+  ## any degraded service during start-up; since a good amount of connections will be available
+  ## from the start rather than needing to be created on the fly as requests come in.
+  ##
+  ##
+  ## Accepted values: a positive integer
+  ## Default: 1
+  ##
+  #initial_pool_size  : 1
+
+  ##
+  ## How long to wait (in seconds) before timing out during a checkout
+  ##
+  ## Accepted values: a positive float
+  ## Default: 5.0
+  ##
+  #checkout_timeout: 5.0
+
+  ##
+  ## How many attempts to retry a connection
+  ##
+  ## This allows Invidious to gracefully handle network problems that can
+  ## cause a connection to fail or be unable to get established in the first
+  ## place.
+  ##
+  ## Note: The mechanisms of the underlying library will first try to reuse all the
+  ## currently available idle connections within the pool, as well as one additional attempt,
+  ## at no delay. Afterwards, it will began counting down the `retry_attempts` and wait
+  ## `retry_delay` seconds between each attempt.
+  ##
+  ## This heuristic ensures that unnecessary new connections are not being made for no reason, and
+  ## in the event of widespread network failures, will help to throw out dead connections from the
+  ## pool.
+  ##
+  ## Accepted values: a positive integer
+  ## Default: 5
+  ##
+  #retry_attempts: 5
+
+  ##
+  ## How long to wait (in seconds) between each retry attempt
+  ##
+  ## Note: See description for `retry_attempts` for more information
+  ##
+  ## Accepted values: a positive float
+  ## Default: 1.0
+  ##
+  #retry_delay: 1.0
+
 ##
 ## Database configuration using a single URI. This is an
 ## alternative to the 'db' parameter above. If both forms
@@ -26,6 +113,10 @@ db:
 ## and append the 'host' parameter. E.g:
 ##   postgres://kemal:kemal@/invidious?host=/var/run/postgresql
 ##
+## You can also configure the connection pool here by
+## adding query parameters with the same name as the value you
+## want to change.
+##
 ## Accepted values: a postgres:// URI
 ## Default: postgres://kemal:kemal@localhost:5432/invidious
 ##

src/invidious/config.cr

@@ -6,6 +6,52 @@ struct DBConfig
   property host : String
   property port : Int32
   property dbname : String
+
+  # How many connections to construct on start-up, and keep it there.
+  property initial_pool_size : Int32 = 1
+  # The maximum size of the connection pool
+  property max_pool_size : Int32 = 100
+  # The maximum amount of idle connections within the pool
+  # idle connections are defined as created connections that are
+  # sitting around in the pool. Exceeding this number will cause new connections
+  # to be created on checkout and then simply dropped on release, till the maximum pool size
+  # from which there will be a checkout timeout.
+  property max_idle_pool_size : Int32 = 100
+  # The maximum amount of seconds to wait for a connection to become
+  # available when all connections can be checked out, and the pool has
+  # reached its maximum size.
+  property checkout_timeout : Float32 = 5.0
+  # The number of tries allowed to establish a connection, reconnect, or retry
+  # the command in case of any network errors.
+  property retry_attempts : Int32 = 5
+  # The number of seconds between each retry
+  property retry_delay : Float32 = 1.0
+
+  def to_url
+    URI.new(
+      scheme: "postgres",
+      user: user,
+      password: password,
+      host: host,
+      port: port,
+      path: dbname,
+      query: get_connection_pool_query_string
+    )
+  end
+
+  # Creates the query parameters for configuring the connection pool
+  private def get_connection_pool_query_string
+    {% begin %}
+      {% pool_vars = @type.instance_vars.reject { |v| {"user", "password", "host", "port", "dbname"}.includes?(v.name.stringify) } %}
+      {% raise "Error unable to isolate database connection pool properties" if pool_vars.size > 6 %}
+
+      URI::Params.build do | build |
+        {% for vars in pool_vars %}
+          build.add {{vars.name.stringify}}, {{vars.name}}.to_s
+        {% end %}
+      end
+    {% end %}
+  end
 end
 
 struct SocketBindingConfig
@@ -287,18 +333,23 @@ class Config
     # Build database_url from db.* if it's not set directly
     if config.database_url.to_s.empty?
       if db = config.db
-        config.database_url = URI.new(
-          scheme: "postgres",
-          user: db.user,
-          password: db.password,
-          host: db.host,
-          port: db.port,
-          path: db.dbname,
-        )
+        config.database_url = db.to_url
       else
         puts "Config: Either database_url or db.* is required"
         exit(1)
       end
+    else
+      # Add default connection pool settings as needed
+      db_url_query_params = config.database_url.query_params
+
+      {% begin %}
+        {% pool_vars = DBConfig.instance_vars.reject { |v| {"user", "password", "host", "port", "dbname"}.includes?(v.name.stringify) } %}
+        {% for vars in pool_vars %}
+          db_url_query_params[{{vars.name.stringify}}] = db_url_query_params[{{vars.name.stringify}}]? || {{vars.default_value}}.to_s
+        {% end %}
+      {% end %}
+
+      config.database_url.query_params = db_url_query_params
     end
 
     # Check if the socket configuration is valid