1 files changed, 107 insertions, 0 deletions
diff --git a/lib/backup/database_configuration.rb b/lib/backup/database_configuration.rb
new file mode 100644
index 00000000000..1a6a476f9c1
--- /dev/null
+++ b/lib/backup/database_configuration.rb
@@ -0,0 +1,107 @@
+# frozen_string_literal: true
+
+module Backup
+  class DatabaseConfiguration
+    # Connection name is the key used in `config/database.yml` for multi-database connection configuration
+    #
+    # @return [String]
+    attr_reader :connection_name
+
+    # ActiveRecord base model that is configured to connect to the database identified by connection_name key
+    #
+    # @return [ActiveRecord::Base]
+    attr_reader :source_model
+
+    # Initializes configuration
+    #
+    # @param [String] connection_name the key from `database.yml` for multi-database connection configuration
+    def initialize(connection_name)
+      @connection_name = connection_name
+      @source_model = Gitlab::Database.database_base_models_with_gitlab_shared[connection_name] ||
+        Gitlab::Database.database_base_models_with_gitlab_shared['main']
+      @activerecord_database_config = ActiveRecord::Base.configurations.find_db_config(connection_name)
+    end
+
+    # ENV variables that can override each database configuration
+    # These are used along with OVERRIDE_PREFIX and database name
+    # @see #process_config_overrides!
+    SUPPORTED_OVERRIDES = {
+      username: 'PGUSER',
+      host: 'PGHOST',
+      port: 'PGPORT',
+      password: 'PGPASSWORD',
+      # SSL
+      sslmode: 'PGSSLMODE',
+      sslkey: 'PGSSLKEY',
+      sslcert: 'PGSSLCERT',
+      sslrootcert: 'PGSSLROOTCERT',
+      sslcrl: 'PGSSLCRL',
+      sslcompression: 'PGSSLCOMPRESSION'
+    }.freeze
+
+    # Prefixes used for ENV variables overriding database configuration
+    OVERRIDE_PREFIXES = %w[GITLAB_BACKUP_ GITLAB_OVERRIDE_].freeze
+
+    # Return the HashConfig for the database
+    #
+    # @return [ActiveRecord::DatabaseConfigurations::HashConfig]
+    def activerecord_configuration
+      ActiveRecord::DatabaseConfigurations::HashConfig.new(
+        @activerecord_database_config.env_name,
+        connection_name,
+        activerecord_variables
+      )
+    end
+
+    # Return postgres ENV variable values for current database with overrided values
+    #
+    # @return[Hash<String,String>] hash of postgres ENV variables
+    def pg_env_variables
+      process_config_overrides! unless @pg_env_variables
+
+      @pg_env_variables
+    end
+
+    # Return activerecord configuration values for current database with overrided values
+    #
+    # @return[Hash<String,String>] activerecord database.yml configuration compatible values
+    def activerecord_variables
+      process_config_overrides! unless @activerecord_variables
+
+      @activerecord_variables
+    end
+
+    private
+
+    def process_config_overrides!
+      @activerecord_variables = original_activerecord_config
+      @pg_env_variables = {}
+
+      SUPPORTED_OVERRIDES.each do |config_key, env_variable_name|
+        # This enables the use of different PostgreSQL settings in
+        # case PgBouncer is used. PgBouncer clears the search path,
+        # which wreaks havoc on Rails if connections are reused.
+        OVERRIDE_PREFIXES.each do |override_prefix|
+          override_all = "#{override_prefix}#{env_variable_name}"
+          override_db = "#{override_prefix}#{connection_name.upcase}_#{env_variable_name}"
+          val = ENV[override_db].presence ||
+            ENV[override_all].presence ||
+            @activerecord_variables[config_key].to_s.presence
+
+          next unless val
+
+          @pg_env_variables[env_variable_name] = val
+          @activerecord_variables[config_key] = val
+        end
+      end
+    end
+
+    # Return the database configuration from rails config/database.yml file
+    # in the format expected by ActiveRecord::DatabaseConfigurations::HashConfig
+    #
+    # @return [Hash] configuration hash
+    def original_activerecord_config
+      @activerecord_database_config.configuration_hash.dup
+    end
+  end
+end